greenplumn postgres_fdw 源码
greenplumn postgres_fdw 代码
文件路径：/contrib/postgres_fdw/postgres_fdw.c
/*-------------------------------------------------------------------------
*
* postgres_fdw.c
* Foreign-data wrapper for remote PostgreSQL servers
*
* Portions Copyright (c) 2012-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/postgres_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/pg_class.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/float.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/sampling.h"
#include "utils/selfuncs.h"
PG_MODULE_MAGIC;
/* Default CPU cost to start up a foreign query. */
#define DEFAULT_FDW_STARTUP_COST 100.0
/* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */
#define DEFAULT_FDW_TUPLE_COST 0.01
/* If no remote estimates, assume a sort costs 20% extra */
#define DEFAULT_FDW_SORT_MULTIPLIER 1.2
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
* These items are indexed with the enum FdwScanPrivateIndex, so an item
* can be fetched with list_nth(). For example, to get the SELECT statement:
* sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
*/
enum FdwScanPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwScanPrivateSelectSql,
/* Integer list of attribute numbers retrieved by the SELECT */
FdwScanPrivateRetrievedAttrs,
/* Integer representing the desired fetch_size */
FdwScanPrivateFetchSize,
/*
* String describing join i.e. names of relations being joined and types
* of join, added when the scan is join
*/
FdwScanPrivateRelations
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ModifyTable node referencing a postgres_fdw foreign table. We store:
*
* 1) INSERT/UPDATE/DELETE statement text to be sent to the remote server
* 2) Integer list of target attribute numbers for INSERT/UPDATE
* (NIL for a DELETE)
* 3) Boolean flag showing if the remote query has a RETURNING clause
* 4) Integer list of attribute numbers retrieved by RETURNING, if any
*/
enum FdwModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwModifyPrivateUpdateSql,
/* Integer list of target attribute numbers for INSERT/UPDATE */
FdwModifyPrivateTargetAttnums,
/* has-returning flag (as an integer Value node) */
FdwModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwModifyPrivateRetrievedAttrs
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ForeignScan node that modifies a foreign table directly. We store:
*
* 1) UPDATE/DELETE statement text to be sent to the remote server
* 2) Boolean flag showing if the remote query has a RETURNING clause
* 3) Integer list of attribute numbers retrieved by RETURNING, if any
* 4) Boolean flag showing if we set the command es_processed
*/
enum FdwDirectModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwDirectModifyPrivateUpdateSql,
/* has-returning flag (as an integer Value node) */
FdwDirectModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwDirectModifyPrivateRetrievedAttrs,
/* set-processed flag (as an integer Value node) */
FdwDirectModifyPrivateSetProcessed
};
/*
* Execution state of a foreign scan using postgres_fdw.
*/
typedef struct PgFdwScanState
{
Relation rel; /* relcache entry for the foreign table. NULL
* for a foreign join scan. */
TupleDesc tupdesc; /* tuple descriptor of scan */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* extracted fdw_private data */
char *query; /* text of SELECT command */
List *retrieved_attrs; /* list of retrieved attribute numbers */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
unsigned int cursor_number; /* quasi-unique ID for my cursor */
bool cursor_exists; /* have we created the cursor? */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
HeapTuple *tuples; /* array of currently-retrieved tuples */
int num_tuples; /* # of tuples in array */
int next_tuple; /* index of next one to return */
/* batch-level state, for optimizing rewinds and avoiding useless fetch */
int fetch_ct_2; /* Min(# of fetches done, 2) */
bool eof_reached; /* true if last fetch reached EOF */
/* working memory contexts */
MemoryContext batch_cxt; /* context holding current batch of tuples */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
int fetch_size; /* number of tuples per fetch */
} PgFdwScanState;
/*
* Execution state of a foreign insert/update/delete operation.
*/
typedef struct PgFdwModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
char *p_name; /* name of prepared statement, if created */
/* extracted fdw_private data */
char *query; /* text of INSERT/UPDATE/DELETE command */
List *target_attrs; /* list of target attribute numbers */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
/* info about parameters for prepared statement */
AttrNumber ctidAttno; /* attnum of input resjunk ctid column */
int p_nums; /* number of parameters to transmit */
FmgrInfo *p_flinfo; /* output conversion functions for them */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
/* for update row movement if subplan result rel */
struct PgFdwModifyState *aux_fmstate; /* foreign-insert state, if
* created */
} PgFdwModifyState;
/*
* Execution state of a foreign scan that modifies a foreign table directly.
*/
typedef struct PgFdwDirectModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* extracted fdw_private data */
char *query; /* text of UPDATE/DELETE command */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
bool set_processed; /* do we set the command es_processed? */
/* for remote query execution */
PGconn *conn; /* connection for the update */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
PGresult *result; /* result for query */
int num_tuples; /* # of result tuples */
int next_tuple; /* index of next one to return */
Relation resultRel; /* relcache entry for the target relation */
AttrNumber *attnoMap; /* array of attnums of input user columns */
AttrNumber ctidAttno; /* attnum of input ctid column */
AttrNumber oidAttno; /* attnum of input oid column */
bool hasSystemCols; /* are there system columns of resultRel? */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwDirectModifyState;
/*
* Workspace for analyzing a foreign table.
*/
typedef struct PgFdwAnalyzeState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
List *retrieved_attrs; /* attr numbers retrieved by query */
/* collected sample rows */
HeapTuple *rows; /* array of size targrows */
int targrows; /* target # of sample rows */
int numrows; /* # of sample rows collected */
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
ReservoirStateData rstate; /* state for reservoir sampling */
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwAnalyzeState;
/*
* This enum describes what's kept in the fdw_private list for a ForeignPath.
* We store:
*
* 1) Boolean flag showing if the remote query has the final sort
* 2) Boolean flag showing if the remote query has the LIMIT clause
*/
enum FdwPathPrivateIndex
{
/* has-final-sort flag (as an integer Value node) */
FdwPathPrivateHasFinalSort,
/* has-limit flag (as an integer Value node) */
FdwPathPrivateHasLimit
};
/* Struct for extra information passed to estimate_path_cost_size() */
typedef struct
{
PathTarget *target;
bool has_final_sort;
bool has_limit;
double limit_tuples;
int64 count_est;
int64 offset_est;
} PgFdwPathExtraData;
/*
* Identify the attribute where data conversion fails.
*/
typedef struct ConversionLocation
{
Relation rel; /* foreign table's relcache entry. */
AttrNumber cur_attno; /* attribute number being processed, or 0 */
/*
* In case of foreign join push down, fdw_scan_tlist is used to identify
* the Var node corresponding to the error location and
* fsstate->ss.ps.state gives access to the RTEs of corresponding relation
* to get the relation name and attribute name.
*/
ForeignScanState *fsstate;
} ConversionLocation;
/* Callback argument for ec_member_matches_foreign */
typedef struct
{
Expr *current; /* current expr, or NULL if not yet found */
List *already_used; /* expressions already dealt with */
} ec_member_foreign_arg;
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(postgres_fdw_handler);
/*
* FDW callback routines
*/
static void postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static void postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static ForeignScan *postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *foreignrel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan);
static void postgresBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node);
static void postgresReScanForeignScan(ForeignScanState *node);
static void postgresEndForeignScan(ForeignScanState *node);
static void postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation);
static List *postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags);
static TupleTableSlot *postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo);
static void postgresBeginForeignInsert(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo);
static void postgresEndForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo);
static int postgresIsForeignRelUpdatable(Relation rel);
static bool postgresPlanDirectModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void postgresBeginDirectModify(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateDirectModify(ForeignScanState *node);
static void postgresEndDirectModify(ForeignScanState *node);
static void postgresExplainForeignScan(ForeignScanState *node,
ExplainState *es);
static void postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es);
static void postgresExplainDirectModify(ForeignScanState *node,
ExplainState *es);
static bool postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages);
static List *postgresImportForeignSchema(ImportForeignSchemaStmt *stmt,
Oid serverOid);
static void postgresGetForeignJoinPaths(PlannerInfo *root,
RelOptInfo *joinrel,
RelOptInfo *outerrel,
RelOptInfo *innerrel,
JoinType jointype,
JoinPathExtraData *extra);
static bool postgresRecheckForeignScan(ForeignScanState *node,
TupleTableSlot *slot);
static void postgresGetForeignUpperPaths(PlannerInfo *root,
UpperRelationKind stage,
RelOptInfo *input_rel,
RelOptInfo *output_rel,
void *extra);
static int greenplumCheckIsGreenplum(UserMapping *user);
/*
* Helper functions
*/
static void estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *foreignrel,
List *param_join_conds,
List *pathkeys,
PgFdwPathExtraData *fpextra,
double *p_rows, int *p_width,
Cost *p_startup_cost, Cost *p_total_cost);
static void get_remote_estimate(const char *sql,
PGconn *conn,
double *rows,
int *width,
Cost *startup_cost,
Cost *total_cost);
static void adjust_foreign_grouping_path_cost(PlannerInfo *root,
List *pathkeys,
double retrieved_rows,
double width,
double limit_tuples,
Cost *p_startup_cost,
Cost *p_run_cost);
static bool ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, EquivalenceMember *em,
void *arg);
static void create_cursor(ForeignScanState *node);
static void fetch_more_data(ForeignScanState *node);
static void close_cursor(PGconn *conn, unsigned int cursor_number);
static PgFdwModifyState *create_foreign_modify(EState *estate,
RangeTblEntry *rte,
ResultRelInfo *resultRelInfo,
CmdType operation,
Plan *subplan,
char *query,
List *target_attrs,
bool has_returning,
List *retrieved_attrs);
static TupleTableSlot *execute_foreign_modify(EState *estate,
ResultRelInfo *resultRelInfo,
CmdType operation,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void prepare_foreign_modify(PgFdwModifyState *fmstate);
static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot);
static void store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res);
static void finish_foreign_modify(PgFdwModifyState *fmstate);
static List *build_remote_returning(Index rtindex, Relation rel,
List *returningList);
static void rebuild_fdw_scan_tlist(ForeignScan *fscan, List *tlist);
static void execute_dml_stmt(ForeignScanState *node);
static TupleTableSlot *get_returning_data(ForeignScanState *node);
static void init_returning_filter(PgFdwDirectModifyState *dmstate,
List *fdw_scan_tlist,
Index rtindex);
static TupleTableSlot *apply_returning_filter(PgFdwDirectModifyState *dmstate,
TupleTableSlot *slot,
EState *estate);
static void prepare_query_params(PlanState *node,
List *fdw_exprs,
int numParams,
FmgrInfo **param_flinfo,
List **param_exprs,
const char ***param_values);
static void process_query_params(ExprContext *econtext,
FmgrInfo *param_flinfo,
List *param_exprs,
const char **param_values);
static int postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows);
static void analyze_row_processor(PGresult *res, int row,
PgFdwAnalyzeState *astate);
static HeapTuple make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
List *retrieved_attrs,
ForeignScanState *fsstate,
MemoryContext temp_context);
static void conversion_error_callback(void *arg);
static bool foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel,
JoinType jointype, RelOptInfo *outerrel, RelOptInfo *innerrel,
JoinPathExtraData *extra);
static bool foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel,
Node *havingQual);
static List *get_useful_pathkeys_for_relation(PlannerInfo *root,
RelOptInfo *rel);
static List *get_useful_ecs_for_relation(PlannerInfo *root, RelOptInfo *rel);
static void add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
Path *epq_path);
static void add_foreign_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *grouped_rel,
GroupPathExtraData *extra);
static void add_foreign_ordered_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *ordered_rel);
static void add_foreign_final_paths(PlannerInfo *root,
RelOptInfo *input_rel,
RelOptInfo *final_rel,
FinalPathExtraData *extra);
static void apply_server_options(PgFdwRelationInfo *fpinfo);
static void apply_table_options(PgFdwRelationInfo *fpinfo);
static void merge_fdw_options(PgFdwRelationInfo *fpinfo,
const PgFdwRelationInfo *fpinfo_o,
const PgFdwRelationInfo *fpinfo_i);
/*
* Foreign-data wrapper handler function: return a struct with pointers
* to my callback routines.
*/
Datum
postgres_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *routine = makeNode(FdwRoutine);
/* Functions for scanning foreign tables */
routine->GetForeignRelSize = postgresGetForeignRelSize;
routine->GetForeignPaths = postgresGetForeignPaths;
routine->GetForeignPlan = postgresGetForeignPlan;
routine->BeginForeignScan = postgresBeginForeignScan;
routine->IterateForeignScan = postgresIterateForeignScan;
routine->ReScanForeignScan = postgresReScanForeignScan;
routine->EndForeignScan = postgresEndForeignScan;
/* Functions for updating foreign tables */
routine->AddForeignUpdateTargets = postgresAddForeignUpdateTargets;
routine->PlanForeignModify = postgresPlanForeignModify;
routine->BeginForeignModify = postgresBeginForeignModify;
routine->ExecForeignInsert = postgresExecForeignInsert;
routine->ExecForeignUpdate = postgresExecForeignUpdate;
routine->ExecForeignDelete = postgresExecForeignDelete;
routine->EndForeignModify = postgresEndForeignModify;
routine->BeginForeignInsert = postgresBeginForeignInsert;
routine->EndForeignInsert = postgresEndForeignInsert;
routine->IsForeignRelUpdatable = postgresIsForeignRelUpdatable;
routine->PlanDirectModify = postgresPlanDirectModify;
routine->BeginDirectModify = postgresBeginDirectModify;
routine->IterateDirectModify = postgresIterateDirectModify;
routine->EndDirectModify = postgresEndDirectModify;
/* Function for EvalPlanQual rechecks */
routine->RecheckForeignScan = postgresRecheckForeignScan;
/* Support functions for EXPLAIN */
routine->ExplainForeignScan = postgresExplainForeignScan;
routine->ExplainForeignModify = postgresExplainForeignModify;
routine->ExplainDirectModify = postgresExplainDirectModify;
/* Support functions for ANALYZE */
routine->AnalyzeForeignTable = postgresAnalyzeForeignTable;
/* Support functions for IMPORT FOREIGN SCHEMA */
routine->ImportForeignSchema = postgresImportForeignSchema;
/* Support functions for join push-down */
routine->GetForeignJoinPaths = postgresGetForeignJoinPaths;
/* Support functions for upper relation push-down */
routine->GetForeignUpperPaths = postgresGetForeignUpperPaths;
PG_RETURN_POINTER(routine);
}
/*
* postgresGetForeignRelSize
* Estimate # of rows and width of the result of the scan
*
* We should consider the effect of all baserestrictinfo clauses here, but
* not any join clauses.
*/
static void
postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo;
ListCell *lc;
RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
const char *namespace;
const char *relname;
const char *refname;
/*
* We use PgFdwRelationInfo to pass various information to subsequent
* functions.
*/
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
baserel->fdw_private = (void *) fpinfo;
/* Base foreign tables need to be pushed down always. */
fpinfo->pushdown_safe = true;
/* Look up foreign-table catalog info. */
fpinfo->table = GetForeignTable(foreigntableid);
fpinfo->server = GetForeignServer(fpinfo->table->serverid);
/*
* Extract user-settable option values. Note that per-table setting of
* use_remote_estimate overrides per-server setting.
*/
fpinfo->use_remote_estimate = false;
fpinfo->fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
fpinfo->fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
fpinfo->shippable_extensions = NIL;
fpinfo->fetch_size = 100;
apply_server_options(fpinfo);
apply_table_options(fpinfo);
/*
* If the table or the server is configured to use remote estimates,
* identify which user to do remote access as during planning. This
* should match what ExecCheckRTEPerms() does. If we fail due to lack of
* permissions, the query would have failed at runtime anyway.
*/
if (fpinfo->use_remote_estimate)
{
Oid userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
fpinfo->user = GetUserMapping(userid, fpinfo->server->serverid);
}
else
fpinfo->user = NULL;
/*
* Identify which baserestrictinfo clauses can be sent to the remote
* server and which can't.
*/
classifyConditions(root, baserel, baserel->baserestrictinfo,
&fpinfo->remote_conds, &fpinfo->local_conds);
/*
* Identify which attributes will need to be retrieved from the remote
* server. These include all attrs needed for joins or final output, plus
* all attrs used in the local_conds. (Note: if we end up using a
* parameterized scan, it's possible that some of the join clauses will be
* sent to the remote and thus we wouldn't really need to retrieve the
* columns used in them. Doesn't seem worth detecting that case though.)
*/
fpinfo->attrs_used = NULL;
pull_varattnos((Node *) baserel->reltarget->exprs, baserel->relid,
&fpinfo->attrs_used);
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&fpinfo->attrs_used);
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
baserel->relid,
JOIN_INNER,
NULL,
false);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction clauses, as well as the
* average row width. Otherwise, estimate using whatever statistics we
* have locally, in a way similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
/*
* Get cost/size estimates with help of remote server. Save the
* values in fpinfo so we don't need to do it again to generate the
* basic foreign path.
*/
estimate_path_cost_size(root, baserel, NIL, NIL, NULL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost, &fpinfo->total_cost);
/* Report estimated baserel size to planner. */
baserel->rows = fpinfo->rows;
baserel->reltarget->width = fpinfo->width;
}
else
{
/*
* If the foreign table has never been ANALYZEd, it will have relpages
* and reltuples equal to zero, which most likely has nothing to do
* with reality. We can't do a whole lot about that if we're not
* allowed to consult the remote server, but we can use a hack similar
* to plancat.c's treatment of empty relations: use a minimum size
* estimate of 10 pages, and divide by the column-datatype-based width
* estimate to get the corresponding number of tuples.
*/
if (baserel->pages == 0 && baserel->tuples == 0)
{
baserel->pages = 10;
baserel->tuples =
(10 * BLCKSZ) / (baserel->reltarget->width +
MAXALIGN(SizeofHeapTupleHeader));
}
/* Estimate baserel size as best we can with local statistics. */
set_baserel_size_estimates(root, baserel);
/* Fill in basically-bogus cost estimates for use later. */
estimate_path_cost_size(root, baserel, NIL, NIL, NULL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost, &fpinfo->total_cost);
}
/*
* Set the name of relation in fpinfo, while we are constructing it here.
* It will be used to build the string describing the join relation in
* EXPLAIN output. We can't know whether VERBOSE option is specified or
* not, so always schema-qualify the foreign table name.
*/
fpinfo->relation_name = makeStringInfo();
namespace = get_namespace_name(get_rel_namespace(foreigntableid));
relname = get_rel_name(foreigntableid);
refname = rte->eref->aliasname;
appendStringInfo(fpinfo->relation_name, "%s.%s",
quote_identifier(namespace),
quote_identifier(relname));
if (*refname && strcmp(refname, relname) != 0)
appendStringInfo(fpinfo->relation_name, " %s",
quote_identifier(rte->eref->aliasname));
/* No outer and inner relations. */
fpinfo->make_outerrel_subquery = false;
fpinfo->make_innerrel_subquery = false;
fpinfo->lower_subquery_rels = NULL;
/* Set the relation index. */
fpinfo->relation_index = baserel->relid;
}
/*
* get_useful_ecs_for_relation
* Determine which EquivalenceClasses might be involved in useful
* orderings of this relation.
*
* This function is in some respects a mirror image of the core function
* pathkeys_useful_for_merging: for a regular table, we know what indexes
* we have and want to test whether any of them are useful. For a foreign
* table, we don't know what indexes are present on the remote side but
* want to speculate about which ones we'd like to use if they existed.
*
* This function returns a list of potentially-useful equivalence classes,
* but it does not guarantee that an EquivalenceMember exists which contains
* Vars only from the given relation. For example, given ft1 JOIN t1 ON
* ft1.x + t1.x = 0, this function will say that the equivalence class
* containing ft1.x + t1.x is potentially useful. Supposing ft1 is remote and
* t1 is local (or on a different server), it will turn out that no useful
* ORDER BY clause can be generated. It's not our job to figure that out
* here; we're only interested in identifying relevant ECs.
*/
static List *
get_useful_ecs_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
List *useful_eclass_list = NIL;
ListCell *lc;
Relids relids;
/*
* First, consider whether any active EC is potentially useful for a merge
* join against this relation.
*/
if (rel->has_eclass_joins)
{
foreach(lc, root->eq_classes)
{
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc);
if (eclass_useful_for_merging(root, cur_ec, rel))
useful_eclass_list = lappend(useful_eclass_list, cur_ec);
}
}
/*
* Next, consider whether there are any non-EC derivable join clauses that
* are merge-joinable. If the joininfo list is empty, we can exit
* quickly.
*/
if (rel->joininfo == NIL)
return useful_eclass_list;
/* If this is a child rel, we must use the topmost parent rel to search. */
if (IS_OTHER_REL(rel))
{
Assert(!bms_is_empty(rel->top_parent_relids));
relids = rel->top_parent_relids;
}
else
relids = rel->relids;
/* Check each join clause in turn. */
foreach(lc, rel->joininfo)
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
/* Consider only mergejoinable clauses */
if (restrictinfo->mergeopfamilies == NIL)
continue;
/* Make sure we've got canonical ECs. */
update_mergeclause_eclasses(root, restrictinfo);
/*
* restrictinfo->mergeopfamilies != NIL is sufficient to guarantee
* that left_ec and right_ec will be initialized, per comments in
* distribute_qual_to_rels.
