greenplumn var 源码
greenplumn var 代码
文件路径：/src/backend/optimizer/util/var.c
/*-------------------------------------------------------------------------
*
* var.c
* Var node manipulation routines
*
* Note: for most purposes, PlaceHolderVar is considered a Var too,
* even if its contained expression is variable-free. Also, CurrentOfExpr
* is treated as a Var for purposes of determining whether an expression
* contains variables.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
* Portions Copyright (c) 2006-2008, Greenplum inc
* Portions Copyright (c) 2012-Present VMware, Inc. or its affiliates.
*
*
* IDENTIFICATION
* src/backend/optimizer/util/var.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/htup.h"
#include "access/sysattr.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "optimizer/prep.h"
#include "optimizer/walkers.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
typedef struct
{
Relids varnos;
int sublevels_up;
} pull_varnos_context;
typedef struct
{
Bitmapset *varattnos;
Index varno;
} pull_varattnos_context;
typedef struct
{
List *vars;
int sublevels_up;
} pull_vars_context;
typedef struct
{
int var_location;
int sublevels_up;
} locate_var_of_level_context;
typedef struct
{
List *varlist;
int flags;
} pull_var_clause_context;
typedef struct
{
Query *query; /* outer Query */
int sublevels_up;
bool possible_sublink; /* could aliases include a SubLink? */
bool inserted_sublink; /* have we inserted a SubLink? */
} flatten_join_alias_vars_context;
static bool pull_varnos_walker(Node *node,
pull_varnos_context *context);
static bool pull_varattnos_walker(Node *node, pull_varattnos_context *context);
static bool pull_vars_walker(Node *node, pull_vars_context *context);
static bool contain_var_clause_walker(Node *node, void *context);
static bool contain_vars_of_level_walker(Node *node, int *sublevels_up);
static bool locate_var_of_level_walker(Node *node,
locate_var_of_level_context *context);
static bool pull_var_clause_walker(Node *node,
pull_var_clause_context *context);
static Node *flatten_join_alias_vars_mutator(Node *node,
flatten_join_alias_vars_context *context);
static Relids alias_relid_set(Query *query, Relids relids);
/*
* cdb_walk_vars
* Invoke callback function on each Var and/or Aggref node in an expression.
* If a callback returns true, no further nodes are visited, and true is
* returned. Otherwise after visiting all nodes, false is returned.
*
* Will recurse into sublinks. Also, may be invoked directly on a Query.
*/
typedef bool (*Cdb_walk_vars_callback_Aggref)(Aggref *aggref, void *context, int sublevelsup);
typedef bool (*Cdb_walk_vars_callback_Var)(Var *var, void *context, int sublevelsup);
typedef bool (*Cdb_walk_vars_callback_CurrentOf)(CurrentOfExpr *expr, void *context, int sublevelsup);
typedef bool (*Cdb_walk_vars_callback_placeholdervar)(PlaceHolderVar *expr, void *context, int sublevelsup);
typedef struct Cdb_walk_vars_context
{
Cdb_walk_vars_callback_Var callback_var;
Cdb_walk_vars_callback_Aggref callback_aggref;
Cdb_walk_vars_callback_CurrentOf callback_currentof;
Cdb_walk_vars_callback_placeholdervar callback_placeholdervar;
void *context;
int sublevelsup;
} Cdb_walk_vars_context;
static bool
cdb_walk_vars_walker(Node *node, void *wvwcontext)
{
Cdb_walk_vars_context *ctx = (Cdb_walk_vars_context *)wvwcontext;
if (node == NULL)
return false;
if (IsA(node, Var) &&
ctx->callback_var != NULL)
return ctx->callback_var((Var *)node, ctx->context, ctx->sublevelsup);
if (IsA(node, Aggref) &&
ctx->callback_aggref != NULL)
return ctx->callback_aggref((Aggref *)node, ctx->context, ctx->sublevelsup);
if (IsA(node, CurrentOfExpr) &&
ctx->callback_currentof != NULL)
return ctx->callback_currentof((CurrentOfExpr *)node, ctx->context, ctx->sublevelsup);
if (IsA(node, PlaceHolderVar) &&
ctx->callback_placeholdervar != NULL)
return ctx->callback_placeholdervar((PlaceHolderVar *)node, ctx->context, ctx->sublevelsup);
if (IsA(node, Query))
{
bool b;
/* Recurse into subselects */
ctx->sublevelsup++;
b = query_tree_walker((Query *)node, cdb_walk_vars_walker, ctx, 0);
ctx->sublevelsup--;
return b;
}
return expression_tree_walker(node, cdb_walk_vars_walker, ctx);
} /* cdb_walk_vars_walker */
static bool
cdb_walk_vars(Node *node,
Cdb_walk_vars_callback_Var callback_var,
Cdb_walk_vars_callback_Aggref callback_aggref,
Cdb_walk_vars_callback_CurrentOf callback_currentof,
Cdb_walk_vars_callback_placeholdervar callback_placeholdervar,
void *context,
int levelsup)
{
Cdb_walk_vars_context ctx;
ctx.callback_var = callback_var;
ctx.callback_aggref = callback_aggref;
ctx.callback_currentof = callback_currentof;
ctx.callback_placeholdervar = callback_placeholdervar;
ctx.context = context;
ctx.sublevelsup = levelsup;
/*
* Must be prepared to start with a Query or a bare expression tree; if
* it's a Query, we don't want to increment levelsdown.
*/
return query_or_expression_tree_walker(node, cdb_walk_vars_walker, &ctx, 0);
} /* cdb_walk_vars */
/*
* pull_varnos
* Create a set of all the distinct varnos present in a parsetree.
* Only varnos that reference level-zero rtable entries are considered.
*
* NOTE: this is used on not-yet-planned expressions. It may therefore find
* bare SubLinks, and if so it needs to recurse into them to look for uplevel
* references to the desired rtable level! But when we find a completed
* SubPlan, we only need to look at the parameters passed to the subplan.
*/
Relids
pull_varnos(Node *node)
{
return pull_varnos_of_level(node, 0);
}
/*
* pull_varnos_of_level
* Create a set of all the distinct varnos present in a parsetree.
* Only Vars of the specified level are considered.
*/
Relids
pull_varnos_of_level(Node *node, int levelsup)
{
pull_varnos_context context;
context.varnos = NULL;
context.sublevels_up = levelsup;
/*
* Must be prepared to start with a Query or a bare expression tree; if
* it's a Query, we don't want to increment sublevels_up.
*/
query_or_expression_tree_walker(node,
pull_varnos_walker,
(void *) &context,
0);
return context.varnos;
}
static bool
pull_varnos_walker(Node *node, pull_varnos_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
Var *var = (Var *) node;
if (var->varlevelsup == context->sublevels_up)
context->varnos = bms_add_member(context->varnos, var->varno);
return false;
}
if (IsA(node, CurrentOfExpr))
{
CurrentOfExpr *cexpr = (CurrentOfExpr *) node;
if (context->sublevels_up == 0)
context->varnos = bms_add_member(context->varnos, cexpr->cvarno);
return false;
}
if (IsA(node, PlaceHolderVar))
{
/*
* A PlaceHolderVar acts as a variable of its syntactic scope, or
* lower than that if it references only a subset of the rels in its
* syntactic scope. It might also contain lateral references, but we
* should ignore such references when computing the set of varnos in
* an expression tree. Also, if the PHV contains no variables within
* its syntactic scope, it will be forced to be evaluated exactly at
* the syntactic scope, so take that as the relid set.