*
* We want to identify which side of this merge-joinable clause
* contains columns from the relation produced by this RelOptInfo. We
* test for overlap, not containment, because there could be extra
* relations on either side. For example, suppose we've got something
* like ((A JOIN B ON A.x = B.x) JOIN C ON A.y = C.y) LEFT JOIN D ON
* A.y = D.y. The input rel might be the joinrel between A and B, and
* we'll consider the join clause A.y = D.y. relids contains a
* relation not involved in the join class (B) and the equivalence
* class for the left-hand side of the clause contains a relation not
* involved in the input rel (C). Despite the fact that we have only
* overlap and not containment in either direction, A.y is potentially
* useful as a sort column.
*
* Note that it's even possible that relids overlaps neither side of
* the join clause. For example, consider A LEFT JOIN B ON A.x = B.x
* AND A.x = 1. The clause A.x = 1 will appear in B's joininfo list,
* but overlaps neither side of B. In that case, we just skip this
* join clause, since it doesn't suggest a useful sort order for this
* relation.
*/
if (bms_overlap(relids, restrictinfo->right_ec->ec_relids))
useful_eclass_list = list_append_unique_ptr(useful_eclass_list,
restrictinfo->right_ec);
else if (bms_overlap(relids, restrictinfo->left_ec->ec_relids))
useful_eclass_list = list_append_unique_ptr(useful_eclass_list,
restrictinfo->left_ec);
}
return useful_eclass_list;
}
/*
* get_useful_pathkeys_for_relation
* Determine which orderings of a relation might be useful.
*
* Getting data in sorted order can be useful either because the requested
* order matches the final output ordering for the overall query we're
* planning, or because it enables an efficient merge join. Here, we try
* to figure out which pathkeys to consider.
*/
static List *
get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
List *useful_pathkeys_list = NIL;
List *useful_eclass_list;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) rel->fdw_private;
EquivalenceClass *query_ec = NULL;
ListCell *lc;
/*
* Pushing the query_pathkeys to the remote server is always worth
* considering, because it might let us avoid a local sort.
*/
fpinfo->qp_is_pushdown_safe = false;
if (root->query_pathkeys)
{
bool query_pathkeys_ok = true;
foreach(lc, root->query_pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc);
EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
Expr *em_expr;
/*
* The planner and executor don't have any clever strategy for
* taking data sorted by a prefix of the query's pathkeys and
* getting it to be sorted by all of those pathkeys. We'll just
* end up resorting the entire data set. So, unless we can push
* down all of the query pathkeys, forget it.
*
* is_foreign_expr would detect volatile expressions as well, but
* checking ec_has_volatile here saves some cycles.
*/
if (pathkey_ec->ec_has_volatile ||
!(em_expr = find_em_expr_for_rel(pathkey_ec, rel)) ||
!is_foreign_expr(root, rel, em_expr))
{
query_pathkeys_ok = false;
break;
}
}
if (query_pathkeys_ok)
{
useful_pathkeys_list = list_make1(list_copy(root->query_pathkeys));
fpinfo->qp_is_pushdown_safe = true;
}
}
/*
* Even if we're not using remote estimates, having the remote side do the
* sort generally won't be any worse than doing it locally, and it might
* be much better if the remote side can generate data in the right order
* without needing a sort at all. However, what we're going to do next is
* try to generate pathkeys that seem promising for possible merge joins,
* and that's more speculative. A wrong choice might hurt quite a bit, so
* bail out if we can't use remote estimates.
*/
if (!fpinfo->use_remote_estimate)
return useful_pathkeys_list;
/* Get the list of interesting EquivalenceClasses. */
useful_eclass_list = get_useful_ecs_for_relation(root, rel);
/* Extract unique EC for query, if any, so we don't consider it again. */
if (list_length(root->query_pathkeys) == 1)
{
PathKey *query_pathkey = linitial(root->query_pathkeys);
query_ec = query_pathkey->pk_eclass;
}
/*
* As a heuristic, the only pathkeys we consider here are those of length
* one. It's surely possible to consider more, but since each one we
* choose to consider will generate a round-trip to the remote side, we
* need to be a bit cautious here. It would sure be nice to have a local
* cache of information about remote index definitions...
*/
foreach(lc, useful_eclass_list)
{
EquivalenceClass *cur_ec = lfirst(lc);
Expr *em_expr;
PathKey *pathkey;
/* If redundant with what we did above, skip it. */
if (cur_ec == query_ec)
continue;
/* If no pushable expression for this rel, skip it. */
em_expr = find_em_expr_for_rel(cur_ec, rel);
if (em_expr == NULL || !is_foreign_expr(root, rel, em_expr))
continue;
/* Looks like we can generate a pathkey, so let's do it. */
pathkey = make_canonical_pathkey(root, cur_ec,
linitial_oid(cur_ec->ec_opfamilies),
BTLessStrategyNumber,
false);
useful_pathkeys_list = lappend(useful_pathkeys_list,
list_make1(pathkey));
}
return useful_pathkeys_list;
}
/*
* postgresGetForeignPaths
* Create possible scan paths for a scan on the foreign table
*/
static void
postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
ForeignPath *path;
List *ppi_list;
ListCell *lc;
/*
* Create simplest ForeignScan path node and add it to baserel. This path
* corresponds to SeqScan path of regular tables (though depending on what
* baserestrict conditions we were able to send to remote, there might
* actually be an indexscan happening there). We already did all the work
* to estimate cost and size of this path.
*
* Although this path uses no join clauses, it could still have required
* parameterization due to LATERAL refs in its tlist.
*/
path = create_foreignscan_path(root, baserel,
NULL, /* default pathtarget */
fpinfo->rows,
fpinfo->startup_cost,
fpinfo->total_cost,
NIL, /* no pathkeys */
baserel->lateral_relids,
NULL, /* no extra plan */
NIL); /* no fdw_private list */
add_path(baserel, (Path *) path);
/* Add paths with pathkeys */
add_paths_with_pathkeys_for_rel(root, baserel, NULL);
/*
* If we're not using remote estimates, stop here. We have no way to
* estimate whether any join clauses would be worth sending across, so
* don't bother building parameterized paths.
*/
if (!fpinfo->use_remote_estimate)
return;
/*
* Thumb through all join clauses for the rel to identify which outer
* relations could supply one or more safe-to-send-to-remote join clauses.
* We'll build a parameterized path for each such outer relation.
*
* It's convenient to manage this by representing each candidate outer
* relation by the ParamPathInfo node for it. We can then use the
* ppi_clauses list in the ParamPathInfo node directly as a list of the
* interesting join clauses for that rel. This takes care of the
* possibility that there are multiple safe join clauses for such a rel,
* and also ensures that we account for unsafe join clauses that we'll
* still have to enforce locally (since the parameterized-path machinery
* insists that we handle all movable clauses).
*/
ppi_list = NIL;
foreach(lc, baserel->joininfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Relids required_outer;
ParamPathInfo *param_info;
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel))
continue;
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause))
continue;
/* Calculate required outer rels for the resulting path */
required_outer = bms_union(rinfo->clause_relids,
baserel->lateral_relids);
/* We do not want the foreign rel itself listed in required_outer */
required_outer = bms_del_member(required_outer, baserel->relid);
/*
* required_outer probably can't be empty here, but if it were, we
* couldn't make a parameterized path.
*/
if (bms_is_empty(required_outer))
continue;
/* Get the ParamPathInfo */
param_info = get_baserel_parampathinfo(root, baserel,
required_outer);
Assert(param_info != NULL);
/*
* Add it to list unless we already have it. Testing pointer equality
* is OK since get_baserel_parampathinfo won't make duplicates.
*/
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/*
* The above scan examined only "generic" join clauses, not those that
* were absorbed into EquivalenceClauses. See if we can make anything out
* of EquivalenceClauses.
*/
if (baserel->has_eclass_joins)
{
/*
* We repeatedly scan the eclass list looking for column references
* (or expressions) belonging to the foreign rel. Each time we find
* one, we generate a list of equivalence joinclauses for it, and then
* see if any are safe to send to the remote. Repeat till there are
* no more candidate EC members.
*/
ec_member_foreign_arg arg;
arg.already_used = NIL;
for (;;)
{
List *clauses;
/* Make clauses, skipping any that join to lateral_referencers */
arg.current = NULL;
clauses = generate_implied_equalities_for_column(root,
baserel,
ec_member_matches_foreign,
(void *) &arg,
baserel->lateral_referencers);
/* Done if there are no more expressions in the foreign rel */
if (arg.current == NULL)
{
Assert(clauses == NIL);
break;
}
/* Scan the extracted join clauses */
foreach(lc, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Relids required_outer;
ParamPathInfo *param_info;
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel))
continue;
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause))
continue;
/* Calculate required outer rels for the resulting path */
required_outer = bms_union(rinfo->clause_relids,
baserel->lateral_relids);
required_outer = bms_del_member(required_outer, baserel->relid);
if (bms_is_empty(required_outer))
continue;
/* Get the ParamPathInfo */
param_info = get_baserel_parampathinfo(root, baserel,
required_outer);
Assert(param_info != NULL);
/* Add it to list unless we already have it */
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/* Try again, now ignoring the expression we found this time */
arg.already_used = lappend(arg.already_used, arg.current);
}
}
/*
* Now build a path for each useful outer relation.
*/
foreach(lc, ppi_list)
{
ParamPathInfo *param_info = (ParamPathInfo *) lfirst(lc);
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Get a cost estimate from the remote */
estimate_path_cost_size(root, baserel,
param_info->ppi_clauses, NIL, NULL,
&rows, &width,
&startup_cost, &total_cost);
/*
* ppi_rows currently won't get looked at by anything, but still we
* may as well ensure that it matches our idea of the rowcount.
*/
param_info->ppi_rows = rows;
/* Make the path */
path = create_foreignscan_path(root, baserel,
NULL, /* default pathtarget */
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
param_info->ppi_req_outer,
NULL,
NIL); /* no fdw_private list */
add_path(baserel, (Path *) path);
}
}
/*
* postgresGetForeignPlan
* Create ForeignScan plan node which implements selected best path
*/
static ForeignScan *
postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *foreignrel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses,
Plan *outer_plan)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
Index scan_relid;
List *fdw_private;
List *remote_exprs = NIL;
List *local_exprs = NIL;
List *params_list = NIL;
List *fdw_scan_tlist = NIL;
List *fdw_recheck_quals = NIL;
List *retrieved_attrs;
StringInfoData sql;
bool has_final_sort = false;
bool has_limit = false;
ListCell *lc;
/*
* Get FDW private data created by postgresGetForeignUpperPaths(), if any.
*/
if (best_path->fdw_private)
{
has_final_sort = intVal(list_nth(best_path->fdw_private,
FdwPathPrivateHasFinalSort));
has_limit = intVal(list_nth(best_path->fdw_private,
FdwPathPrivateHasLimit));
}
if (IS_SIMPLE_REL(foreignrel))
{
/*
* For base relations, set scan_relid as the relid of the relation.
*/
scan_relid = foreignrel->relid;
/*
* In a base-relation scan, we must apply the given scan_clauses.
*
* Separate the scan_clauses into those that can be executed remotely
* and those that can't. baserestrictinfo clauses that were
* previously determined to be safe or unsafe by classifyConditions
* are found in fpinfo->remote_conds and fpinfo->local_conds. Anything
* else in the scan_clauses list will be a join clause, which we have
* to check for remote-safety.
*
* Note: the join clauses we see here should be the exact same ones
* previously examined by postgresGetForeignPaths. Possibly it'd be
* worth passing forward the classification work done then, rather
* than repeating it here.
*
* This code must match "extract_actual_clauses(scan_clauses, false)"
* except for the additional decision about remote versus local
* execution.
*/
foreach(lc, scan_clauses)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
/* Ignore any pseudoconstants, they're dealt with elsewhere */
if (rinfo->pseudoconstant)
continue;
if (list_member_ptr(fpinfo->remote_conds, rinfo))
remote_exprs = lappend(remote_exprs, rinfo->clause);
else if (list_member_ptr(fpinfo->local_conds, rinfo))
local_exprs = lappend(local_exprs, rinfo->clause);
else if (is_foreign_expr(root, foreignrel, rinfo->clause))
remote_exprs = lappend(remote_exprs, rinfo->clause);
else
local_exprs = lappend(local_exprs, rinfo->clause);
}
/*
* For a base-relation scan, we have to support EPQ recheck, which
* should recheck all the remote quals.
*/
fdw_recheck_quals = remote_exprs;
}
else
{
/*
* Join relation or upper relation - set scan_relid to 0.
*/
scan_relid = 0;
/*
* For a join rel, baserestrictinfo is NIL and we are not considering
* parameterization right now, so there should be no scan_clauses for
* a joinrel or an upper rel either.
*/
Assert(!scan_clauses);
/*
* Instead we get the conditions to apply from the fdw_private
* structure.
*/
remote_exprs = extract_actual_clauses(fpinfo->remote_conds, false);
local_exprs = extract_actual_clauses(fpinfo->local_conds, false);
/*
* We leave fdw_recheck_quals empty in this case, since we never need
* to apply EPQ recheck clauses. In the case of a joinrel, EPQ
* recheck is handled elsewhere --- see postgresGetForeignJoinPaths().
* If we're planning an upperrel (ie, remote grouping or aggregation)
* then there's no EPQ to do because SELECT FOR UPDATE wouldn't be
* allowed, and indeed we *can't* put the remote clauses into
* fdw_recheck_quals because the unaggregated Vars won't be available
* locally.
*/
/* Build the list of columns to be fetched from the foreign server. */
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
/*
* Ensure that the outer plan produces a tuple whose descriptor
* matches our scan tuple slot. Also, remove the local conditions
* from outer plan's quals, lest they be evaluated twice, once by the
* local plan and once by the scan.
*/
if (outer_plan)
{
ListCell *lc;
/*
* Right now, we only consider grouping and aggregation beyond
* joins. Queries involving aggregates or grouping do not require
* EPQ mechanism, hence should not have an outer plan here.
*/
Assert(!IS_UPPER_REL(foreignrel));
/*
* First, update the plan's qual list if possible. In some cases
* the quals might be enforced below the topmost plan level, in
* which case we'll fail to remove them; it's not worth working
* harder than this.
*/
foreach(lc, local_exprs)
{
Node *qual = lfirst(lc);
outer_plan->qual = list_delete(outer_plan->qual, qual);
/*
* For an inner join the local conditions of foreign scan plan
* can be part of the joinquals as well. (They might also be
* in the mergequals or hashquals, but we can't touch those
* without breaking the plan.)
*/
if (IsA(outer_plan, NestLoop) ||
IsA(outer_plan, MergeJoin) ||
IsA(outer_plan, HashJoin))
{
Join *join_plan = (Join *) outer_plan;
if (join_plan->jointype == JOIN_INNER)
join_plan->joinqual = list_delete(join_plan->joinqual,
qual);
}
}
/*
* Now fix the subplan's tlist --- this might result in inserting
* a Result node atop the plan tree.
*/
outer_plan = change_plan_targetlist(outer_plan, fdw_scan_tlist,
best_path->path.parallel_safe);
}
}
/*
* Build the query string to be sent for execution, and identify
* expressions to be sent as parameters.
*/
initStringInfo(&sql);
deparseSelectStmtForRel(&sql, root, foreignrel, fdw_scan_tlist,
remote_exprs, best_path->path.pathkeys,
has_final_sort, has_limit, false,
&retrieved_attrs, ¶ms_list);
/* Remember remote_exprs for possible use by postgresPlanDirectModify */
fpinfo->final_remote_exprs = remote_exprs;
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match order in enum FdwScanPrivateIndex.
*/
fdw_private = list_make3(makeString(sql.data),
retrieved_attrs,
makeInteger(fpinfo->fetch_size));
if (IS_JOIN_REL(foreignrel) || IS_UPPER_REL(foreignrel))
fdw_private = lappend(fdw_private,
makeString(fpinfo->relation_name->data));
/*
* Create the ForeignScan node for the given relation.
*
* Note that the remote parameter expressions are stored in the fdw_exprs
* field of the finished plan node; we can't keep them in private state
* because then they wouldn't be subject to later planner processing.
*/
return make_foreignscan(tlist,
local_exprs,
scan_relid,
params_list,
fdw_private,
fdw_scan_tlist,
fdw_recheck_quals,
outer_plan);
}
/*
* postgresBeginForeignScan
* Initiate an executor scan of a foreign PostgreSQL table.
*/
static void
postgresBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwScanState *fsstate;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
UserMapping *user;
int rtindex;
int numParams;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
fsstate = (PgFdwScanState *) palloc0(sizeof(PgFdwScanState));
node->fdw_state = (void *) fsstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does. In case of a join or aggregate, use the
* lowest-numbered member RTE as a representative; we would get the same
* result from any.
*/
if (fsplan->scan.scanrelid > 0)
rtindex = fsplan->scan.scanrelid;
else
rtindex = bms_next_member(fsplan->fs_relids, -1);
rte = exec_rt_fetch(rtindex, estate);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
table = GetForeignTable(rte->relid);
user = GetUserMapping(userid, table->serverid);
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
fsstate->conn = GetConnection(user, false);
/* Assign a unique ID for my cursor */
fsstate->cursor_number = GetCursorNumber(fsstate->conn);
fsstate->cursor_exists = false;
/* Get private info created by planner functions. */
fsstate->query = strVal(list_nth(fsplan->fdw_private,
FdwScanPrivateSelectSql));
fsstate->retrieved_attrs = (List *) list_nth(fsplan->fdw_private,
FdwScanPrivateRetrievedAttrs);
fsstate->fetch_size = intVal(list_nth(fsplan->fdw_private,
FdwScanPrivateFetchSize));
/* Create contexts for batches of tuples and per-tuple temp workspace. */
fsstate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw tuple data",
ALLOCSET_DEFAULT_SIZES);
fsstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/*
* Get info we'll need for converting data fetched from the foreign server
* into local representation and error reporting during that process.
*/
if (fsplan->scan.scanrelid > 0)
{
fsstate->rel = node->ss.ss_currentRelation;
fsstate->tupdesc = RelationGetDescr(fsstate->rel);
}
else
{
fsstate->rel = NULL;
fsstate->tupdesc = node->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
}
fsstate->attinmeta = TupleDescGetAttInMetadata(fsstate->tupdesc);
/*
* Prepare for processing of parameters used in remote query, if any.
*/
numParams = list_length(fsplan->fdw_exprs);
fsstate->numParams = numParams;
if (numParams > 0)
prepare_query_params((PlanState *) node,
fsplan->fdw_exprs,
numParams,
&fsstate->param_flinfo,
&fsstate->param_exprs,
&fsstate->param_values);
}
/*
* postgresIterateForeignScan
* Retrieve next row from the result set, or clear tuple slot to indicate
* EOF.
*/
static TupleTableSlot *
postgresIterateForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
/*
* If this is the first call after Begin or ReScan, we need to create the
* cursor on the remote side.
*/
if (!fsstate->cursor_exists)
create_cursor(node);
/*
* Get some more tuples, if we've run out.
*/
if (fsstate->next_tuple >= fsstate->num_tuples)
{
/* No point in another fetch if we already detected EOF, though. */
if (!fsstate->eof_reached)
fetch_more_data(node);
/* If we didn't get any tuples, must be end of data. */
if (fsstate->next_tuple >= fsstate->num_tuples)
return ExecClearTuple(slot);
}
/*
* Return the next tuple.
*/
ExecStoreHeapTuple(fsstate->tuples[fsstate->next_tuple++],
slot,
false);
return slot;
}
/*
* postgresReScanForeignScan
* Restart the scan.
*/
static void
postgresReScanForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
char sql[64];
PGresult *res;
/* If we haven't created the cursor yet, nothing to do. */
if (!fsstate->cursor_exists)
return;
/*
* If any internal parameters affecting this node have changed, we'd
* better destroy and recreate the cursor. Otherwise, rewinding it should
* be good enough. If we've only fetched zero or one batch, we needn't
* even rewind the cursor, just rescan what we have.
*/
if (node->ss.ps.chgParam != NULL)
{
fsstate->cursor_exists = false;
snprintf(sql, sizeof(sql), "CLOSE c%u",
fsstate->cursor_number);
}
else if (fsstate->fetch_ct_2 > 1)
{
snprintf(sql, sizeof(sql), "MOVE BACKWARD ALL IN c%u",
fsstate->cursor_number);
}
else
{
/* Easy: just rescan what we already have in memory, if anything */
fsstate->next_tuple = 0;
return;
}
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_exec_query(fsstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fsstate->conn, true, sql);
PQclear(res);
/* Now force a fresh FETCH. */
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
}
/*
* postgresEndForeignScan
* Finish scanning foreign table and dispose objects used for this scan
*/
static void
postgresEndForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
/* if fsstate is NULL, we are in EXPLAIN; nothing to do */
if (fsstate == NULL)
return;
/* Close the cursor if open, to prevent accumulation of cursors */
if (fsstate->cursor_exists)
close_cursor(fsstate->conn, fsstate->cursor_number);
/* Release remote connection */
ReleaseConnection(fsstate->conn);
fsstate->conn = NULL;
/* MemoryContexts will be deleted automatically. */
}
/*
* postgresAddForeignUpdateTargets
* Add resjunk column(s) needed for update/delete on a foreign table
*/
static void
postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation)
{
Var *var;
const char *attrname;
TargetEntry *tle;
/*
* In postgres_fdw, what we need is the ctid, same as for a regular table.
*/
/* Make a Var representing the desired value */
var = makeVar(parsetree->resultRelation,
SelfItemPointerAttributeNumber,
TIDOID,
-1,
InvalidOid,
0);
/* Wrap it in a resjunk TLE with the right name ... */
attrname = "ctid";
tle = makeTargetEntry((Expr *) var,
list_length(parsetree->targetList) + 1,
pstrdup(attrname),
true);
/* ... and add it to the query's targetlist */
parsetree->targetList = lappend(parsetree->targetList, tle);
}
/*
* postgresPlanForeignModify
* Plan an insert/update/delete operation on a foreign table
*/
static List *
postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index)
{
CmdType operation = plan->operation;
RangeTblEntry *rte = planner_rt_fetch(resultRelation, root);
Relation rel;
StringInfoData sql;
List *targetAttrs = NIL;
List *withCheckOptionList = NIL;
List *returningList = NIL;
List *retrieved_attrs = NIL;
bool doNothing = false;
initStringInfo(&sql);
/*
* Core code already has some lock on each rel being planned, so we can
* use NoLock here.
*/
rel = table_open(rte->relid, NoLock);
/*
* In an INSERT, we transmit all columns that are defined in the foreign
* table. In an UPDATE, if there are BEFORE ROW UPDATE triggers on the
* foreign table, we transmit all columns like INSERT; else we transmit
* only columns that were explicitly targets of the UPDATE, so as to avoid
* unnecessary data transmission. (We can't do that for INSERT since we
* would miss sending default values for columns not listed in the source
* statement, and for UPDATE if there are BEFORE ROW UPDATE triggers since
* those triggers might change values for non-target columns, in which
* case we would miss sending changed values for those columns.)
*/
if (operation == CMD_INSERT ||
(operation == CMD_UPDATE &&
rel->trigdesc &&
rel->trigdesc->trig_update_before_row))
{
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
for (attnum = 1; attnum <= tupdesc->natts; attnum++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
if (!attr->attisdropped)
targetAttrs = lappend_int(targetAttrs, attnum);
}
}
else if (operation == CMD_UPDATE)
{
int col;
Bitmapset *allUpdatedCols = bms_union(rte->updatedCols, rte->extraUpdatedCols);
col = -1;
while ((col = bms_next_member(allUpdatedCols, col)) >= 0)
{
/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
AttrNumber attno = col + FirstLowInvalidHeapAttributeNumber;
if (attno <= InvalidAttrNumber) /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
targetAttrs = lappend_int(targetAttrs, attno);
}
}
/*
* Extract the relevant WITH CHECK OPTION list if any.
*/
if (plan->withCheckOptionLists)
withCheckOptionList = (List *) list_nth(plan->withCheckOptionLists,
subplan_index);
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists)
returningList = (List *) list_nth(plan->returningLists, subplan_index);
/*
* ON CONFLICT DO UPDATE and DO NOTHING case with inference specification
* should have already been rejected in the optimizer, as presently there
* is no way to recognize an arbiter index on a foreign table. Only DO
* NOTHING is supported without an inference specification.
*/
if (plan->onConflictAction == ONCONFLICT_NOTHING)
doNothing = true;
else if (plan->onConflictAction != ONCONFLICT_NONE)
elog(ERROR, "unexpected ON CONFLICT specification: %d",
(int) plan->onConflictAction);
/*
* Construct the SQL command string.
*/
switch (operation)
{
case CMD_INSERT:
deparseInsertSql(&sql, rte, resultRelation, rel,
targetAttrs, doNothing,
withCheckOptionList, returningList,
&retrieved_attrs);
break;
case CMD_UPDATE:
deparseUpdateSql(&sql, rte, resultRelation, rel,
targetAttrs,
withCheckOptionList, returningList,
&retrieved_attrs);
break;
case CMD_DELETE:
deparseDeleteSql(&sql, rte, resultRelation, rel,
returningList,
&retrieved_attrs);
break;
default:
elog(ERROR, "unexpected operation: %d", (int) operation);
break;
}
table_close(rel, NoLock);
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwModifyPrivateIndex, above.
*/
return list_make4(makeString(sql.data),
targetAttrs,
makeInteger((retrieved_attrs != NIL)),
retrieved_attrs);
}
/*
* postgresBeginForeignModify
* Begin an insert/update/delete operation on a foreign table
*/
static void
postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags)
{
PgFdwModifyState *fmstate;
char *query;
List *target_attrs;
bool has_returning;
List *retrieved_attrs;
RangeTblEntry *rte;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. resultRelInfo->ri_FdwState
* stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/* Deconstruct fdw_private data. */
query = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
target_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateTargetAttnums);
has_returning = intVal(list_nth(fdw_private,
FdwModifyPrivateHasReturning));
retrieved_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateRetrievedAttrs);
/* Find RTE. */
rte = exec_rt_fetch(resultRelInfo->ri_RangeTableIndex,
mtstate->ps.state);
/* Construct an execution state. */
fmstate = create_foreign_modify(mtstate->ps.state,
rte,
resultRelInfo,
mtstate->operation,
mtstate->mt_plans[subplan_index]->plan,
query,
target_attrs,
has_returning,
retrieved_attrs);
resultRelInfo->ri_FdwState = fmstate;
}
/*
* postgresExecForeignInsert
* Insert one row into a foreign table
*/
static TupleTableSlot *
postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
TupleTableSlot *rslot;
/*
* If the fmstate has aux_fmstate set, use the aux_fmstate (see
* postgresBeginForeignInsert())
*/
if (fmstate->aux_fmstate)
resultRelInfo->ri_FdwState = fmstate->aux_fmstate;
rslot = execute_foreign_modify(estate, resultRelInfo, CMD_INSERT,
slot, planSlot);
/* Revert that change */
if (fmstate->aux_fmstate)
resultRelInfo->ri_FdwState = fmstate;
return rslot;
}
/*
* postgresExecForeignUpdate
* Update one row in a foreign table
*/
static TupleTableSlot *
postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
return execute_foreign_modify(estate, resultRelInfo, CMD_UPDATE,
slot, planSlot);
}
/*
* postgresExecForeignDelete
* Delete one row from a foreign table
*/
static TupleTableSlot *
postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
return execute_foreign_modify(estate, resultRelInfo, CMD_DELETE,
slot, planSlot);
}
/*
* postgresEndForeignModify
* Finish an insert/update/delete operation on a foreign table
*/
static void
postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
/* If fmstate is NULL, we are in EXPLAIN; nothing to do */
if (fmstate == NULL)
return;
/* Destroy the execution state */
finish_foreign_modify(fmstate);
}
/*
* postgresBeginForeignInsert
* Begin an insert operation on a foreign table
*/
static void
postgresBeginForeignInsert(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate;
ModifyTable *plan = castNode(ModifyTable, mtstate->ps.plan);
EState *estate = mtstate->ps.state;
Index resultRelation = resultRelInfo->ri_RangeTableIndex;
Relation rel = resultRelInfo->ri_RelationDesc;
RangeTblEntry *rte;
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
StringInfoData sql;
List *targetAttrs = NIL;
List *retrieved_attrs = NIL;
bool doNothing = false;
/*
* If the foreign table we are about to insert routed rows into is also an
* UPDATE subplan result rel that will be updated later, proceeding with
* the INSERT will result in the later UPDATE incorrectly modifying those
* routed rows, so prevent the INSERT --- it would be nice if we could
* handle this case; but for now, throw an error for safety.
*/
if (plan && plan->operation == CMD_UPDATE &&
(resultRelInfo->ri_usesFdwDirectModify ||
resultRelInfo->ri_FdwState) &&
resultRelInfo > mtstate->resultRelInfo + mtstate->mt_whichplan)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("cannot route tuples into foreign table to be updated \"%s\"",
RelationGetRelationName(rel))));
initStringInfo(&sql);
/* We transmit all columns that are defined in the foreign table. */
for (attnum = 1; attnum <= tupdesc->natts; attnum++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
if (!attr->attisdropped)
targetAttrs = lappend_int(targetAttrs, attnum);
}
/* Check if we add the ON CONFLICT clause to the remote query. */
if (plan)
{
OnConflictAction onConflictAction = plan->onConflictAction;
/* We only support DO NOTHING without an inference specification. */
if (onConflictAction == ONCONFLICT_NOTHING)
doNothing = true;
else if (onConflictAction != ONCONFLICT_NONE)
elog(ERROR, "unexpected ON CONFLICT specification: %d",
(int) onConflictAction);
}
/*
* If the foreign table is a partition, we need to create a new RTE
* describing the foreign table for use by deparseInsertSql and
* create_foreign_modify() below, after first copying the parent's RTE and
* modifying some fields to describe the foreign partition to work on.
* However, if this is invoked by UPDATE, the existing RTE may already
* correspond to this partition if it is one of the UPDATE subplan target
* rels; in that case, we can just use the existing RTE as-is.
*/
rte = exec_rt_fetch(resultRelation, estate);
if (rte->relid != RelationGetRelid(rel))
{
rte = copyObject(rte);
rte->relid = RelationGetRelid(rel);
rte->relkind = RELKIND_FOREIGN_TABLE;
/*
* For UPDATE, we must use the RT index of the first subplan target
* rel's RTE, because the core code would have built expressions for
* the partition, such as RETURNING, using that RT index as varno of
* Vars contained in those expressions.
*/
if (plan && plan->operation == CMD_UPDATE &&
resultRelation == plan->rootRelation)
resultRelation = mtstate->resultRelInfo[0].ri_RangeTableIndex;
}
/* Construct the SQL command string. */
deparseInsertSql(&sql, rte, resultRelation, rel, targetAttrs, doNothing,
resultRelInfo->ri_WithCheckOptions,
resultRelInfo->ri_returningList,
&retrieved_attrs);
/* Construct an execution state. */
fmstate = create_foreign_modify(mtstate->ps.state,
rte,
resultRelInfo,
CMD_INSERT,
NULL,
sql.data,
targetAttrs,
retrieved_attrs != NIL,
retrieved_attrs);
/*
* If the given resultRelInfo already has PgFdwModifyState set, it means
* the foreign table is an UPDATE subplan result rel; in which case, store
* the resulting state into the aux_fmstate of the PgFdwModifyState.
*/
if (resultRelInfo->ri_FdwState)
{
Assert(plan && plan->operation == CMD_UPDATE);
Assert(resultRelInfo->ri_usesFdwDirectModify == false);
((PgFdwModifyState *) resultRelInfo->ri_FdwState)->aux_fmstate = fmstate;
}
else
resultRelInfo->ri_FdwState = fmstate;
}
/*
* postgresEndForeignInsert
* Finish an insert operation on a foreign table
*/
static void
postgresEndForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
Assert(fmstate != NULL);
/*
* If the fmstate has aux_fmstate set, get the aux_fmstate (see
* postgresBeginForeignInsert())
*/
if (fmstate->aux_fmstate)
fmstate = fmstate->aux_fmstate;
/* Destroy the execution state */
finish_foreign_modify(fmstate);
}
/*
* postgresIsForeignRelUpdatable
* Determine whether a foreign table supports INSERT, UPDATE and/or
* DELETE.
*/
static int
postgresIsForeignRelUpdatable(Relation rel)
{
bool updatable;
ForeignTable *table;
ForeignServer *server;
ListCell *lc;
/*
* By default, all postgres_fdw foreign tables are assumed updatable. This
* can be overridden by a per-server setting, which in turn can be
* overridden by a per-table setting.
*/
updatable = true;
table = GetForeignTable(RelationGetRelid(rel));
server = GetForeignServer(table->serverid);
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "updatable") == 0)
updatable = defGetBoolean(def);
}
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "updatable") == 0)
updatable = defGetBoolean(def);
}
/*
* Currently "updatable" means support for INSERT, UPDATE and DELETE.
*/
if (!updatable)
return 0;
/*
* Greenplum only supports INSERT, because UPDATE/DELETE SELECT requires
* the hidden column gp_segment_id and the other "ModifyTable mixes
* distributed and entry-only tables" issue.
*/
UserMapping *user = GetUserMapping(rel->rd_rel->relowner, table->serverid);
if (greenplumCheckIsGreenplum(user))
return (1 << CMD_INSERT);
else
return (1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE);
}
/*
* postgresRecheckForeignScan
* Execute a local join execution plan for a foreign join
*/
static bool
postgresRecheckForeignScan(ForeignScanState *node, TupleTableSlot *slot)
{
Index scanrelid = ((Scan *) node->ss.ps.plan)->scanrelid;
PlanState *outerPlan = outerPlanState(node);
TupleTableSlot *result;
/* For base foreign relations, it suffices to set fdw_recheck_quals */
if (scanrelid > 0)
return true;
Assert(outerPlan != NULL);
/* Execute a local join execution plan */
result = ExecProcNode(outerPlan);
if (TupIsNull(result))
return false;
/* Store result in the given slot */
ExecCopySlot(slot, result);
return true;
}
/*
* postgresPlanDirectModify
* Consider a direct foreign table modification
*
* Decide whether it is safe to modify a foreign table directly, and if so,
* rewrite subplan accordingly.
*/
static bool
postgresPlanDirectModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index)
{
CmdType operation = plan->operation;
Plan *subplan;
RelOptInfo *foreignrel;
RangeTblEntry *rte;
PgFdwRelationInfo *fpinfo;
Relation rel;
StringInfoData sql;
ForeignScan *fscan;
List *targetAttrs = NIL;
List *remote_exprs;
List *params_list = NIL;
List *returningList = NIL;
List *retrieved_attrs = NIL;
/*
* Decide whether it is safe to modify a foreign table directly.
*/
/*
* The table modification must be an UPDATE or DELETE.
*/
if (operation != CMD_UPDATE && operation != CMD_DELETE)
return false;
/*
* It's unsafe to modify a foreign table directly if there are any local
* joins needed.
*/
subplan = (Plan *) list_nth(plan->plans, subplan_index);
if (!IsA(subplan, ForeignScan))
return false;
fscan = (ForeignScan *) subplan;
/*
* It's unsafe to modify a foreign table directly if there are any quals
* that should be evaluated locally.
*/
if (subplan->qual != NIL)
return false;
/* Safe to fetch data about the target foreign rel */
if (fscan->scan.scanrelid == 0)
{
foreignrel = find_join_rel(root, fscan->fs_relids);
/* We should have a rel for this foreign join. */
Assert(foreignrel);
}
else
foreignrel = root->simple_rel_array[resultRelation];
rte = root->simple_rte_array[resultRelation];
fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
/*
* It's unsafe to update a foreign table directly, if any expressions to
* assign to the target columns are unsafe to evaluate remotely.
*/
if (operation == CMD_UPDATE)
{
int col;
/*
* We transmit only columns that were explicitly targets of the
* UPDATE, so as to avoid unnecessary data transmission.
*/
col = -1;
while ((col = bms_next_member(rte->updatedCols, col)) >= 0)
{
/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
AttrNumber attno = col + FirstLowInvalidHeapAttributeNumber;
TargetEntry *tle;
if (attno <= InvalidAttrNumber) /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
tle = get_tle_by_resno(subplan->targetlist, attno);
if (!tle)
elog(ERROR, "attribute number %d not found in subplan targetlist",
attno);
if (!is_foreign_expr(root, foreignrel, (Expr *) tle->expr))
return false;
targetAttrs = lappend_int(targetAttrs, attno);
}
}
/*
* Ok, rewrite subplan so as to modify the foreign table directly.
*/
initStringInfo(&sql);
/*
* Core code already has some lock on each rel being planned, so we can
* use NoLock here.
*/
rel = table_open(rte->relid, NoLock);
/*
* Recall the qual clauses that must be evaluated remotely. (These are
* bare clauses not RestrictInfos, but deparse.c's appendConditions()
* doesn't care.)
*/
remote_exprs = fpinfo->final_remote_exprs;
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists)
{
returningList = (List *) list_nth(plan->returningLists, subplan_index);
/*
* When performing an UPDATE/DELETE .. RETURNING on a join directly,
* we fetch from the foreign server any Vars specified in RETURNING
* that refer not only to the target relation but to non-target
* relations. So we'll deparse them into the RETURNING clause of the
* remote query; use a targetlist consisting of them instead, which
* will be adjusted to be new fdw_scan_tlist of the foreign-scan plan
* node below.
*/
if (fscan->scan.scanrelid == 0)
returningList = build_remote_returning(resultRelation, rel,
returningList);
}
/*
* Construct the SQL command string.
*/
switch (operation)
{
case CMD_UPDATE:
deparseDirectUpdateSql(&sql, root, resultRelation, rel,
foreignrel,
((Plan *) fscan)->targetlist,
targetAttrs,
remote_exprs, ¶ms_list,
returningList, &retrieved_attrs);
break;
case CMD_DELETE:
deparseDirectDeleteSql(&sql, root, resultRelation, rel,
foreignrel,
remote_exprs, ¶ms_list,
returningList, &retrieved_attrs);
break;
default:
elog(ERROR, "unexpected operation: %d", (int) operation);
break;
}
/*
* Update the operation info.
*/
fscan->operation = operation;
/*
* Update the fdw_exprs list that will be available to the executor.
*/
fscan->fdw_exprs = params_list;
/*
* Update the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwDirectModifyPrivateIndex, above.
*/
fscan->fdw_private = list_make4(makeString(sql.data),
makeInteger((retrieved_attrs != NIL)),
retrieved_attrs,
makeInteger(plan->canSetTag));
/*
* Update the foreign-join-related fields.
*/
if (fscan->scan.scanrelid == 0)
{
/* No need for the outer subplan. */
fscan->scan.plan.lefttree = NULL;
/* Build new fdw_scan_tlist if UPDATE/DELETE .. RETURNING. */
if (returningList)
rebuild_fdw_scan_tlist(fscan, returningList);
}
table_close(rel, NoLock);
return true;
}
/*
* postgresBeginDirectModify
* Prepare a direct foreign table modification
*/
static void
postgresBeginDirectModify(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwDirectModifyState *dmstate;
Index rtindex;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
UserMapping *user;
int numParams;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
dmstate = (PgFdwDirectModifyState *) palloc0(sizeof(PgFdwDirectModifyState));
node->fdw_state = (void *) dmstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
rtindex = estate->es_result_relation_info->ri_RangeTableIndex;
rte = exec_rt_fetch(rtindex, estate);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
if (fsplan->scan.scanrelid == 0)
dmstate->rel = ExecOpenScanRelation(estate, rtindex, eflags);
else
dmstate->rel = node->ss.ss_currentRelation;
table = GetForeignTable(RelationGetRelid(dmstate->rel));
user = GetUserMapping(userid, table->serverid);
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
dmstate->conn = GetConnection(user, false);
/* Update the foreign-join-related fields. */
if (fsplan->scan.scanrelid == 0)
{
/* Save info about foreign table. */
dmstate->resultRel = dmstate->rel;
/*
* Set dmstate->rel to NULL to teach get_returning_data() and
* make_tuple_from_result_row() that columns fetched from the remote
* server are described by fdw_scan_tlist of the foreign-scan plan
* node, not the tuple descriptor for the target relation.
*/
dmstate->rel = NULL;
}
/* Initialize state variable */
dmstate->num_tuples = -1; /* -1 means not set yet */
/* Get private info created by planner functions. */
dmstate->query = strVal(list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateUpdateSql));
dmstate->has_returning = intVal(list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateHasReturning));
dmstate->retrieved_attrs = (List *) list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateRetrievedAttrs);
dmstate->set_processed = intVal(list_nth(fsplan->fdw_private,
FdwDirectModifyPrivateSetProcessed));
/* Create context for per-tuple temp workspace. */
dmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/* Prepare for input conversion of RETURNING results. */
if (dmstate->has_returning)
{
TupleDesc tupdesc;
if (fsplan->scan.scanrelid == 0)
tupdesc = node->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
else
tupdesc = RelationGetDescr(dmstate->rel);
dmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
/*
* When performing an UPDATE/DELETE .. RETURNING on a join directly,
* initialize a filter to extract an updated/deleted tuple from a scan
* tuple.
*/
if (fsplan->scan.scanrelid == 0)
init_returning_filter(dmstate, fsplan->fdw_scan_tlist, rtindex);
}
/*
* Prepare for processing of parameters used in remote query, if any.