*/
PlaceHolderVar *phv = (PlaceHolderVar *) node;
pull_varnos_context subcontext;
subcontext.varnos = NULL;
subcontext.sublevels_up = context->sublevels_up;
(void) pull_varnos_walker((Node *) phv->phexpr, &subcontext);
if (phv->phlevelsup == context->sublevels_up)
{
subcontext.varnos = bms_int_members(subcontext.varnos,
phv->phrels);
if (bms_is_empty(subcontext.varnos))
context->varnos = bms_add_members(context->varnos,
phv->phrels);
}
context->varnos = bms_join(context->varnos, subcontext.varnos);
return false;
}
if (IsA(node, Query))
{
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
bool result;
context->sublevels_up++;
result = query_tree_walker((Query *) node, pull_varnos_walker,
(void *) context, 0);
context->sublevels_up--;
return result;
}
return expression_tree_walker(node, pull_varnos_walker,
(void *) context);
}
/*
* pull_varattnos
* Find all the distinct attribute numbers present in an expression tree,
* and add them to the initial contents of *varattnos.
* Only Vars of the given varno and rtable level zero are considered.
*
* Attribute numbers are offset by FirstLowInvalidHeapAttributeNumber so that
* we can include system attributes (e.g., OID) in the bitmap representation.
*
* Currently, this does not support unplanned subqueries; that is not needed
* for current uses. It will handle already-planned SubPlan nodes, though,
* looking into only the "testexpr" and the "args" list. (The subplan cannot
* contain any other references to Vars of the current level.)
*/
void
pull_varattnos(Node *node, Index varno, Bitmapset **varattnos)
{
pull_varattnos_context context;
context.varattnos = *varattnos;
context.varno = varno;
(void) pull_varattnos_walker(node, &context);
*varattnos = context.varattnos;
}
static bool
pull_varattnos_walker(Node *node, pull_varattnos_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
Var *var = (Var *) node;
if (var->varno == context->varno && var->varlevelsup == 0)
context->varattnos =
bms_add_member(context->varattnos,
var->varattno - FirstLowInvalidHeapAttributeNumber);
return false;
}
/* Should not find an unplanned subquery */
Assert(!IsA(node, Query));
return expression_tree_walker(node, pull_varattnos_walker,
(void *) context);
}
/*
* pull_vars_of_level
* Create a list of all Vars (and PlaceHolderVars) referencing the
* specified query level in the given parsetree.
*
* Caution: the Vars are not copied, only linked into the list.
*/
List *
pull_vars_of_level(Node *node, int levelsup)
{
pull_vars_context context;
context.vars = NIL;
context.sublevels_up = levelsup;
/*
* Must be prepared to start with a Query or a bare expression tree; if
* it's a Query, we don't want to increment sublevels_up.
*/
query_or_expression_tree_walker(node,
pull_vars_walker,
(void *) &context,
0);
return context.vars;
}
static bool
pull_vars_walker(Node *node, pull_vars_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
Var *var = (Var *) node;
if (var->varlevelsup == context->sublevels_up)
context->vars = lappend(context->vars, var);
return false;
}
if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
if (phv->phlevelsup == context->sublevels_up)
context->vars = lappend(context->vars, phv);
/* we don't want to look into the contained expression */
return false;
}
if (IsA(node, Query))
{
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
bool result;
context->sublevels_up++;
result = query_tree_walker((Query *) node, pull_vars_walker,
(void *) context, 0);
context->sublevels_up--;
return result;
}
return expression_tree_walker(node, pull_vars_walker,
(void *) context);
}
/*
* contain_var_clause
* Recursively scan a clause to discover whether it contains any Var nodes
* (of the current query level).
*
* Returns true if any varnode found.
*
* Does not examine subqueries, therefore must only be used after reduction
* of sublinks to subplans!
*/
bool
contain_var_clause(Node *node)
{
return contain_var_clause_walker(node, NULL);
}
static bool
contain_var_clause_walker(Node *node, void *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
if (((Var *) node)->varlevelsup == 0)
return true; /* abort the tree traversal and return true */
return false;
}
if (IsA(node, CurrentOfExpr))
return true;
if (IsA(node, PlaceHolderVar))
{
if (((PlaceHolderVar *) node)->phlevelsup == 0)
return true; /* abort the tree traversal and return true */
/* else fall through to check the contained expr */
}
return expression_tree_walker(node, contain_var_clause_walker, context);
}
/*
* contain_vars_of_level
* Recursively scan a clause to discover whether it contains any Var nodes
* of the specified query level.