*/
numParams = list_length(fsplan->fdw_exprs);
dmstate->numParams = numParams;
if (numParams > 0)
prepare_query_params((PlanState *) node,
fsplan->fdw_exprs,
numParams,
&dmstate->param_flinfo,
&dmstate->param_exprs,
&dmstate->param_values);
}
/*
* postgresIterateDirectModify
* Execute a direct foreign table modification
*/
static TupleTableSlot *
postgresIterateDirectModify(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
EState *estate = node->ss.ps.state;
ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
/*
* If this is the first call after Begin, execute the statement.
*/
if (dmstate->num_tuples == -1)
execute_dml_stmt(node);
/*
* If the local query doesn't specify RETURNING, just clear tuple slot.
*/
if (!resultRelInfo->ri_projectReturning)
{
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
Instrumentation *instr = node->ss.ps.instrument;
Assert(!dmstate->has_returning);
/* Increment the command es_processed count if necessary. */
if (dmstate->set_processed)
estate->es_processed += dmstate->num_tuples;
/* Increment the tuple count for EXPLAIN ANALYZE if necessary. */
if (instr)
instr->tuplecount += dmstate->num_tuples;
return ExecClearTuple(slot);
}
/*
* Get the next RETURNING tuple.
*/
return get_returning_data(node);
}
/*
* postgresEndDirectModify
* Finish a direct foreign table modification
*/
static void
postgresEndDirectModify(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
/* if dmstate is NULL, we are in EXPLAIN; nothing to do */
if (dmstate == NULL)
return;
/* Release PGresult */
if (dmstate->result)
PQclear(dmstate->result);
/* Release remote connection */
ReleaseConnection(dmstate->conn);
dmstate->conn = NULL;
/* MemoryContext will be deleted automatically. */
}
/*
* postgresExplainForeignScan
* Produce extra output for EXPLAIN of a ForeignScan on a foreign table
*/
static void
postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
List *fdw_private;
char *sql;
char *relations;
fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
/*
* Add names of relation handled by the foreign scan when the scan is a
* join
*/
if (list_length(fdw_private) > FdwScanPrivateRelations)
{
relations = strVal(list_nth(fdw_private, FdwScanPrivateRelations));
ExplainPropertyText("Relations", relations, es);
}
/*
* Add remote query, when VERBOSE option is specified.
*/
if (es->verbose)
{
sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainForeignModify
* Produce extra output for EXPLAIN of a ModifyTable on a foreign table
*/
static void
postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es)
{
if (es->verbose)
{
char *sql = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainDirectModify
* Produce extra output for EXPLAIN of a ForeignScan that modifies a
* foreign table directly
*/
static void
postgresExplainDirectModify(ForeignScanState *node, ExplainState *es)
{
List *fdw_private;
char *sql;
if (es->verbose)
{
fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
sql = strVal(list_nth(fdw_private, FdwDirectModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* estimate_path_cost_size
* Get cost and size estimates for a foreign scan on given foreign relation
* either a base relation or a join between foreign relations or an upper
* relation containing foreign relations.
*
* param_join_conds are the parameterization clauses with outer relations.
* pathkeys specify the expected sort order if any for given path being costed.
* fpextra specifies additional post-scan/join-processing steps such as the
* final sort and the LIMIT restriction.
*
* The function returns the cost and size estimates in p_rows, p_width,
* p_startup_cost and p_total_cost variables.
*/
static void
estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *foreignrel,
List *param_join_conds,
List *pathkeys,
PgFdwPathExtraData *fpextra,
double *p_rows, int *p_width,
Cost *p_startup_cost, Cost *p_total_cost)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) foreignrel->fdw_private;
double rows;
double retrieved_rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Make sure the core code has set up the relation's reltarget */
Assert(foreignrel->reltarget);
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction+join clauses. Otherwise,
* estimate rows using whatever statistics we have locally, in a way
* similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
List *remote_param_join_conds;
List *local_param_join_conds;
StringInfoData sql;
PGconn *conn;
Selectivity local_sel;
QualCost local_cost;
List *fdw_scan_tlist = NIL;
List *remote_conds;
/* Required only to be passed to deparseSelectStmtForRel */
List *retrieved_attrs;
/*
* param_join_conds might contain both clauses that are safe to send
* across, and clauses that aren't.
*/
classifyConditions(root, foreignrel, param_join_conds,
&remote_param_join_conds, &local_param_join_conds);
/* Build the list of columns to be fetched from the foreign server. */
if (IS_JOIN_REL(foreignrel) || IS_UPPER_REL(foreignrel))
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
else
fdw_scan_tlist = NIL;
/*
* The complete list of remote conditions includes everything from
* baserestrictinfo plus any extra join_conds relevant to this
* particular path.
*/
remote_conds = list_concat(list_copy(remote_param_join_conds),
fpinfo->remote_conds);
/*
* Construct EXPLAIN query including the desired SELECT, FROM, and
* WHERE clauses. Params and other-relation Vars are replaced by dummy
* values, so don't request params_list.
*/
initStringInfo(&sql);
appendStringInfoString(&sql, "EXPLAIN ");
deparseSelectStmtForRel(&sql, root, foreignrel, fdw_scan_tlist,
remote_conds, pathkeys,
fpextra ? fpextra->has_final_sort : false,
fpextra ? fpextra->has_limit : false,
false, &retrieved_attrs, NULL);
/* Get the remote estimate */
conn = GetConnection(fpinfo->user, false);
get_remote_estimate(sql.data, conn, &rows, &width,
&startup_cost, &total_cost);
ReleaseConnection(conn);
retrieved_rows = rows;
/* Factor in the selectivity of the locally-checked quals */
local_sel = clauselist_selectivity(root,
local_param_join_conds,
foreignrel->relid,
JOIN_INNER,
NULL,
false);
local_sel *= fpinfo->local_conds_sel;
rows = clamp_row_est(rows * local_sel);
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
total_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
cost_qual_eval(&local_cost, local_param_join_conds, root);
startup_cost += local_cost.startup;
total_cost += local_cost.per_tuple * retrieved_rows;
/*
* Add in tlist eval cost for each output row. In case of an
* aggregate, some of the tlist expressions such as grouping
* expressions will be evaluated remotely, so adjust the costs.
*/
startup_cost += foreignrel->reltarget->cost.startup;
total_cost += foreignrel->reltarget->cost.startup;
total_cost += foreignrel->reltarget->cost.per_tuple * rows;
if (IS_UPPER_REL(foreignrel))
{
QualCost tlist_cost;
cost_qual_eval(&tlist_cost, fdw_scan_tlist, root);
startup_cost -= tlist_cost.startup;
total_cost -= tlist_cost.startup;
total_cost -= tlist_cost.per_tuple * rows;
}
}
else
{
Cost run_cost = 0;
/*
* We don't support join conditions in this mode (hence, no
* parameterized paths can be made).
*/
Assert(param_join_conds == NIL);
/*
* We will come here again and again with different set of pathkeys or
* additional post-scan/join-processing steps that caller wants to
* cost. We don't need to calculate the cost/size estimates for the
* underlying scan, join, or grouping each time. Instead, use those
* estimates if we have cached them already.
*/
if (fpinfo->rel_startup_cost >= 0 && fpinfo->rel_total_cost >= 0)
{
Assert(fpinfo->retrieved_rows >= 1);
rows = fpinfo->rows;
retrieved_rows = fpinfo->retrieved_rows;
width = fpinfo->width;
startup_cost = fpinfo->rel_startup_cost;
run_cost = fpinfo->rel_total_cost - fpinfo->rel_startup_cost;
/*
* If we estimate the costs of a foreign scan or a foreign join
* with additional post-scan/join-processing steps, the scan or
* join costs obtained from the cache wouldn't yet contain the
* eval costs for the final scan/join target, which would've been
* updated by apply_scanjoin_target_to_paths(); add the eval costs
* now.
*/
if (fpextra && !IS_UPPER_REL(foreignrel))
{
/* Shouldn't get here unless we have LIMIT */
Assert(fpextra->has_limit);
Assert(foreignrel->reloptkind == RELOPT_BASEREL ||
foreignrel->reloptkind == RELOPT_JOINREL);
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
}
else if (IS_JOIN_REL(foreignrel))
{
PgFdwRelationInfo *fpinfo_i;
PgFdwRelationInfo *fpinfo_o;
QualCost join_cost;
QualCost remote_conds_cost;
double nrows;
/* Use rows/width estimates made by the core code. */
rows = foreignrel->rows;
width = foreignrel->reltarget->width;
/* For join we expect inner and outer relations set */
Assert(fpinfo->innerrel && fpinfo->outerrel);
fpinfo_i = (PgFdwRelationInfo *) fpinfo->innerrel->fdw_private;
fpinfo_o = (PgFdwRelationInfo *) fpinfo->outerrel->fdw_private;
/* Estimate of number of rows in cross product */
nrows = fpinfo_i->rows * fpinfo_o->rows;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most nrow.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, nrows);
/*
* The cost of foreign join is estimated as cost of generating
* rows for the joining relations + cost for applying quals on the
* rows.
*/
/*
* Calculate the cost of clauses pushed down to the foreign server
*/
cost_qual_eval(&remote_conds_cost, fpinfo->remote_conds, root);
/* Calculate the cost of applying join clauses */
cost_qual_eval(&join_cost, fpinfo->joinclauses, root);
/*
* Startup cost includes startup cost of joining relations and the
* startup cost for join and other clauses. We do not include the
* startup cost specific to join strategy (e.g. setting up hash
* tables) since we do not know what strategy the foreign server
* is going to use.
*/
startup_cost = fpinfo_i->rel_startup_cost + fpinfo_o->rel_startup_cost;
startup_cost += join_cost.startup;
startup_cost += remote_conds_cost.startup;
startup_cost += fpinfo->local_conds_cost.startup;
/*
* Run time cost includes:
*
* 1. Run time cost (total_cost - startup_cost) of relations being
* joined
*
* 2. Run time cost of applying join clauses on the cross product
* of the joining relations.
*
* 3. Run time cost of applying pushed down other clauses on the
* result of join
*
* 4. Run time cost of applying nonpushable other clauses locally
* on the result fetched from the foreign server.
*/
run_cost = fpinfo_i->rel_total_cost - fpinfo_i->rel_startup_cost;
run_cost += fpinfo_o->rel_total_cost - fpinfo_o->rel_startup_cost;
run_cost += nrows * join_cost.per_tuple;
nrows = clamp_row_est(nrows * fpinfo->joinclause_sel);
run_cost += nrows * remote_conds_cost.per_tuple;
run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
/* Add in tlist eval cost for each output row */
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
else if (IS_UPPER_REL(foreignrel))
{
RelOptInfo *outerrel = fpinfo->outerrel;
PgFdwRelationInfo *ofpinfo;
AggClauseCosts aggcosts;
double input_rows;
int numGroupCols;
double numGroups = 1;
/* The upper relation should have its outer relation set */
Assert(outerrel);
/* and that outer relation should have its reltarget set */
Assert(outerrel->reltarget);
/*
* This cost model is mixture of costing done for sorted and
* hashed aggregates in cost_agg(). We are not sure which
* strategy will be considered at remote side, thus for
* simplicity, we put all startup related costs in startup_cost
* and all finalization and run cost are added in total_cost.
*/
ofpinfo = (PgFdwRelationInfo *) outerrel->fdw_private;
/* Get rows from input rel */
input_rows = ofpinfo->rows;
/* Collect statistics about aggregates for estimating costs. */
MemSet(&aggcosts, 0, sizeof(AggClauseCosts));
if (root->parse->hasAggs)
{
get_agg_clause_costs(root, (Node *) fpinfo->grouped_tlist,
AGGSPLIT_SIMPLE, &aggcosts);
/*
* The cost of aggregates in the HAVING qual will be the same
* for each child as it is for the parent, so there's no need
* to use a translated version of havingQual.
*/
get_agg_clause_costs(root, (Node *) root->parse->havingQual,
AGGSPLIT_SIMPLE, &aggcosts);
}
/* Get number of grouping columns and possible number of groups */
numGroupCols = list_length(root->parse->groupClause);
numGroups = estimate_num_groups(root,
get_sortgrouplist_exprs(root->parse->groupClause,
fpinfo->grouped_tlist),
input_rows, NULL);
/*
* Get the retrieved_rows and rows estimates. If there are HAVING
* quals, account for their selectivity.
*/
if (root->parse->havingQual)
{
/* Factor in the selectivity of the remotely-checked quals */
retrieved_rows =
clamp_row_est(numGroups *
clauselist_selectivity(root,
fpinfo->remote_conds,
0,
JOIN_INNER,
NULL,
false));
/* Factor in the selectivity of the locally-checked quals */
rows = clamp_row_est(retrieved_rows * fpinfo->local_conds_sel);
}
else
{
rows = retrieved_rows = numGroups;
}
/* Use width estimate made by the core code. */
width = foreignrel->reltarget->width;
/*-----
* Startup cost includes:
* 1. Startup cost for underneath input relation, adjusted for
* tlist replacement by apply_scanjoin_target_to_paths()
* 2. Cost of performing aggregation, per cost_agg()
*-----
*/
startup_cost = ofpinfo->rel_startup_cost;
startup_cost += outerrel->reltarget->cost.startup;
startup_cost += aggcosts.transCost.startup;
startup_cost += aggcosts.transCost.per_tuple * input_rows;
startup_cost += aggcosts.finalCost.startup;
startup_cost += (cpu_operator_cost * numGroupCols) * input_rows;
/*-----
* Run time cost includes:
* 1. Run time cost of underneath input relation, adjusted for
* tlist replacement by apply_scanjoin_target_to_paths()
* 2. Run time cost of performing aggregation, per cost_agg()
*-----
*/
run_cost = ofpinfo->rel_total_cost - ofpinfo->rel_startup_cost;
run_cost += outerrel->reltarget->cost.per_tuple * input_rows;
run_cost += aggcosts.finalCost.per_tuple * numGroups;
run_cost += cpu_tuple_cost * numGroups;
/* Account for the eval cost of HAVING quals, if any */
if (root->parse->havingQual)
{
QualCost remote_cost;
/* Add in the eval cost of the remotely-checked quals */
cost_qual_eval(&remote_cost, fpinfo->remote_conds, root);
startup_cost += remote_cost.startup;
run_cost += remote_cost.per_tuple * numGroups;
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
}
/* Add in tlist eval cost for each output row */
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
else
{
Cost cpu_per_tuple;
/* Use rows/width estimates made by set_baserel_size_estimates. */
rows = foreignrel->rows;
width = foreignrel->reltarget->width;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most foreignrel->tuples.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, foreignrel->tuples);
/*
* Cost as though this were a seqscan, which is pessimistic. We
* effectively imagine the local_conds are being evaluated
* remotely, too.
*/
startup_cost = 0;
run_cost = 0;
run_cost += seq_page_cost * foreignrel->pages;
startup_cost += foreignrel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost + foreignrel->baserestrictcost.per_tuple;
run_cost += cpu_per_tuple * foreignrel->tuples;
/* Add in tlist eval cost for each output row */
startup_cost += foreignrel->reltarget->cost.startup;
run_cost += foreignrel->reltarget->cost.per_tuple * rows;
}
/*
* Without remote estimates, we have no real way to estimate the cost
* of generating sorted output. It could be free if the query plan
* the remote side would have chosen generates properly-sorted output
* anyway, but in most cases it will cost something. Estimate a value
* high enough that we won't pick the sorted path when the ordering
* isn't locally useful, but low enough that we'll err on the side of
* pushing down the ORDER BY clause when it's useful to do so.
*/
if (pathkeys != NIL)
{
if (IS_UPPER_REL(foreignrel))
{
Assert(foreignrel->reloptkind == RELOPT_UPPER_REL &&
fpinfo->stage == UPPERREL_GROUP_AGG);
adjust_foreign_grouping_path_cost(root, pathkeys,
retrieved_rows, width,
fpextra->limit_tuples,
&startup_cost, &run_cost);
}
else
{
startup_cost *= DEFAULT_FDW_SORT_MULTIPLIER;
run_cost *= DEFAULT_FDW_SORT_MULTIPLIER;
}
}
total_cost = startup_cost + run_cost;
/* Adjust the cost estimates if we have LIMIT */
if (fpextra && fpextra->has_limit)
{
adjust_limit_rows_costs(&rows, &startup_cost, &total_cost,
fpextra->offset_est, fpextra->count_est);
retrieved_rows = rows;
}
}
/*
* If this includes the final sort step, the given target, which will be
* applied to the resulting path, might have different expressions from
* the foreignrel's reltarget (see make_sort_input_target()); adjust tlist
* eval costs.
*/
if (fpextra && fpextra->has_final_sort &&
fpextra->target != foreignrel->reltarget)
{
QualCost oldcost = foreignrel->reltarget->cost;
QualCost newcost = fpextra->target->cost;
startup_cost += newcost.startup - oldcost.startup;
total_cost += newcost.startup - oldcost.startup;
total_cost += (newcost.per_tuple - oldcost.per_tuple) * rows;
}
/*
* Cache the retrieved rows and cost estimates for scans, joins, or
* groupings without any parameterization, pathkeys, or additional
* post-scan/join-processing steps, before adding the costs for
* transferring data from the foreign server. These estimates are useful
* for costing remote joins involving this relation or costing other
* remote operations on this relation such as remote sorts and remote
* LIMIT restrictions, when the costs can not be obtained from the foreign
* server. This function will be called at least once for every foreign
* relation without any parameterization, pathkeys, or additional
* post-scan/join-processing steps.
*/
if (pathkeys == NIL && param_join_conds == NIL && fpextra == NULL)
{
fpinfo->retrieved_rows = retrieved_rows;
fpinfo->rel_startup_cost = startup_cost;
fpinfo->rel_total_cost = total_cost;
}
/*
* Add some additional cost factors to account for connection overhead
* (fdw_startup_cost), transferring data across the network
* (fdw_tuple_cost per retrieved row), and local manipulation of the data
* (cpu_tuple_cost per retrieved row).
*/
startup_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_tuple_cost * retrieved_rows;
total_cost += cpu_tuple_cost * retrieved_rows;
/*
* If we have LIMIT, we should prefer performing the restriction remotely
* rather than locally, as the former avoids extra row fetches from the
* remote that the latter might cause. But since the core code doesn't
* account for such fetches when estimating the costs of the local
* restriction (see create_limit_path()), there would be no difference
* between the costs of the local restriction and the costs of the remote
* restriction estimated above if we don't use remote estimates (except
* for the case where the foreignrel is a grouping relation, the given
* pathkeys is not NIL, and the effects of a bounded sort for that rel is
* accounted for in costing the remote restriction). Tweak the costs of
* the remote restriction to ensure we'll prefer it if LIMIT is a useful
* one.
*/
if (!fpinfo->use_remote_estimate &&
fpextra && fpextra->has_limit &&
fpextra->limit_tuples > 0 &&
fpextra->limit_tuples < fpinfo->rows)
{
Assert(fpinfo->rows > 0);
total_cost -= (total_cost - startup_cost) * 0.05 *
(fpinfo->rows - fpextra->limit_tuples) / fpinfo->rows;
}
/* Return results. */
*p_rows = rows;
*p_width = width;
*p_startup_cost = startup_cost;
*p_total_cost = total_cost;
}
/*
* Estimate costs of executing a SQL statement remotely.
* The given "sql" must be an EXPLAIN command.
*/
static void
get_remote_estimate(const char *sql, PGconn *conn,
double *rows, int *width,
Cost *startup_cost, Cost *total_cost)
{
PGresult *volatile res = NULL;
/* PGresult must be released before leaving this function. */
PG_TRY();
{
char *line;
char *p;
int n;
/*
* Execute EXPLAIN remotely.
*/
res = pgfdw_exec_query(conn, sql);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql);
/*
* Extract cost numbers for topmost plan node. Note we search for a
* left paren from the end of the line to avoid being confused by
* other uses of parentheses.
*/
line = PQgetvalue(res, 0, 0);
p = strrchr(line, '(');
if (p == NULL)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
n = sscanf(p, "(cost=%lf..%lf rows=%lf width=%d)",
startup_cost, total_cost, rows, width);
if (n != 4)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Adjust the cost estimates of a foreign grouping path to include the cost of
* generating properly-sorted output.
*/
static void
adjust_foreign_grouping_path_cost(PlannerInfo *root,
List *pathkeys,
double retrieved_rows,
double width,
double limit_tuples,
Cost *p_startup_cost,
Cost *p_run_cost)
{
/*
* If the GROUP BY clause isn't sort-able, the plan chosen by the remote
* side is unlikely to generate properly-sorted output, so it would need
* an explicit sort; adjust the given costs with cost_sort(). Likewise,
* if the GROUP BY clause is sort-able but isn't a superset of the given
* pathkeys, adjust the costs with that function. Otherwise, adjust the
* costs by applying the same heuristic as for the scan or join case.
*/
if (!grouping_is_sortable(root->parse->groupClause) ||
!pathkeys_contained_in(pathkeys, root->group_pathkeys))
{
Path sort_path; /* dummy for result of cost_sort */
cost_sort(&sort_path,
root,
pathkeys,
*p_startup_cost + *p_run_cost,
retrieved_rows,
width,
0.0,
work_mem,
limit_tuples);
*p_startup_cost = sort_path.startup_cost;
*p_run_cost = sort_path.total_cost - sort_path.startup_cost;
}
else
{
/*
* The default extra cost seems too large for foreign-grouping cases;
* add 1/4th of that default.
*/
double sort_multiplier = 1.0 + (DEFAULT_FDW_SORT_MULTIPLIER
- 1.0) * 0.25;
*p_startup_cost *= sort_multiplier;
*p_run_cost *= sort_multiplier;
}
}
/*
* Detect whether we want to process an EquivalenceClass member.
*
* This is a callback for use by generate_implied_equalities_for_column.
*/
static bool
ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, EquivalenceMember *em,
void *arg)
{
ec_member_foreign_arg *state = (ec_member_foreign_arg *) arg;
Expr *expr = em->em_expr;
/*
* If we've identified what we're processing in the current scan, we only
* want to match that expression.
*/
if (state->current != NULL)
return equal(expr, state->current);
/*
* Otherwise, ignore anything we've already processed.
*/
if (list_member(state->already_used, expr))
return false;
/* This is the new target to process. */
state->current = expr;
return true;
}
/*
* Create cursor for node's query with current parameter values.
*/
static void
create_cursor(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = fsstate->numParams;
const char **values = fsstate->param_values;
PGconn *conn = fsstate->conn;
StringInfoData buf;
PGresult *res;
/*
* Construct array of query parameter values in text format. We do the
* conversions in the short-lived per-tuple context, so as not to cause a
* memory leak over repeated scans.
*/
if (numParams > 0)
{
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
process_query_params(econtext,
fsstate->param_flinfo,
fsstate->param_exprs,
values);
MemoryContextSwitchTo(oldcontext);
}
/* Construct the DECLARE CURSOR command */
initStringInfo(&buf);
appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s",
fsstate->cursor_number, fsstate->query);
/*
* Notice that we pass NULL for paramTypes, thus forcing the remote server
* to infer types for all parameters. Since we explicitly cast every
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
*/
if (!PQsendQueryParams(conn, buf.data, numParams,
NULL, values, NULL, NULL, 0))
pgfdw_report_error(ERROR, NULL, conn, false, buf.data);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(conn, buf.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, fsstate->query);
PQclear(res);
/* Mark the cursor as created, and show no tuples have been retrieved */
fsstate->cursor_exists = true;
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
/* Clean up */
pfree(buf.data);
}
/*
* Fetch some more rows from the node's cursor.
*/
static void
fetch_more_data(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
PGresult *volatile res = NULL;
MemoryContext oldcontext;
/*
* We'll store the tuples in the batch_cxt. First, flush the previous
* batch.
*/
fsstate->tuples = NULL;
MemoryContextReset(fsstate->batch_cxt);
oldcontext = MemoryContextSwitchTo(fsstate->batch_cxt);
/* PGresult must be released before leaving this function. */
PG_TRY();
{
PGconn *conn = fsstate->conn;
char sql[64];
int numrows;
int i;
snprintf(sql, sizeof(sql), "FETCH %d FROM c%u",
fsstate->fetch_size, fsstate->cursor_number);
res = pgfdw_exec_query(conn, sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, fsstate->query);
/* Convert the data into HeapTuples */
numrows = PQntuples(res);
fsstate->tuples = (HeapTuple *) palloc0(numrows * sizeof(HeapTuple));
fsstate->num_tuples = numrows;
fsstate->next_tuple = 0;
for (i = 0; i < numrows; i++)
{
Assert(IsA(node->ss.ps.plan, ForeignScan));
fsstate->tuples[i] =
make_tuple_from_result_row(res, i,
fsstate->rel,
fsstate->attinmeta,
fsstate->retrieved_attrs,
node,
fsstate->temp_cxt);
}
/* Update fetch_ct_2 */
if (fsstate->fetch_ct_2 < 2)
fsstate->fetch_ct_2++;
/* Must be EOF if we didn't get as many tuples as we asked for. */
fsstate->eof_reached = (numrows < fsstate->fetch_size);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcontext);
}
/*
* Force assorted GUC parameters to settings that ensure that we'll output
* data values in a form that is unambiguous to the remote server.
*
* This is rather expensive and annoying to do once per row, but there's
* little choice if we want to be sure values are transmitted accurately;
* we can't leave the settings in place between rows for fear of affecting
* user-visible computations.
*
* We use the equivalent of a function SET option to allow the settings to
* persist only until the caller calls reset_transmission_modes(). If an
* error is thrown in between, guc.c will take care of undoing the settings.
*
* The return value is the nestlevel that must be passed to
* reset_transmission_modes() to undo things.
*/
int
set_transmission_modes(void)
{
int nestlevel = NewGUCNestLevel();
/*
* The values set here should match what pg_dump does. See also
* configure_remote_session in connection.c.
*/
if (DateStyle != USE_ISO_DATES)
(void) set_config_option("datestyle", "ISO",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
if (IntervalStyle != INTSTYLE_POSTGRES)
(void) set_config_option("intervalstyle", "postgres",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
if (extra_float_digits < 3)
(void) set_config_option("extra_float_digits", "3",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0, false);
return nestlevel;
}
/*
* Undo the effects of set_transmission_modes().
*/
void
reset_transmission_modes(int nestlevel)
{
AtEOXact_GUC(true, nestlevel);
}
/*
* Utility routine to close a cursor.
*/
static void
close_cursor(PGconn *conn, unsigned int cursor_number)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "CLOSE c%u", cursor_number);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_exec_query(conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, sql);
PQclear(res);
}
/*
* create_foreign_modify
* Construct an execution state of a foreign insert/update/delete
* operation
*/
static PgFdwModifyState *
create_foreign_modify(EState *estate,
RangeTblEntry *rte,
ResultRelInfo *resultRelInfo,
CmdType operation,
Plan *subplan,
char *query,
List *target_attrs,
bool has_returning,
List *retrieved_attrs)
{
PgFdwModifyState *fmstate;
Relation rel = resultRelInfo->ri_RelationDesc;
TupleDesc tupdesc = RelationGetDescr(rel);
Oid userid;
ForeignTable *table;
UserMapping *user;
AttrNumber n_params;
Oid typefnoid;
bool isvarlena;
ListCell *lc;
/* Begin constructing PgFdwModifyState. */
fmstate = (PgFdwModifyState *) palloc0(sizeof(PgFdwModifyState));
fmstate->rel = rel;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
table = GetForeignTable(RelationGetRelid(rel));
user = GetUserMapping(userid, table->serverid);
/* Open connection; report that we'll create a prepared statement. */
fmstate->conn = GetConnection(user, true);
fmstate->p_name = NULL; /* prepared statement not made yet */
/* Set up remote query information. */
fmstate->query = query;
fmstate->target_attrs = target_attrs;
fmstate->has_returning = has_returning;
fmstate->retrieved_attrs = retrieved_attrs;
/* Create context for per-tuple temp workspace. */
fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/* Prepare for input conversion of RETURNING results. */
if (fmstate->has_returning)
fmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
/* Prepare for output conversion of parameters used in prepared stmt. */
n_params = list_length(fmstate->target_attrs) + 1;
fmstate->p_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * n_params);
fmstate->p_nums = 0;
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
Assert(subplan != NULL);
/* Find the ctid resjunk column in the subplan's result */
fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist,
"ctid");
if (!AttributeNumberIsValid(fmstate->ctidAttno))
elog(ERROR, "could not find junk ctid column");
/* First transmittable parameter will be ctid */
getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
if (operation == CMD_INSERT || operation == CMD_UPDATE)
{
/* Set up for remaining transmittable parameters */
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
Assert(!attr->attisdropped);
getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
}
Assert(fmstate->p_nums <= n_params);
/* Initialize auxiliary state */
fmstate->aux_fmstate = NULL;
return fmstate;
}
/*
* execute_foreign_modify
* Perform foreign-table modification as required, and fetch RETURNING
* result if any. (This is the shared guts of postgresExecForeignInsert,
* postgresExecForeignUpdate, and postgresExecForeignDelete.)
*/
static TupleTableSlot *
execute_foreign_modify(EState *estate,
ResultRelInfo *resultRelInfo,
CmdType operation,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
ItemPointer ctid = NULL;
const char **p_values;
PGresult *res;
int n_rows;
/* The operation should be INSERT, UPDATE, or DELETE */
Assert(operation == CMD_INSERT ||
operation == CMD_UPDATE ||
operation == CMD_DELETE);
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/*
* For UPDATE/DELETE, get the ctid that was passed up as a resjunk column
*/
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
Datum datum;
bool isNull;
datum = ExecGetJunkAttribute(planSlot,
fmstate->ctidAttno,
&isNull);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
ctid = (ItemPointer) DatumGetPointer(datum);
}
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate, ctid, slot);
/*
* Execute the prepared statement.
*/
if (!PQsendQueryPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0))
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/*
* Return NULL if nothing was inserted/updated/deleted on the remote end
*/
return (n_rows > 0) ? slot : NULL;
}
/*
* prepare_foreign_modify
* Establish a prepared statement for execution of INSERT/UPDATE/DELETE
*/
static void
prepare_foreign_modify(PgFdwModifyState *fmstate)
{
char prep_name[NAMEDATALEN];
char *p_name;
PGresult *res;
/* Construct name we'll use for the prepared statement. */
snprintf(prep_name, sizeof(prep_name), "pgsql_fdw_prep_%u",
GetPrepStmtNumber(fmstate->conn));
p_name = pstrdup(prep_name);
/*
* We intentionally do not specify parameter types here, but leave the
* remote server to derive them by default. This avoids possible problems
* with the remote server using different type OIDs than we do. All of
* the prepared statements we use in this module are simple enough that
* the remote server will make the right choices.
*/
if (!PQsendPrepare(fmstate->conn,
p_name,
fmstate->query,
0,
NULL))
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
PQclear(res);
/* This action shows that the prepare has been done. */
fmstate->p_name = p_name;
}
/*
* convert_prep_stmt_params
* Create array of text strings representing parameter values
*
* tupleid is ctid to send, or NULL if none
* slot is slot to get remaining parameters from, or NULL if none
*
* Data is constructed in temp_cxt; caller should reset that after use.
*/
static const char **
convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot)
{
const char **p_values;
int pindex = 0;
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(fmstate->temp_cxt);
p_values = (const char **) palloc(sizeof(char *) * fmstate->p_nums);
/* 1st parameter should be ctid, if it's in use */
if (tupleid != NULL)
{
/* don't need set_transmission_modes for TID output */
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
PointerGetDatum(tupleid));
pindex++;
}
/* get following parameters from slot */
if (slot != NULL && fmstate->target_attrs != NIL)
{
int nestlevel;
ListCell *lc;
nestlevel = set_transmission_modes();
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Datum value;
bool isnull;
value = slot_getattr(slot, attnum, &isnull);
if (isnull)
p_values[pindex] = NULL;
else
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
value);
pindex++;
}
reset_transmission_modes(nestlevel);
}
Assert(pindex == fmstate->p_nums);
MemoryContextSwitchTo(oldcontext);
return p_values;
}
/*
* store_returning_result
* Store the result of a RETURNING clause
*
* On error, be sure to release the PGresult on the way out. Callers do not
* have PG_TRY blocks to ensure this happens.
*/
static void
store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res)
{
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(res, 0,
fmstate->rel,
fmstate->attinmeta,
fmstate->retrieved_attrs,
NULL,
fmstate->temp_cxt);
/*
* The returning slot will not necessarily be suitable to store
* heaptuples directly, so allow for conversion.
*/
ExecForceStoreHeapTuple(newtup, slot, true);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* finish_foreign_modify
* Release resources for a foreign insert/update/delete operation
*/
static void
finish_foreign_modify(PgFdwModifyState *fmstate)
{
Assert(fmstate != NULL);
/* If we created a prepared statement, destroy it */
if (fmstate->p_name)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "DEALLOCATE %s", fmstate->p_name);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_exec_query(fmstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, sql);
PQclear(res);
fmstate->p_name = NULL;
}
/* Release remote connection */
ReleaseConnection(fmstate->conn);
fmstate->conn = NULL;
}
/*
* build_remote_returning
* Build a RETURNING targetlist of a remote query for performing an
* UPDATE/DELETE .. RETURNING on a join directly
*/
static List *
build_remote_returning(Index rtindex, Relation rel, List *returningList)
{
bool have_wholerow = false;
List *tlist = NIL;
List *vars;
ListCell *lc;
Assert(returningList);
vars = pull_var_clause((Node *) returningList, PVC_INCLUDE_PLACEHOLDERS);
/*
* If there's a whole-row reference to the target relation, then we'll
* need all the columns of the relation.
*/
foreach(lc, vars)
{
Var *var = (Var *) lfirst(lc);
if (IsA(var, Var) &&
var->varno == rtindex &&
var->varattno == InvalidAttrNumber)
{
have_wholerow = true;
break;
}
}
if (have_wholerow)
{
TupleDesc tupdesc = RelationGetDescr(rel);
int i;
for (i = 1; i <= tupdesc->natts; i++)
{
Form_pg_attribute attr = TupleDescAttr(tupdesc, i - 1);
Var *var;
/* Ignore dropped attributes. */
if (attr->attisdropped)
continue;
var = makeVar(rtindex,
i,
attr->atttypid,
attr->atttypmod,
attr->attcollation,
0);
tlist = lappend(tlist,
makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
NULL,
false));
}
}
/* Now add any remaining columns to tlist. */
foreach(lc, vars)
{
Var *var = (Var *) lfirst(lc);
/*
* No need for whole-row references to the target relation. We don't
* need system columns other than ctid and oid either, since those are
* set locally.
*/
if (IsA(var, Var) &&
var->varno == rtindex &&
var->varattno <= InvalidAttrNumber &&
var->varattno != SelfItemPointerAttributeNumber)
continue; /* don't need it */
if (tlist_member((Expr *) var, tlist))
continue; /* already got it */
tlist = lappend(tlist,
makeTargetEntry((Expr *) var,
list_length(tlist) + 1,
NULL,
false));
}
list_free(vars);
return tlist;
}
/*
* rebuild_fdw_scan_tlist
* Build new fdw_scan_tlist of given foreign-scan plan node from given
* tlist
*
* There might be columns that the fdw_scan_tlist of the given foreign-scan
* plan node contains that the given tlist doesn't. The fdw_scan_tlist would
* have contained resjunk columns such as 'ctid' of the target relation and
* 'wholerow' of non-target relations, but the tlist might not contain them,
* for example. So, adjust the tlist so it contains all the columns specified
* in the fdw_scan_tlist; else setrefs.c will get confused.
*/
static void
rebuild_fdw_scan_tlist(ForeignScan *fscan, List *tlist)
{
List *new_tlist = tlist;
List *old_tlist = fscan->fdw_scan_tlist;
ListCell *lc;
foreach(lc, old_tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
if (tlist_member(tle->expr, new_tlist))
continue; /* already got it */
new_tlist = lappend(new_tlist,
makeTargetEntry(tle->expr,
list_length(new_tlist) + 1,
NULL,
false));
}
fscan->fdw_scan_tlist = new_tlist;
}
/*
* Execute a direct UPDATE/DELETE statement.
*/
static void
execute_dml_stmt(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = dmstate->numParams;
const char **values = dmstate->param_values;
/*
* Construct array of query parameter values in text format.
*/
if (numParams > 0)
process_query_params(econtext,
dmstate->param_flinfo,
dmstate->param_exprs,
values);
/*
* Notice that we pass NULL for paramTypes, thus forcing the remote server
* to infer types for all parameters. Since we explicitly cast every
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
*/
if (!PQsendQueryParams(dmstate->conn, dmstate->query, numParams,
NULL, values, NULL, NULL, 0))
pgfdw_report_error(ERROR, NULL, dmstate->conn, false, dmstate->query);
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
dmstate->result = pgfdw_get_result(dmstate->conn, dmstate->query);
if (PQresultStatus(dmstate->result) !=
(dmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, dmstate->result, dmstate->conn, true,
dmstate->query);
/* Get the number of rows affected. */
if (dmstate->has_returning)
dmstate->num_tuples = PQntuples(dmstate->result);
else
dmstate->num_tuples = atoi(PQcmdTuples(dmstate->result));
}
/*
* Get the result of a RETURNING clause.
*/
static TupleTableSlot *
get_returning_data(ForeignScanState *node)
{
PgFdwDirectModifyState *dmstate = (PgFdwDirectModifyState *) node->fdw_state;
EState *estate = node->ss.ps.state;
ResultRelInfo *resultRelInfo = estate->es_result_relation_info;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
TupleTableSlot *resultSlot;
Assert(resultRelInfo->ri_projectReturning);
/* If we didn't get any tuples, must be end of data. */
if (dmstate->next_tuple >= dmstate->num_tuples)
return ExecClearTuple(slot);
/* Increment the command es_processed count if necessary. */
if (dmstate->set_processed)
estate->es_processed += 1;
/*
* Store a RETURNING tuple. If has_returning is false, just emit a dummy
* tuple. (has_returning is false when the local query is of the form
* "UPDATE/DELETE .. RETURNING 1" for example.)
*/
if (!dmstate->has_returning)
{
ExecStoreAllNullTuple(slot);
resultSlot = slot;
}
else
{
/*
* On error, be sure to release the PGresult on the way out. Callers
* do not have PG_TRY blocks to ensure this happens.
*/
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(dmstate->result,
dmstate->next_tuple,
dmstate->rel,
dmstate->attinmeta,
dmstate->retrieved_attrs,
node,
dmstate->temp_cxt);
ExecStoreHeapTuple(newtup, slot, false);
}
PG_CATCH();
{
if (dmstate->result)
PQclear(dmstate->result);
PG_RE_THROW();
}
PG_END_TRY();
/* Get the updated/deleted tuple. */
if (dmstate->rel)
resultSlot = slot;
else
resultSlot = apply_returning_filter(dmstate, slot, estate);
}
dmstate->next_tuple++;
/* Make slot available for evaluation of the local query RETURNING list. */
resultRelInfo->ri_projectReturning->pi_exprContext->ecxt_scantuple =
resultSlot;
return slot;
}
/*
* Initialize a filter to extract an updated/deleted tuple from a scan tuple.
*/
static void
init_returning_filter(PgFdwDirectModifyState *dmstate,
List *fdw_scan_tlist,
Index rtindex)
{
TupleDesc resultTupType = RelationGetDescr(dmstate->resultRel);
ListCell *lc;
int i;
/*
* Calculate the mapping between the fdw_scan_tlist's entries and the
* result tuple's attributes.
*
* The "map" is an array of indexes of the result tuple's attributes in
* fdw_scan_tlist, i.e., one entry for every attribute of the result
* tuple. We store zero for any attributes that don't have the
* corresponding entries in that list, marking that a NULL is needed in
* the result tuple.
*
* Also get the indexes of the entries for ctid and oid if any.
*/
dmstate->attnoMap = (AttrNumber *)
palloc0(resultTupType->natts * sizeof(AttrNumber));
dmstate->ctidAttno = dmstate->oidAttno = 0;
i = 1;
dmstate->hasSystemCols = false;
foreach(lc, fdw_scan_tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
Var *var = (Var *) tle->expr;
Assert(IsA(var, Var));
/*
* If the Var is a column of the target relation to be retrieved from
* the foreign server, get the index of the entry.
*/
if (var->varno == rtindex &&
list_member_int(dmstate->retrieved_attrs, i))
{
int attrno = var->varattno;
if (attrno < 0)
{
/*
* We don't retrieve system columns other than ctid and oid.
*/
if (attrno == SelfItemPointerAttributeNumber)
dmstate->ctidAttno = i;
else
Assert(false);
dmstate->hasSystemCols = true;
}
else
{
/*
* We don't retrieve whole-row references to the target
* relation either.
*/
Assert(attrno > 0);
dmstate->attnoMap[attrno - 1] = i;
}
}
i++;
}
}
/*
* Extract and return an updated/deleted tuple from a scan tuple.
*/
static TupleTableSlot *
apply_returning_filter(PgFdwDirectModifyState *dmstate,
TupleTableSlot *slot,
EState *estate)
{
ResultRelInfo *relInfo = estate->es_result_relation_info;
TupleDesc resultTupType = RelationGetDescr(dmstate->resultRel);
TupleTableSlot *resultSlot;
Datum *values;
bool *isnull;
Datum *old_values;
bool *old_isnull;
int i;
/*
* Use the return tuple slot as a place to store the result tuple.
*/
resultSlot = ExecGetReturningSlot(estate, relInfo);
/*
* Extract all the values of the scan tuple.
*/
slot_getallattrs(slot);
old_values = slot->tts_values;
old_isnull = slot->tts_isnull;
/*
* Prepare to build the result tuple.
*/
ExecClearTuple(resultSlot);
values = resultSlot->tts_values;
isnull = resultSlot->tts_isnull;
/*
* Transpose data into proper fields of the result tuple.
*/
for (i = 0; i < resultTupType->natts; i++)
{
int j = dmstate->attnoMap[i];
if (j == 0)
{
values[i] = (Datum) 0;
isnull[i] = true;
}
else
{
values[i] = old_values[j - 1];
isnull[i] = old_isnull[j - 1];
}
}
/*
* Build the virtual tuple.
*/
ExecStoreVirtualTuple(resultSlot);
/*
* If we have any system columns to return, materialize a heap tuple in
* the slot from column values set above and install system columns in
* that tuple.
*/
if (dmstate->hasSystemCols)
{
HeapTuple resultTup = ExecFetchSlotHeapTuple(resultSlot, true, NULL);
/* ctid */
if (dmstate->ctidAttno)
{
ItemPointer ctid = NULL;
ctid = (ItemPointer) DatumGetPointer(old_values[dmstate->ctidAttno - 1]);
resultTup->t_self = *ctid;
}
/*
* And remaining columns
*
* Note: since we currently don't allow the target relation to appear
* on the nullable side of an outer join, any system columns wouldn't
* go to NULL.
*
* Note: no need to care about tableoid here because it will be
* initialized in ExecProcessReturning().
*/
HeapTupleHeaderSetXmin(resultTup->t_data, InvalidTransactionId);
HeapTupleHeaderSetXmax(resultTup->t_data, InvalidTransactionId);
HeapTupleHeaderSetCmin(resultTup->t_data, InvalidTransactionId);
}
/*
* And return the result tuple.
*/
return resultSlot;
}
/*
* Prepare for processing of parameters used in remote query.
*/
static void
prepare_query_params(PlanState *node,
List *fdw_exprs,
int numParams,
FmgrInfo **param_flinfo,
List **param_exprs,
const char ***param_values)
{
int i;
ListCell *lc;
Assert(numParams > 0);
/* Prepare for output conversion of parameters used in remote query. */
*param_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * numParams);
i = 0;
foreach(lc, fdw_exprs)
{
Node *param_expr = (Node *) lfirst(lc);
Oid typefnoid;
bool isvarlena;
getTypeOutputInfo(exprType(param_expr), &typefnoid, &isvarlena);
fmgr_info(typefnoid, &(*param_flinfo)[i]);
i++;
}
/*
* Prepare remote-parameter expressions for evaluation. (Note: in
* practice, we expect that all these expressions will be just Params, so
* we could possibly do something more efficient than using the full
* expression-eval machinery for this. But probably there would be little
* benefit, and it'd require postgres_fdw to know more than is desirable
* about Param evaluation.)
*/
*param_exprs = ExecInitExprList(fdw_exprs, node);
/* Allocate buffer for text form of query parameters. */
*param_values = (const char **) palloc0(numParams * sizeof(char *));
}
/*
* Construct array of query parameter values in text format.
*/
static void
process_query_params(ExprContext *econtext,
FmgrInfo *param_flinfo,
List *param_exprs,
const char **param_values)
{
int nestlevel;
int i;
ListCell *lc;
nestlevel = set_transmission_modes();
i = 0;
foreach(lc, param_exprs)
{
ExprState *expr_state = (ExprState *) lfirst(lc);
Datum expr_value;
bool isNull;
/* Evaluate the parameter expression */
expr_value = ExecEvalExpr(expr_state, econtext, &isNull);
/*
* Get string representation of each parameter value by invoking
* type-specific output function, unless the value is null.
*/
if (isNull)
param_values[i] = NULL;
else
param_values[i] = OutputFunctionCall(¶m_flinfo[i], expr_value);
i++;
}
reset_transmission_modes(nestlevel);
}
/*
* postgresAnalyzeForeignTable
* Test whether analyzing this foreign table is supported
*/
static bool
postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages)
{
ForeignTable *table;
UserMapping *user;
PGconn *conn;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Return the row-analysis function pointer */
*func = postgresAcquireSampleRowsFunc;
/*
* Now we have to get the number of pages. It's annoying that the ANALYZE
* API requires us to return that now, because it forces some duplication
* of effort between this routine and postgresAcquireSampleRowsFunc. But
* it's probably not worth redefining that API at this point.
*/
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
user = GetUserMapping(relation->rd_rel->relowner, table->serverid);
conn = GetConnection(user, false);
/*
* Construct command to get page count for relation.
*/
initStringInfo(&sql);
deparseAnalyzeSizeSql(&sql, relation);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = pgfdw_exec_query(conn, sql.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
if (PQntuples(res) != 1 || PQnfields(res) != 1)
elog(ERROR, "unexpected result from deparseAnalyzeSizeSql query");
*totalpages = strtoul(PQgetvalue(res, 0, 0), NULL, 10);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return true;
}
/*
* Acquire a random sample of rows from foreign table managed by postgres_fdw.
*
* We fetch the whole table from the remote side and pick out some sample rows.
*
* Selected rows are returned in the caller-allocated array rows[],
* which must have at least targrows entries.
* The actual number of rows selected is returned as the function result.
* We also count the total number of rows in the table and return it into
* *totalrows. Note that *totaldeadrows is always set to 0.
*
* Note that the returned list of rows is not always in order by physical
* position in the table. Therefore, correlation estimates derived later
* may be meaningless, but it's OK because we don't use the estimates
* currently (the planner only pays attention to correlation for indexscans).
*/
static int
postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows)
{
PgFdwAnalyzeState astate;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
PGconn *conn;
unsigned int cursor_number;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Initialize workspace state */
astate.rel = relation;
astate.attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(relation));
astate.rows = rows;
astate.targrows = targrows;
astate.numrows = 0;
astate.samplerows = 0;
astate.rowstoskip = -1; /* -1 means not set yet */
reservoir_init_selection_state(&astate.rstate, targrows);
/* Remember ANALYZE context, and create a per-tuple temp context */
astate.anl_cxt = CurrentMemoryContext;
astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"postgres_fdw temporary data",
ALLOCSET_SMALL_SIZES);
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
server = GetForeignServer(table->serverid);
user = GetUserMapping(relation->rd_rel->relowner, table->serverid);
conn = GetConnection(user, false);
/*
* Construct cursor that retrieves whole rows from remote.
*/
cursor_number = GetCursorNumber(conn);
initStringInfo(&sql);
appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number);
deparseAnalyzeSql(&sql, relation, &astate.retrieved_attrs);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = pgfdw_exec_query(conn, sql.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
PQclear(res);
res = NULL;
/* Retrieve and process rows a batch at a time. */
for (;;)
{
char fetch_sql[64];
int fetch_size;
int numrows;
int i;
ListCell *lc;
/* Allow users to cancel long query */
CHECK_FOR_INTERRUPTS();
/*
* XXX possible future improvement: if rowstoskip is large, we
* could issue a MOVE rather than physically fetching the rows,
* then just adjust rowstoskip and samplerows appropriately.
*/
/* The fetch size is arbitrary, but shouldn't be enormous. */
fetch_size = 100;
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "fetch_size") == 0)
{
fetch_size = strtol(defGetString(def), NULL, 10);
break;
}
}
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "fetch_size") == 0)
{
fetch_size = strtol(defGetString(def), NULL, 10);
break;
}
}
/* Fetch some rows */
snprintf(fetch_sql, sizeof(fetch_sql), "FETCH %d FROM c%u",
fetch_size, cursor_number);
res = pgfdw_exec_query(conn, fetch_sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
/* Process whatever we got. */
numrows = PQntuples(res);
for (i = 0; i < numrows; i++)
analyze_row_processor(res, i, &astate);
PQclear(res);
res = NULL;
/* Must be EOF if we didn't get all the rows requested. */
if (numrows < fetch_size)
break;
}
/* Close the cursor, just to be tidy. */
close_cursor(conn, cursor_number);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
/* We assume that we have no dead tuple. */
*totaldeadrows = 0.0;
/* We've retrieved all living tuples from foreign server. */
*totalrows = astate.samplerows;
/*
* Emit some interesting relation info
*/
ereport(elevel,
(errmsg("\"%s\": table contains %.0f rows, %d rows in sample",
RelationGetRelationName(relation),
astate.samplerows, astate.numrows)));
return astate.numrows;
}
/*
* Collect sample rows from the result of query.
* - Use all tuples in sample until target # of samples are collected.
* - Subsequently, replace already-sampled tuples randomly.
*/
static void
analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
{
int targrows = astate->targrows;
int pos; /* array index to store tuple in */
MemoryContext oldcontext;
/* Always increment sample row counter. */
astate->samplerows += 1;
/*
* Determine the slot where this sample row should be stored. Set pos to
* negative value to indicate the row should be skipped.
*/
if (astate->numrows < targrows)
{
/* First targrows rows are always included into the sample */
pos = astate->numrows++;
}
else
{
/*
* Now we start replacing tuples in the sample until we reach the end
* of the relation. Same algorithm as in acquire_sample_rows in
* analyze.c; see Jeff Vitter's paper.
*/
if (astate->rowstoskip < 0)
astate->rowstoskip = reservoir_get_next_S(&astate->rstate, astate->samplerows, targrows);
if (astate->rowstoskip <= 0)
{
/* Choose a random reservoir element to replace. */
pos = (int) (targrows * sampler_random_fract(astate->rstate.randstate));
Assert(pos >= 0 && pos < targrows);
heap_freetuple(astate->rows[pos]);
}
else
{
/* Skip this tuple. */
pos = -1;
}
astate->rowstoskip -= 1;
}
if (pos >= 0)
{
/*
* Create sample tuple from current result row, and store it in the
* position determined above. The tuple has to be created in anl_cxt.
*/
oldcontext = MemoryContextSwitchTo(astate->anl_cxt);
astate->rows[pos] = make_tuple_from_result_row(res, row,
astate->rel,
astate->attinmeta,
astate->retrieved_attrs,
NULL,
astate->temp_cxt);
MemoryContextSwitchTo(oldcontext);
}
}
/*
* Import a foreign schema
*/
static List *
postgresImportForeignSchema(ImportForeignSchemaStmt *stmt, Oid serverOid)
{
List *commands = NIL;
bool import_collate = true;
bool import_default = false;
bool import_not_null = true;
ForeignServer *server;
UserMapping *mapping;
PGconn *conn;
StringInfoData buf;
PGresult *volatile res = NULL;
int numrows,
i;
ListCell *lc;
/* Parse statement options */
foreach(lc, stmt->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "import_collate") == 0)
import_collate = defGetBoolean(def);
else if (strcmp(def->defname, "import_default") == 0)
import_default = defGetBoolean(def);
else if (strcmp(def->defname, "import_not_null") == 0)
import_not_null = defGetBoolean(def);
else
ereport(ERROR,
(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
errmsg("invalid option \"%s\"", def->defname)));
}
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
server = GetForeignServer(serverOid);
mapping = GetUserMapping(GetUserId(), server->serverid);
conn = GetConnection(mapping, false);
/* Don't attempt to import collation if remote server hasn't got it */
if (PQserverVersion(conn) < 90100)
import_collate = false;
/* Create workspace for strings */
initStringInfo(&buf);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
/* Check that the schema really exists */
appendStringInfoString(&buf, "SELECT 1 FROM pg_catalog.pg_namespace WHERE nspname = ");
deparseStringLiteral(&buf, stmt->remote_schema);
res = pgfdw_exec_query(conn, buf.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, buf.data);
if (PQntuples(res) != 1)
ereport(ERROR,
(errcode(ERRCODE_FDW_SCHEMA_NOT_FOUND),
errmsg("schema \"%s\" is not present on foreign server \"%s\"",
stmt->remote_schema, server->servername)));
PQclear(res);
res = NULL;
resetStringInfo(&buf);
/*
* Fetch all table data from this schema, possibly restricted by
* EXCEPT or LIMIT TO. (We don't actually need to pay any attention
* to EXCEPT/LIMIT TO here, because the core code will filter the
* statements we return according to those lists anyway. But it
* should save a few cycles to not process excluded tables in the
* first place.)
*
* Ignore table data for partitions and only include the definitions
* of the root partitioned tables to allow access to the complete
* remote data set locally in the schema imported.
*
* Note: because we run the connection with search_path restricted to
* pg_catalog, the format_type() and pg_get_expr() outputs will always
* include a schema name for types/functions in other schemas, which
* is what we want.
*/
if (import_collate)
appendStringInfoString(&buf,
"SELECT relname, "
" attname, "
" format_type(atttypid, atttypmod), "
" attnotnull, "
" pg_get_expr(adbin, adrelid), "
" collname, "
" collnsp.nspname "
"FROM pg_class c "
" JOIN pg_namespace n ON "
" relnamespace = n.oid "
" LEFT JOIN pg_attribute a ON "
" attrelid = c.oid AND attnum > 0 "
" AND NOT attisdropped "
" LEFT JOIN pg_attrdef ad ON "
" adrelid = c.oid AND adnum = attnum "
" LEFT JOIN pg_collation coll ON "
" coll.oid = attcollation "
" LEFT JOIN pg_namespace collnsp ON "
" collnsp.oid = collnamespace ");
else
appendStringInfoString(&buf,
"SELECT relname, "
" attname, "
" format_type(atttypid, atttypmod), "
" attnotnull, "
" pg_get_expr(adbin, adrelid), "
" NULL, NULL "
"FROM pg_class c "
" JOIN pg_namespace n ON "
" relnamespace = n.oid "
" LEFT JOIN pg_attribute a ON "
" attrelid = c.oid AND attnum > 0 "
" AND NOT attisdropped "
" LEFT JOIN pg_attrdef ad ON "
" adrelid = c.oid AND adnum = attnum ");
appendStringInfoString(&buf,
"WHERE c.relkind IN ("
CppAsString2(RELKIND_RELATION) ","
CppAsString2(RELKIND_VIEW) ","
CppAsString2(RELKIND_FOREIGN_TABLE) ","
CppAsString2(RELKIND_MATVIEW) ","
CppAsString2(RELKIND_PARTITIONED_TABLE) ") "
" AND n.nspname = ");
deparseStringLiteral(&buf, stmt->remote_schema);
/* Partitions are supported since Postgres 10 */
if (PQserverVersion(conn) >= 100000)
appendStringInfoString(&buf, " AND NOT c.relispartition ");
/* Apply restrictions for LIMIT TO and EXCEPT */
if (stmt->list_type == FDW_IMPORT_SCHEMA_LIMIT_TO ||
stmt->list_type == FDW_IMPORT_SCHEMA_EXCEPT)
{
bool first_item = true;
appendStringInfoString(&buf, " AND c.relname ");
if (stmt->list_type == FDW_IMPORT_SCHEMA_EXCEPT)
appendStringInfoString(&buf, "NOT ");
appendStringInfoString(&buf, "IN (");
/* Append list of table names within IN clause */
foreach(lc, stmt->table_list)
{
RangeVar *rv = (RangeVar *) lfirst(lc);
if (first_item)
first_item = false;
else
appendStringInfoString(&buf, ", ");
deparseStringLiteral(&buf, rv->relname);
}
appendStringInfoChar(&buf, ')');
}
/* Append ORDER BY at the end of query to ensure output ordering */
appendStringInfoString(&buf, " ORDER BY c.relname, a.attnum");
/* Fetch the data */
res = pgfdw_exec_query(conn, buf.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, buf.data);
/* Process results */
numrows = PQntuples(res);
/* note: incrementation of i happens in inner loop's while() test */
for (i = 0; i < numrows;)
{
char *tablename = PQgetvalue(res, i, 0);
bool first_item = true;
resetStringInfo(&buf);
appendStringInfo(&buf, "CREATE FOREIGN TABLE %s (\n",
quote_identifier(tablename));
/* Scan all rows for this table */
do
{
char *attname;
char *typename;
char *attnotnull;
char *attdefault;
char *collname;
char *collnamespace;
/* If table has no columns, we'll see nulls here */
if (PQgetisnull(res, i, 1))
continue;
attname = PQgetvalue(res, i, 1);
typename = PQgetvalue(res, i, 2);
attnotnull = PQgetvalue(res, i, 3);
attdefault = PQgetisnull(res, i, 4) ? (char *) NULL :
PQgetvalue(res, i, 4);
collname = PQgetisnull(res, i, 5) ? (char *) NULL :
PQgetvalue(res, i, 5);
collnamespace = PQgetisnull(res, i, 6) ? (char *) NULL :
PQgetvalue(res, i, 6);
if (first_item)
first_item = false;
else
appendStringInfoString(&buf, ",\n");
/* Print column name and type */
appendStringInfo(&buf, " %s %s",
quote_identifier(attname),
typename);
/*
* Add column_name option so that renaming the foreign table's
* column doesn't break the association to the underlying
* column.
*/
appendStringInfoString(&buf, " OPTIONS (column_name ");
deparseStringLiteral(&buf, attname);
appendStringInfoChar(&buf, ')');
/* Add COLLATE if needed */
if (import_collate && collname != NULL && collnamespace != NULL)
appendStringInfo(&buf, " COLLATE %s.%s",
quote_identifier(collnamespace),
quote_identifier(collname));
/* Add DEFAULT if needed */
if (import_default && attdefault != NULL)
appendStringInfo(&buf, " DEFAULT %s", attdefault);
/* Add NOT NULL if needed */
if (import_not_null && attnotnull[0] == 't')
appendStringInfoString(&buf, " NOT NULL");
}
while (++i < numrows &&
strcmp(PQgetvalue(res, i, 0), tablename) == 0);
/*
* Add server name and table-level options. We specify remote
* schema and table name as options (the latter to ensure that
* renaming the foreign table doesn't break the association).
*/
appendStringInfo(&buf, "\n) SERVER %s\nOPTIONS (",
quote_identifier(server->servername));
appendStringInfoString(&buf, "schema_name ");
deparseStringLiteral(&buf, stmt->remote_schema);
appendStringInfoString(&buf, ", table_name ");
deparseStringLiteral(&buf, tablename);
appendStringInfoString(&buf, ");");
commands = lappend(commands, pstrdup(buf.data));
}
/* Clean up */
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return commands;
}
/*
* Assess whether the join between inner and outer relations can be pushed down
* to the foreign server. As a side effect, save information we obtain in this
* function to PgFdwRelationInfo passed in.
*/
static bool
foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
RelOptInfo *outerrel, RelOptInfo *innerrel,
JoinPathExtraData *extra)
{
PgFdwRelationInfo *fpinfo;
PgFdwRelationInfo *fpinfo_o;
PgFdwRelationInfo *fpinfo_i;
ListCell *lc;
List *joinclauses;
/*
* We support pushing down INNER, LEFT, RIGHT and FULL OUTER joins.
* Constructing queries representing SEMI and ANTI joins is hard, hence
* not considered right now.
*/
if (jointype != JOIN_INNER && jointype != JOIN_LEFT &&
jointype != JOIN_RIGHT && jointype != JOIN_FULL)
return false;
/*
* If either of the joining relations is marked as unsafe to pushdown, the
* join can not be pushed down.
*/
fpinfo = (PgFdwRelationInfo *) joinrel->fdw_private;
fpinfo_o = (PgFdwRelationInfo *) outerrel->fdw_private;
fpinfo_i = (PgFdwRelationInfo *) innerrel->fdw_private;
if (!fpinfo_o || !fpinfo_o->pushdown_safe ||
!fpinfo_i || !fpinfo_i->pushdown_safe)
return false;
/*
* If joining relations have local conditions, those conditions are
* required to be applied before joining the relations. Hence the join can
* not be pushed down.
*/
if (fpinfo_o->local_conds || fpinfo_i->local_conds)
return false;
/*
* Merge FDW options. We might be tempted to do this after we have deemed
* the foreign join to be OK. But we must do this beforehand so that we
* know which quals can be evaluated on the foreign server, which might
* depend on shippable_extensions.
*/
fpinfo->server = fpinfo_o->server;
merge_fdw_options(fpinfo, fpinfo_o, fpinfo_i);
/*
* Separate restrict list into join quals and pushed-down (other) quals.
*
* Join quals belonging to an outer join must all be shippable, else we
* cannot execute the join remotely. Add such quals to 'joinclauses'.
*
* Add other quals to fpinfo->remote_conds if they are shippable, else to
* fpinfo->local_conds. In an inner join it's okay to execute conditions
* either locally or remotely; the same is true for pushed-down conditions
* at an outer join.
*
* Note we might return failure after having already scribbled on
* fpinfo->remote_conds and fpinfo->local_conds. That's okay because we
* won't consult those lists again if we deem the join unshippable.
*/
joinclauses = NIL;
foreach(lc, extra->restrictlist)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
bool is_remote_clause = is_foreign_expr(root, joinrel,
rinfo->clause);
if (IS_OUTER_JOIN(jointype) &&
!RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
{
if (!is_remote_clause)
return false;
joinclauses = lappend(joinclauses, rinfo);
}
else
{
if (is_remote_clause)
fpinfo->remote_conds = lappend(fpinfo->remote_conds, rinfo);
else
fpinfo->local_conds = lappend(fpinfo->local_conds, rinfo);
}
}
/*
* deparseExplicitTargetList() isn't smart enough to handle anything other
* than a Var. In particular, if there's some PlaceHolderVar that would
* need to be evaluated within this join tree (because there's an upper
* reference to a quantity that may go to NULL as a result of an outer
* join), then we can't try to push the join down because we'll fail when
* we get to deparseExplicitTargetList(). However, a PlaceHolderVar that
* needs to be evaluated *at the top* of this join tree is OK, because we
* can do that locally after fetching the results from the remote side.
*/
foreach(lc, root->placeholder_list)
{
PlaceHolderInfo *phinfo = lfirst(lc);
Relids relids;
/* PlaceHolderInfo refers to parent relids, not child relids. */
relids = IS_OTHER_REL(joinrel) ?
joinrel->top_parent_relids : joinrel->relids;
if (bms_is_subset(phinfo->ph_eval_at, relids) &&
bms_nonempty_difference(relids, phinfo->ph_eval_at))
return false;
}
/* Save the join clauses, for later use. */
fpinfo->joinclauses = joinclauses;
fpinfo->outerrel = outerrel;
fpinfo->innerrel = innerrel;
fpinfo->jointype = jointype;
/*
* By default, both the input relations are not required to be deparsed as
* subqueries, but there might be some relations covered by the input
* relations that are required to be deparsed as subqueries, so save the
* relids of those relations for later use by the deparser.
*/
fpinfo->make_outerrel_subquery = false;
fpinfo->make_innerrel_subquery = false;
Assert(bms_is_subset(fpinfo_o->lower_subquery_rels, outerrel->relids));
Assert(bms_is_subset(fpinfo_i->lower_subquery_rels, innerrel->relids));
fpinfo->lower_subquery_rels = bms_union(fpinfo_o->lower_subquery_rels,
fpinfo_i->lower_subquery_rels);
/*
* Pull the other remote conditions from the joining relations into join
* clauses or other remote clauses (remote_conds) of this relation
* wherever possible. This avoids building subqueries at every join step.
*
* For an inner join, clauses from both the relations are added to the
* other remote clauses. For LEFT and RIGHT OUTER join, the clauses from
* the outer side are added to remote_conds since those can be evaluated
* after the join is evaluated. The clauses from inner side are added to
* the joinclauses, since they need to be evaluated while constructing the
* join.
*
* For a FULL OUTER JOIN, the other clauses from either relation can not
* be added to the joinclauses or remote_conds, since each relation acts
* as an outer relation for the other.
*
* The joining sides can not have local conditions, thus no need to test
* shippability of the clauses being pulled up.
*/
switch (jointype)
{
case JOIN_INNER:
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
list_copy(fpinfo_i->remote_conds));
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
list_copy(fpinfo_o->remote_conds));
break;
case JOIN_LEFT:
fpinfo->joinclauses = list_concat(fpinfo->joinclauses,
list_copy(fpinfo_i->remote_conds));
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
list_copy(fpinfo_o->remote_conds));
break;
case JOIN_RIGHT:
fpinfo->joinclauses = list_concat(fpinfo->joinclauses,
list_copy(fpinfo_o->remote_conds));
fpinfo->remote_conds = list_concat(fpinfo->remote_conds,
list_copy(fpinfo_i->remote_conds));
break;
case JOIN_FULL:
/*
* In this case, if any of the input relations has conditions, we
* need to deparse that relation as a subquery so that the
* conditions can be evaluated before the join. Remember it in
* the fpinfo of this relation so that the deparser can take
* appropriate action. Also, save the relids of base relations
* covered by that relation for later use by the deparser.
*/
if (fpinfo_o->remote_conds)
{
fpinfo->make_outerrel_subquery = true;
fpinfo->lower_subquery_rels =
bms_add_members(fpinfo->lower_subquery_rels,
outerrel->relids);
}
if (fpinfo_i->remote_conds)
{
fpinfo->make_innerrel_subquery = true;
fpinfo->lower_subquery_rels =
bms_add_members(fpinfo->lower_subquery_rels,
innerrel->relids);
}
break;
default:
/* Should not happen, we have just checked this above */
elog(ERROR, "unsupported join type %d", jointype);
}
/*
* For an inner join, all restrictions can be treated alike. Treating the
* pushed down conditions as join conditions allows a top level full outer
* join to be deparsed without requiring subqueries.
*/
if (jointype == JOIN_INNER)
{
Assert(!fpinfo->joinclauses);
fpinfo->joinclauses = fpinfo->remote_conds;
fpinfo->remote_conds = NIL;
}
/* Mark that this join can be pushed down safely */
fpinfo->pushdown_safe = true;
/* Get user mapping */
if (fpinfo->use_remote_estimate)
{
if (fpinfo_o->use_remote_estimate)
fpinfo->user = fpinfo_o->user;
else
fpinfo->user = fpinfo_i->user;
}
else
fpinfo->user = NULL;
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* Set the string describing this join relation to be used in EXPLAIN
* output of corresponding ForeignScan.
*/
fpinfo->relation_name = makeStringInfo();
appendStringInfo(fpinfo->relation_name, "(%s) %s JOIN (%s)",
fpinfo_o->relation_name->data,
get_jointype_name(fpinfo->jointype),
fpinfo_i->relation_name->data);
/*
* Set the relation index. This is defined as the position of this
* joinrel in the join_rel_list list plus the length of the rtable list.
* Note that since this joinrel is at the end of the join_rel_list list
* when we are called, we can get the position by list_length.
*/
Assert(fpinfo->relation_index == 0); /* shouldn't be set yet */
fpinfo->relation_index =
list_length(root->parse->rtable) + list_length(root->join_rel_list);
return true;
}
static void
add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
Path *epq_path)
{
List *useful_pathkeys_list = NIL; /* List of all pathkeys */
ListCell *lc;
useful_pathkeys_list = get_useful_pathkeys_for_relation(root, rel);
/* Create one path for each set of pathkeys we found above. */
foreach(lc, useful_pathkeys_list)
{
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *useful_pathkeys = lfirst(lc);
Path *sorted_epq_path;
estimate_path_cost_size(root, rel, NIL, useful_pathkeys, NULL,
&rows, &width, &startup_cost, &total_cost);
/*
* The EPQ path must be at least as well sorted as the path itself, in
* case it gets used as input to a mergejoin.
*/
sorted_epq_path = epq_path;
if (sorted_epq_path != NULL &&
!pathkeys_contained_in(useful_pathkeys,
sorted_epq_path->pathkeys))
sorted_epq_path = (Path *)
create_sort_path(root,
rel,
sorted_epq_path,
useful_pathkeys,
-1.0);
if (IS_SIMPLE_REL(rel))
add_path(rel, (Path *)
create_foreignscan_path(root, rel,
NULL,
rows,
startup_cost,
total_cost,
useful_pathkeys,
rel->lateral_relids,
sorted_epq_path,
NIL));
else
add_path(rel, (Path *)
create_foreign_join_path(root, rel,
NULL,
rows,
startup_cost,
total_cost,
useful_pathkeys,
rel->lateral_relids,
sorted_epq_path,
NIL));
}
}
/*
* Parse options from foreign server and apply them to fpinfo.
*
* New options might also require tweaking merge_fdw_options().
*/
static void
apply_server_options(PgFdwRelationInfo *fpinfo)
{
ListCell *lc;
foreach(lc, fpinfo->server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
else if (strcmp(def->defname, "fdw_startup_cost") == 0)
fpinfo->fdw_startup_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "fdw_tuple_cost") == 0)
fpinfo->fdw_tuple_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "extensions") == 0)
fpinfo->shippable_extensions =
ExtractExtensionList(defGetString(def), false);
else if (strcmp(def->defname, "fetch_size") == 0)
fpinfo->fetch_size = strtol(defGetString(def), NULL, 10);
}
}
/*
* Parse options from foreign table and apply them to fpinfo.
*
* New options might also require tweaking merge_fdw_options().
*/
static void
apply_table_options(PgFdwRelationInfo *fpinfo)
{
ListCell *lc;
foreach(lc, fpinfo->table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
else if (strcmp(def->defname, "fetch_size") == 0)
fpinfo->fetch_size = strtol(defGetString(def), NULL, 10);
}
}
/*
* Merge FDW options from input relations into a new set of options for a join
* or an upper rel.
*
* For a join relation, FDW-specific information about the inner and outer
* relations is provided using fpinfo_i and fpinfo_o. For an upper relation,
* fpinfo_o provides the information for the input relation; fpinfo_i is
* expected to NULL.
*/
static void
merge_fdw_options(PgFdwRelationInfo *fpinfo,
const PgFdwRelationInfo *fpinfo_o,
const PgFdwRelationInfo *fpinfo_i)
{
/* We must always have fpinfo_o. */
Assert(fpinfo_o);
/* fpinfo_i may be NULL, but if present the servers must both match. */
Assert(!fpinfo_i ||
fpinfo_i->server->serverid == fpinfo_o->server->serverid);
/*
* Copy the server specific FDW options. (For a join, both relations come
* from the same server, so the server options should have the same value
* for both relations.)
*/
fpinfo->fdw_startup_cost = fpinfo_o->fdw_startup_cost;
fpinfo->fdw_tuple_cost = fpinfo_o->fdw_tuple_cost;
fpinfo->shippable_extensions = fpinfo_o->shippable_extensions;
fpinfo->use_remote_estimate = fpinfo_o->use_remote_estimate;
fpinfo->fetch_size = fpinfo_o->fetch_size;
/* Merge the table level options from either side of the join. */
if (fpinfo_i)
{
/*
* We'll prefer to use remote estimates for this join if any table
* from either side of the join is using remote estimates. This is
* most likely going to be preferred since they're already willing to
* pay the price of a round trip to get the remote EXPLAIN. In any
* case it's not entirely clear how we might otherwise handle this
* best.
*/
fpinfo->use_remote_estimate = fpinfo_o->use_remote_estimate ||
fpinfo_i->use_remote_estimate;
/*
* Set fetch size to maximum of the joining sides, since we are
* expecting the rows returned by the join to be proportional to the
* relation sizes.
*/
fpinfo->fetch_size = Max(fpinfo_o->fetch_size, fpinfo_i->fetch_size);
}
}
/*
* postgresGetForeignJoinPaths
* Add possible ForeignPath to joinrel, if join is safe to push down.
*/
static void
postgresGetForeignJoinPaths(PlannerInfo *root,
RelOptInfo *joinrel,
RelOptInfo *outerrel,
RelOptInfo *innerrel,
JoinType jointype,
JoinPathExtraData *extra)
{
PgFdwRelationInfo *fpinfo;
ForeignPath *joinpath;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
Path *epq_path; /* Path to create plan to be executed when
* EvalPlanQual gets triggered. */
/*
* Skip if this join combination has been considered already.
*/
if (joinrel->fdw_private)
return;
/*
* This code does not work for joins with lateral references, since those
* must have parameterized paths, which we don't generate yet.
*/
if (!bms_is_empty(joinrel->lateral_relids))
return;
/*
* Create unfinished PgFdwRelationInfo entry which is used to indicate
* that the join relation is already considered, so that we won't waste
* time in judging safety of join pushdown and adding the same paths again
* if found safe. Once we know that this join can be pushed down, we fill
* the entry.
*/
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
fpinfo->pushdown_safe = false;
joinrel->fdw_private = fpinfo;
/* attrs_used is only for base relations. */
fpinfo->attrs_used = NULL;
/*
* If there is a possibility that EvalPlanQual will be executed, we need
* to be able to reconstruct the row using scans of the base relations.
* GetExistingLocalJoinPath will find a suitable path for this purpose in
* the path list of the joinrel, if one exists. We must be careful to
* call it before adding any ForeignPath, since the ForeignPath might
* dominate the only suitable local path available. We also do it before
* calling foreign_join_ok(), since that function updates fpinfo and marks
* it as pushable if the join is found to be pushable.
*/
if (root->parse->commandType == CMD_DELETE ||
root->parse->commandType == CMD_UPDATE ||
root->rowMarks)
{
epq_path = GetExistingLocalJoinPath(joinrel);
if (!epq_path)
{
elog(DEBUG3, "could not push down foreign join because a local path suitable for EPQ checks was not found");
return;
}
}
else
epq_path = NULL;
if (!foreign_join_ok(root, joinrel, jointype, outerrel, innerrel, extra))
{
/* Free path required for EPQ if we copied one; we don't need it now */
if (epq_path)
pfree(epq_path);
return;
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
* The local conditions are applied after the join has been computed on
* the remote side like quals in WHERE clause, so pass jointype as
* JOIN_INNER.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
0,
JOIN_INNER,
NULL,
false);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* If we are going to estimate costs locally, estimate the join clause
* selectivity here while we have special join info.
*/
if (!fpinfo->use_remote_estimate)
fpinfo->joinclause_sel = clauselist_selectivity(root, fpinfo->joinclauses,
0, fpinfo->jointype,
extra->sjinfo,
false);
/* Estimate costs for bare join relation */
estimate_path_cost_size(root, joinrel, NIL, NIL, NULL,
&rows, &width, &startup_cost, &total_cost);
/* Now update this information in the joinrel */
joinrel->rows = rows;
joinrel->reltarget->width = width;
fpinfo->rows = rows;
fpinfo->width = width;
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
/*
* Create a new join path and add it to the joinrel which represents a
* join between foreign tables.
*/
joinpath = create_foreign_join_path(root,
joinrel,
NULL, /* default pathtarget */
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
joinrel->lateral_relids,
epq_path,
NIL); /* no fdw_private */
/* Add generated path into joinrel by add_path(). */
add_path(joinrel, (Path *) joinpath);
/* Consider pathkeys for the join relation */
add_paths_with_pathkeys_for_rel(root, joinrel, epq_path);
/* XXX Consider parameterized paths for the join relation */
}
/*
* Assess whether the aggregation, grouping and having operations can be pushed
* down to the foreign server. As a side effect, save information we obtain in
* this function to PgFdwRelationInfo of the input relation.
*/
static bool
foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel,
Node *havingQual)
{
Query *query = root->parse;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) grouped_rel->fdw_private;
PathTarget *grouping_target = grouped_rel->reltarget;
PgFdwRelationInfo *ofpinfo;
ListCell *lc;
int i;
List *tlist = NIL;
/* We currently don't support pushing Grouping Sets. */
if (query->groupingSets)
return false;
/* Get the fpinfo of the underlying scan relation. */
ofpinfo = (PgFdwRelationInfo *) fpinfo->outerrel->fdw_private;
/*
* If underlying scan relation has any local conditions, those conditions
* are required to be applied before performing aggregation. Hence the
* aggregate cannot be pushed down.
*/
if (ofpinfo->local_conds)
return false;
/*
* Examine grouping expressions, as well as other expressions we'd need to
* compute, and check whether they are safe to push down to the foreign
* server. All GROUP BY expressions will be part of the grouping target
* and thus there is no need to search for them separately. Add grouping
* expressions into target list which will be passed to foreign server.
*
* A tricky fine point is that we must not put any expression into the
* target list that is just a foreign param (that is, something that
* deparse.c would conclude has to be sent to the foreign server). If we
* do, the expression will also appear in the fdw_exprs list of the plan
* node, and setrefs.c will get confused and decide that the fdw_exprs
* entry is actually a reference to the fdw_scan_tlist entry, resulting in
* a broken plan. Somewhat oddly, it's OK if the expression contains such
* a node, as long as it's not at top level; then no match is possible.
*/
i = 0;
foreach(lc, grouping_target->exprs)
{
Expr *expr = (Expr *) lfirst(lc);
Index sgref = get_pathtarget_sortgroupref(grouping_target, i);
ListCell *l;
/* Check whether this expression is part of GROUP BY clause */
if (sgref && get_sortgroupref_clause_noerr(sgref, query->groupClause))
{
TargetEntry *tle;
/*
* If any GROUP BY expression is not shippable, then we cannot
* push down aggregation to the foreign server.
*/
if (!is_foreign_expr(root, grouped_rel, expr))
return false;
/*
* If it would be a foreign param, we can't put it into the tlist,
* so we have to fail.
*/
if (is_foreign_param(root, grouped_rel, expr))
return false;
/*
* Pushable, so add to tlist. We need to create a TLE for this
* expression and apply the sortgroupref to it. We cannot use
* add_to_flat_tlist() here because that avoids making duplicate
* entries in the tlist. If there are duplicate entries with
* distinct sortgrouprefs, we have to duplicate that situation in
* the output tlist.
*/
tle = makeTargetEntry(expr, list_length(tlist) + 1, NULL, false);
tle->ressortgroupref = sgref;
tlist = lappend(tlist, tle);
}
else
{
/*
* Non-grouping expression we need to compute. Can we ship it
* as-is to the foreign server?
*/
if (is_foreign_expr(root, grouped_rel, expr) &&
!is_foreign_param(root, grouped_rel, expr))
{
/* Yes, so add to tlist as-is; OK to suppress duplicates */
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
else
{
/* Not pushable as a whole; extract its Vars and aggregates */
List *aggvars;
aggvars = pull_var_clause((Node *) expr,
PVC_INCLUDE_AGGREGATES);
/*
* If any aggregate expression is not shippable, then we
* cannot push down aggregation to the foreign server. (We
* don't have to check is_foreign_param, since that certainly
* won't return true for any such expression.)
*/
if (!is_foreign_expr(root, grouped_rel, (Expr *) aggvars))
return false;
/*
* Add aggregates, if any, into the targetlist. Plain Vars
* outside an aggregate can be ignored, because they should be
* either same as some GROUP BY column or part of some GROUP
* BY expression. In either case, they are already part of
* the targetlist and thus no need to add them again. In fact
* including plain Vars in the tlist when they do not match a
* GROUP BY column would cause the foreign server to complain
* that the shipped query is invalid.
*/
foreach(l, aggvars)
{
Expr *expr = (Expr *) lfirst(l);
if (IsA(expr, Aggref))
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
}
}
i++;
}
/*
* Classify the pushable and non-pushable HAVING clauses and save them in
* remote_conds and local_conds of the grouped rel's fpinfo.
*/
if (havingQual)
{
ListCell *lc;
foreach(lc, (List *) havingQual)
{
Expr *expr = (Expr *) lfirst(lc);
RestrictInfo *rinfo;
/*
* Currently, the core code doesn't wrap havingQuals in
* RestrictInfos, so we must make our own.
*/
Assert(!IsA(expr, RestrictInfo));
rinfo = make_restrictinfo(expr,
true,
false,
false,
root->qual_security_level,
grouped_rel->relids,
NULL,
NULL);
if (is_foreign_expr(root, grouped_rel, expr))
fpinfo->remote_conds = lappend(fpinfo->remote_conds, rinfo);
else
fpinfo->local_conds = lappend(fpinfo->local_conds, rinfo);
}
}
/*
* If there are any local conditions, pull Vars and aggregates from it and
* check whether they are safe to pushdown or not.
*/
if (fpinfo->local_conds)
{
List *aggvars = NIL;
ListCell *lc;
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
aggvars = list_concat(aggvars,
pull_var_clause((Node *) rinfo->clause,
PVC_INCLUDE_AGGREGATES));
}
foreach(lc, aggvars)
{
Expr *expr = (Expr *) lfirst(lc);
/*
* If aggregates within local conditions are not safe to push
* down, then we cannot push down the query. Vars are already
* part of GROUP BY clause which are checked above, so no need to
* access them again here. Again, we need not check
* is_foreign_param for a foreign aggregate.
*/
if (IsA(expr, Aggref))
{
if (!is_foreign_expr(root, grouped_rel, expr))
return false;
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
}
}
/* Store generated targetlist */
fpinfo->grouped_tlist = tlist;
/* Safe to pushdown */
fpinfo->pushdown_safe = true;
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* Set the string describing this grouped relation to be used in EXPLAIN
* output of corresponding ForeignScan.
*/
fpinfo->relation_name = makeStringInfo();
appendStringInfo(fpinfo->relation_name, "Aggregate on (%s)",
ofpinfo->relation_name->data);
return true;
}
/*
* postgresGetForeignUpperPaths
* Add paths for post-join operations like aggregation, grouping etc. if
* corresponding operations are safe to push down.
*/
static void
postgresGetForeignUpperPaths(PlannerInfo *root, UpperRelationKind stage,
RelOptInfo *input_rel, RelOptInfo *output_rel,
void *extra)
{
PgFdwRelationInfo *fpinfo;
/*
* If input rel is not safe to pushdown, then simply return as we cannot
* perform any post-join operations on the foreign server.
*/
if (!input_rel->fdw_private ||
!((PgFdwRelationInfo *) input_rel->fdw_private)->pushdown_safe)
return;
/* Ignore stages we don't support; and skip any duplicate calls. */
if ((stage != UPPERREL_GROUP_AGG &&
stage != UPPERREL_ORDERED &&
stage != UPPERREL_FINAL) ||
output_rel->fdw_private)
return;
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
fpinfo->pushdown_safe = false;
fpinfo->stage = stage;
output_rel->fdw_private = fpinfo;
switch (stage)
{
case UPPERREL_GROUP_AGG:
add_foreign_grouping_paths(root, input_rel, output_rel,
(GroupPathExtraData *) extra);
break;
case UPPERREL_ORDERED:
add_foreign_ordered_paths(root, input_rel, output_rel);
break;
case UPPERREL_FINAL:
add_foreign_final_paths(root, input_rel, output_rel,
(FinalPathExtraData *) extra);
break;
default:
elog(ERROR, "unexpected upper relation: %d", (int) stage);
break;
}
}
/*
* add_foreign_grouping_paths
* Add foreign path for grouping and/or aggregation.
*
* Given input_rel represents the underlying scan. The paths are added to the
* given grouped_rel.
*/
static void
add_foreign_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *grouped_rel,
GroupPathExtraData *extra)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = grouped_rel->fdw_private;
ForeignPath *grouppath;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Nothing to be done, if there is no grouping or aggregation required. */
if (!parse->groupClause && !parse->groupingSets && !parse->hasAggs &&
!root->hasHavingQual)
return;
Assert(extra->patype == PARTITIONWISE_AGGREGATE_NONE ||
extra->patype == PARTITIONWISE_AGGREGATE_FULL);
/* save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* Assess if it is safe to push down aggregation and grouping.
*
* Use HAVING qual from extra. In case of child partition, it will have
* translated Vars.
*/
if (!foreign_grouping_ok(root, grouped_rel, extra->havingQual))
return;
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. (Currently we create just a single
* path here, but in future it would be possible that we build more paths
* such as pre-sorted paths as in postgresGetForeignPaths and
* postgresGetForeignJoinPaths.) The best we can do for these conditions
* is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
0,
JOIN_INNER,
NULL,
false);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/* Estimate the cost of push down */
estimate_path_cost_size(root, grouped_rel, NIL, NIL, NULL,
&rows, &width, &startup_cost, &total_cost);
/* Now update this information in the fpinfo */
fpinfo->rows = rows;
fpinfo->width = width;
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
/* Create and add foreign path to the grouping relation. */
grouppath = create_foreign_upper_path(root,
grouped_rel,
grouped_rel->reltarget,
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
NULL,
NIL); /* no fdw_private */
/* Add generated path into grouped_rel by add_path(). */
add_path(grouped_rel, (Path *) grouppath);
}
/*
* add_foreign_ordered_paths
* Add foreign paths for performing the final sort remotely.
*
* Given input_rel contains the source-data Paths. The paths are added to the
* given ordered_rel.
*/
static void
add_foreign_ordered_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *ordered_rel)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = ordered_rel->fdw_private;
PgFdwPathExtraData *fpextra;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *fdw_private;
ForeignPath *ordered_path;
ListCell *lc;
/* Shouldn't get here unless the query has ORDER BY */
Assert(parse->sortClause);
/* We don't support cases where there are any SRFs in the targetlist */
if (parse->hasTargetSRFs)
return;
/* Save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* If the input_rel is a base or join relation, we would already have
* considered pushing down the final sort to the remote server when
* creating pre-sorted foreign paths for that relation, because the
* query_pathkeys is set to the root->sort_pathkeys in that case (see
* standard_qp_callback()).
*/
if (input_rel->reloptkind == RELOPT_BASEREL ||
input_rel->reloptkind == RELOPT_JOINREL)
{
Assert(root->query_pathkeys == root->sort_pathkeys);
/* Safe to push down if the query_pathkeys is safe to push down */
fpinfo->pushdown_safe = ifpinfo->qp_is_pushdown_safe;
return;
}
/* The input_rel should be a grouping relation */
Assert(input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_GROUP_AGG);
/*
* We try to create a path below by extending a simple foreign path for
* the underlying grouping relation to perform the final sort remotely,
* which is stored into the fdw_private list of the resulting path.
*/
/* Assess if it is safe to push down the final sort */
foreach(lc, root->sort_pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc);
EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
Expr *sort_expr;
/*
* is_foreign_expr would detect volatile expressions as well, but
* checking ec_has_volatile here saves some cycles.
*/
if (pathkey_ec->ec_has_volatile)
return;
/* Get the sort expression for the pathkey_ec */
sort_expr = find_em_expr_for_input_target(root,
pathkey_ec,
input_rel->reltarget);
/* If it's unsafe to remote, we cannot push down the final sort */
if (!is_foreign_expr(root, input_rel, sort_expr))
return;
}
/* Safe to push down */
fpinfo->pushdown_safe = true;
/* Construct PgFdwPathExtraData */
fpextra = (PgFdwPathExtraData *) palloc0(sizeof(PgFdwPathExtraData));
fpextra->target = root->upper_targets[UPPERREL_ORDERED];
fpextra->has_final_sort = true;
/* Estimate the costs of performing the final sort remotely */
estimate_path_cost_size(root, input_rel, NIL, root->sort_pathkeys, fpextra,
&rows, &width, &startup_cost, &total_cost);
/*
* Build the fdw_private list that will be used by postgresGetForeignPlan.
* Items in the list must match order in enum FdwPathPrivateIndex.
*/
fdw_private = list_make2(makeInteger(true), makeInteger(false));
/* Create foreign ordering path */
ordered_path = create_foreign_upper_path(root,
input_rel,
root->upper_targets[UPPERREL_ORDERED],
rows,
startup_cost,
total_cost,
root->sort_pathkeys,
NULL, /* no extra plan */
fdw_private);
/* and add it to the ordered_rel */
add_path(ordered_rel, (Path *) ordered_path);
}
/*
* add_foreign_final_paths
* Add foreign paths for performing the final processing remotely.
*
* Given input_rel contains the source-data Paths. The paths are added to the
* given final_rel.
*/
static void
add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel,
RelOptInfo *final_rel,
FinalPathExtraData *extra)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = (PgFdwRelationInfo *) input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) final_rel->fdw_private;
bool has_final_sort = false;
List *pathkeys = NIL;
PgFdwPathExtraData *fpextra;
bool save_use_remote_estimate = false;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *fdw_private;
ForeignPath *final_path;
/*
* Currently, we only support this for SELECT commands
*/
if (parse->commandType != CMD_SELECT)
return;
/*
* No work if there is no FOR UPDATE/SHARE clause and if there is no need
* to add a LIMIT node
*/
if (!parse->rowMarks && !extra->limit_needed)
return;
/* We don't support cases where there are any SRFs in the targetlist */
if (parse->hasTargetSRFs)
return;
/* Save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* If there is no need to add a LIMIT node, there might be a ForeignPath
* in the input_rel's pathlist that implements all behavior of the query.
* Note: we would already have accounted for the query's FOR UPDATE/SHARE
* (if any) before we get here.
*/
if (!extra->limit_needed)
{
ListCell *lc;
Assert(parse->rowMarks);
/*
* Grouping and aggregation are not supported with FOR UPDATE/SHARE,
* so the input_rel should be a base, join, or ordered relation; and
* if it's an ordered relation, its input relation should be a base or
* join relation.
*/
Assert(input_rel->reloptkind == RELOPT_BASEREL ||
input_rel->reloptkind == RELOPT_JOINREL ||
(input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_ORDERED &&
(ifpinfo->outerrel->reloptkind == RELOPT_BASEREL ||
ifpinfo->outerrel->reloptkind == RELOPT_JOINREL)));
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
/*
* apply_scanjoin_target_to_paths() uses create_projection_path()
* to adjust each of its input paths if needed, whereas
* create_ordered_paths() uses apply_projection_to_path() to do
* that. So the former might have put a ProjectionPath on top of
* the ForeignPath; look through ProjectionPath and see if the
* path underneath it is ForeignPath.
*/
if (IsA(path, ForeignPath) ||
(IsA(path, ProjectionPath) &&
IsA(((ProjectionPath *) path)->subpath, ForeignPath)))
{
/*
* Create foreign final path; this gets rid of a
* no-longer-needed outer plan (if any), which makes the
* EXPLAIN output look cleaner
*/
final_path = create_foreign_upper_path(root,
path->parent,
path->pathtarget,
path->rows,
path->startup_cost,
path->total_cost,
path->pathkeys,
NULL, /* no extra plan */
NULL); /* no fdw_private */
/* and add it to the final_rel */
add_path(final_rel, (Path *) final_path);
/* Safe to push down */
fpinfo->pushdown_safe = true;
return;
}
}
/*
* If we get here it means no ForeignPaths; since we would already
* have considered pushing down all operations for the query to the
* remote server, give up on it.
*/
return;
}
Assert(extra->limit_needed);
/*
* If the input_rel is an ordered relation, replace the input_rel with its
* input relation
*/
if (input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_ORDERED)
{
input_rel = ifpinfo->outerrel;
ifpinfo = (PgFdwRelationInfo *) input_rel->fdw_private;
has_final_sort = true;
pathkeys = root->sort_pathkeys;
}
/* The input_rel should be a base, join, or grouping relation */
Assert(input_rel->reloptkind == RELOPT_BASEREL ||
input_rel->reloptkind == RELOPT_JOINREL ||
(input_rel->reloptkind == RELOPT_UPPER_REL &&
ifpinfo->stage == UPPERREL_GROUP_AGG));
/*
* We try to create a path below by extending a simple foreign path for
* the underlying base, join, or grouping relation to perform the final
* sort (if has_final_sort) and the LIMIT restriction remotely, which is
* stored into the fdw_private list of the resulting path. (We
* re-estimate the costs of sorting the underlying relation, if
* has_final_sort.)
*/
/*
* Assess if it is safe to push down the LIMIT and OFFSET to the remote
* server
*/
/*
* If the underlying relation has any local conditions, the LIMIT/OFFSET
* cannot be pushed down.
*/
if (ifpinfo->local_conds)
return;
/*
* Also, the LIMIT/OFFSET cannot be pushed down, if their expressions are
* not safe to remote.
*/
if (!is_foreign_expr(root, input_rel, (Expr *) parse->limitOffset) ||
!is_foreign_expr(root, input_rel, (Expr *) parse->limitCount))
return;
/* Safe to push down */
fpinfo->pushdown_safe = true;
/* Construct PgFdwPathExtraData */
fpextra = (PgFdwPathExtraData *) palloc0(sizeof(PgFdwPathExtraData));
fpextra->target = root->upper_targets[UPPERREL_FINAL];
fpextra->has_final_sort = has_final_sort;
fpextra->has_limit = extra->limit_needed;
fpextra->limit_tuples = extra->limit_tuples;
fpextra->count_est = extra->count_est;
fpextra->offset_est = extra->offset_est;
/*
* Estimate the costs of performing the final sort and the LIMIT
* restriction remotely. If has_final_sort is false, we wouldn't need to
* execute EXPLAIN anymore if use_remote_estimate, since the costs can be
* roughly estimated using the costs we already have for the underlying
* relation, in the same way as when use_remote_estimate is false. Since
* it's pretty expensive to execute EXPLAIN, force use_remote_estimate to
* false in that case.
*/
if (!fpextra->has_final_sort)
{
save_use_remote_estimate = ifpinfo->use_remote_estimate;
ifpinfo->use_remote_estimate = false;
}
estimate_path_cost_size(root, input_rel, NIL, pathkeys, fpextra,
&rows, &width, &startup_cost, &total_cost);
if (!fpextra->has_final_sort)
ifpinfo->use_remote_estimate = save_use_remote_estimate;
/*
* Build the fdw_private list that will be used by postgresGetForeignPlan.
* Items in the list must match order in enum FdwPathPrivateIndex.
*/
fdw_private = list_make2(makeInteger(has_final_sort),
makeInteger(extra->limit_needed));
/*
* Create foreign final path; this gets rid of a no-longer-needed outer
* plan (if any), which makes the EXPLAIN output look cleaner
*/
final_path = create_foreign_upper_path(root,
input_rel,
root->upper_targets[UPPERREL_FINAL],
rows,
startup_cost,
total_cost,
pathkeys,
NULL, /* no extra plan */
fdw_private);
/* and add it to the final_rel */
add_path(final_rel, (Path *) final_path);
}
/*
* Create a tuple from the specified row of the PGresult.
*
* rel is the local representation of the foreign table, attinmeta is
* conversion data for the rel's tupdesc, and retrieved_attrs is an
* integer list of the table column numbers present in the PGresult.
* temp_context is a working context that can be reset after each tuple.
*/
static HeapTuple
make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
List *retrieved_attrs,
ForeignScanState *fsstate,
MemoryContext temp_context)
{
HeapTuple tuple;
TupleDesc tupdesc;
Datum *values;
bool *nulls;
ItemPointer ctid = NULL;
ConversionLocation errpos;
ErrorContextCallback errcallback;
MemoryContext oldcontext;
ListCell *lc;
int j;
Assert(row < PQntuples(res));
/*
* Do the following work in a temp context that we reset after each tuple.
* This cleans up not only the data we have direct access to, but any
* cruft the I/O functions might leak.
*/
oldcontext = MemoryContextSwitchTo(temp_context);
if (rel)
tupdesc = RelationGetDescr(rel);
else
{
Assert(fsstate);
tupdesc = fsstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
}
values = (Datum *) palloc0(tupdesc->natts * sizeof(Datum));
nulls = (bool *) palloc(tupdesc->natts * sizeof(bool));
/* Initialize to nulls for any columns not present in result */
memset(nulls, true, tupdesc->natts * sizeof(bool));
/*
* Set up and install callback to report where conversion error occurs.
*/
errpos.rel = rel;
errpos.cur_attno = 0;
errpos.fsstate = fsstate;
errcallback.callback = conversion_error_callback;
errcallback.arg = (void *) &errpos;
errcallback.previous = error_context_stack;
error_context_stack = &errcallback;
/*
* i indexes columns in the relation, j indexes columns in the PGresult.
*/
j = 0;
foreach(lc, retrieved_attrs)
{
int i = lfirst_int(lc);
char *valstr;
/* fetch next column's textual value */
if (PQgetisnull(res, row, j))
valstr = NULL;
else
valstr = PQgetvalue(res, row, j);
/*
* convert value to internal representation
*
* Note: we ignore system columns other than ctid and oid in result
*/
errpos.cur_attno = i;
if (i > 0)
{
/* ordinary column */
Assert(i <= tupdesc->natts);
nulls[i - 1] = (valstr == NULL);
/* Apply the input function even to nulls, to support domains */
values[i - 1] = InputFunctionCall(&attinmeta->attinfuncs[i - 1],
valstr,
attinmeta->attioparams[i - 1],
attinmeta->atttypmods[i - 1]);
}
else if (i == SelfItemPointerAttributeNumber)
{
/* ctid */
if (valstr != NULL)
{
Datum datum;
datum = DirectFunctionCall1(tidin, CStringGetDatum(valstr));
ctid = (ItemPointer) DatumGetPointer(datum);
}
}
errpos.cur_attno = 0;
j++;
}
/* Uninstall error context callback. */
error_context_stack = errcallback.previous;
/*
* Check we got the expected number of columns. Note: j == 0 and
* PQnfields == 1 is expected, since deparse emits a NULL if no columns.
*/
if (j > 0 && j != PQnfields(res))
elog(ERROR, "remote query result does not match the foreign table");
/*
* Build the result tuple in caller's memory context.
*/
MemoryContextSwitchTo(oldcontext);
tuple = heap_form_tuple(tupdesc, values, nulls);
/*
* If we have a CTID to return, install it in both t_self and t_ctid.
* t_self is the normal place, but if the tuple is converted to a
* composite Datum, t_self will be lost; setting t_ctid allows CTID to be
* preserved during EvalPlanQual re-evaluations (see ROW_MARK_COPY code).
*/
if (ctid)
tuple->t_self = tuple->t_data->t_ctid = *ctid;
/*
* Stomp on the xmin, xmax, and cmin fields from the tuple created by
* heap_form_tuple. heap_form_tuple actually creates the tuple with
* DatumTupleFields, not HeapTupleFields, but the executor expects
* HeapTupleFields and will happily extract system columns on that
* assumption. If we don't do this then, for example, the tuple length
* ends up in the xmin field, which isn't what we want.
*/
HeapTupleHeaderSetXmax(tuple->t_data, InvalidTransactionId);
HeapTupleHeaderSetXmin(tuple->t_data, InvalidTransactionId);
HeapTupleHeaderSetCmin(tuple->t_data, InvalidTransactionId);
/* Clean up */
MemoryContextReset(temp_context);
return tuple;
}
/*
* Callback function which is called when error occurs during column value
* conversion. Print names of column and relation.
*/
static void
conversion_error_callback(void *arg)
{
const char *attname = NULL;
const char *relname = NULL;
bool is_wholerow = false;
ConversionLocation *errpos = (ConversionLocation *) arg;
if (errpos->rel)
{
/* error occurred in a scan against a foreign table */
TupleDesc tupdesc = RelationGetDescr(errpos->rel);
Form_pg_attribute attr = TupleDescAttr(tupdesc, errpos->cur_attno - 1);
if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts)
attname = NameStr(attr->attname);
else if (errpos->cur_attno == SelfItemPointerAttributeNumber)
attname = "ctid";
relname = RelationGetRelationName(errpos->rel);
}
else
{
/* error occurred in a scan against a foreign join */
ForeignScanState *fsstate = errpos->fsstate;
ForeignScan *fsplan = castNode(ForeignScan, fsstate->ss.ps.plan);
EState *estate = fsstate->ss.ps.state;
TargetEntry *tle;
tle = list_nth_node(TargetEntry, fsplan->fdw_scan_tlist,
errpos->cur_attno - 1);
/*
* Target list can have Vars and expressions. For Vars, we can get
* its relation, however for expressions we can't. Thus for
* expressions, just show generic context message.
*/
if (IsA(tle->expr, Var))
{
RangeTblEntry *rte;
Var *var = (Var *) tle->expr;
rte = exec_rt_fetch(var->varno, estate);
if (var->varattno == 0)
is_wholerow = true;
else
attname = get_attname(rte->relid, var->varattno, false);
relname = get_rel_name(rte->relid);
}
else
errcontext("processing expression at position %d in select list",
errpos->cur_attno);
}
if (relname)
{
if (is_wholerow)
errcontext("whole-row reference to foreign table \"%s\"", relname);
else if (attname)
errcontext("column \"%s\" of foreign table \"%s\"", attname, relname);
}
}
/*
* Find an equivalence class member expression, all of whose Vars, come from
* the indicated relation.
*/
Expr *
find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
{
ListCell *lc_em;
foreach(lc_em, ec->ec_members)
{
EquivalenceMember *em = lfirst(lc_em);
if (bms_is_subset(em->em_relids, rel->relids) &&
!bms_is_empty(em->em_relids))
{
/*
* If there is more than one equivalence member whose Vars are
* taken entirely from this relation, we'll be content to choose
* any one of those.
*/
return em->em_expr;
}
}
/* We didn't find any suitable equivalence class expression */
return NULL;
}
/*
* Find an equivalence class member expression to be computed as a sort column
* in the given target.
*/
Expr *
find_em_expr_for_input_target(PlannerInfo *root,
EquivalenceClass *ec,
PathTarget *target)
{
ListCell *lc1;
int i;
i = 0;
foreach(lc1, target->exprs)
{
Expr *expr = (Expr *) lfirst(lc1);
Index sgref = get_pathtarget_sortgroupref(target, i);
ListCell *lc2;
/* Ignore non-sort expressions */
if (sgref == 0 ||
get_sortgroupref_clause_noerr(sgref,
root->parse->sortClause) == NULL)
{
i++;
continue;
}
/* We ignore binary-compatible relabeling on both ends */
while (expr && IsA(expr, RelabelType))
expr = ((RelabelType *) expr)->arg;
/* Locate an EquivalenceClass member matching this expr, if any */
foreach(lc2, ec->ec_members)
{
EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
Expr *em_expr;
/* Don't match constants */
if (em->em_is_const)
continue;
/* Ignore child members */
if (em->em_is_child)
continue;
/* Match if same expression (after stripping relabel) */
em_expr = em->em_expr;
while (em_expr && IsA(em_expr, RelabelType))
em_expr = ((RelabelType *) em_expr)->arg;
if (equal(em_expr, expr))
return em->em_expr;
}
i++;
}
elog(ERROR, "could not find pathkey item to sort");
return NULL; /* keep compiler quiet */
}
static int
greenplumCheckIsGreenplum(UserMapping *user)
{
PGconn *conn;
PGresult *res;
int ret;
char *query = "SELECT version()";
conn = GetConnection(user, false);
res = pgfdw_exec_query(conn, query);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, true, query);
if (PQntuples(res) == 0)
pgfdw_report_error(ERROR, res, conn, true, query);
ret = strstr(PQgetvalue(res, 0, 0), "Greenplum Database") ? 1 : 0;
PQclear(res);
ReleaseConnection(conn);
return ret;
}
相关信息
相关文章
0
赞
热门推荐
-
2、 - 优质文章
-
3、 gate.io
-
6、 golang
-
7、 openharmony