*
* Returns true if any such Var found.
*
* Will recurse into sublinks. Also, may be invoked directly on a Query.
*/
bool
contain_vars_of_level(Node *node, int levelsup)
{
int sublevels_up = levelsup;
return query_or_expression_tree_walker(node,
contain_vars_of_level_walker,
(void *) &sublevels_up,
0);
}
static bool
contain_vars_of_level_walker(Node *node, int *sublevels_up)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
if (((Var *) node)->varlevelsup == *sublevels_up)
return true; /* abort tree traversal and return true */
return false;
}
if (IsA(node, CurrentOfExpr))
{
if (*sublevels_up == 0)
return true;
return false;
}
if (IsA(node, PlaceHolderVar))
{
if (((PlaceHolderVar *) node)->phlevelsup == *sublevels_up)
return true; /* abort the tree traversal and return true */
/* else fall through to check the contained expr */
}
if (IsA(node, Query))
{
/* Recurse into subselects */
bool result;
(*sublevels_up)++;
result = query_tree_walker((Query *) node,
contain_vars_of_level_walker,
(void *) sublevels_up,
0);
(*sublevels_up)--;
return result;
}
return expression_tree_walker(node,
contain_vars_of_level_walker,
(void *) sublevels_up);
}
/*
* locate_var_of_level
* Find the parse location of any Var of the specified query level.
*
* Returns -1 if no such Var is in the querytree, or if they all have
* unknown parse location. (The former case is probably caller error,
* but we don't bother to distinguish it from the latter case.)
*
* Will recurse into sublinks. Also, may be invoked directly on a Query.
*
* Note: it might seem appropriate to merge this functionality into
* contain_vars_of_level, but that would complicate that function's API.
* Currently, the only uses of this function are for error reporting,
* and so shaving cycles probably isn't very important.
*/
int
locate_var_of_level(Node *node, int levelsup)
{
locate_var_of_level_context context;
context.var_location = -1; /* in case we find nothing */
context.sublevels_up = levelsup;
(void) query_or_expression_tree_walker(node,
locate_var_of_level_walker,
(void *) &context,
0);
return context.var_location;
}
static bool
locate_var_of_level_walker(Node *node,
locate_var_of_level_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
Var *var = (Var *) node;
if (var->varlevelsup == context->sublevels_up &&
var->location >= 0)
{
context->var_location = var->location;
return true; /* abort tree traversal and return true */
}
return false;
}
if (IsA(node, CurrentOfExpr))
{
/* since CurrentOfExpr doesn't carry location, nothing we can do */
return false;
}
/* No extra code needed for PlaceHolderVar; just look in contained expr */
if (IsA(node, Query))
{
/* Recurse into subselects */
bool result;
context->sublevels_up++;
result = query_tree_walker((Query *) node,
locate_var_of_level_walker,
(void *) context,
0);
context->sublevels_up--;
return result;
}
return expression_tree_walker(node,
locate_var_of_level_walker,
(void *) context);
}
/*
* contain_vars_of_level_or_above
* Recursively scan a clause to discover whether it contains any Var or
* Aggref nodes of the specified query level or above. For example,
* pass 1 to detect all nonlocal Vars.
*
* Returns true if any such Var found.
*
* Will recurse into sublinks. Also, may be invoked directly on a Query.
*/
static bool
contain_vars_of_level_or_above_cbVar(Var *var, void *unused, int sublevelsup)
{
if ((int)var->varlevelsup >= sublevelsup)
return true; /* abort tree traversal and return true */
return false;
}
static bool
contain_vars_of_level_or_above_cbAggref(Aggref *aggref, void *unused, int sublevelsup)
{
if ((int)aggref->agglevelsup >= sublevelsup)
return true;
/* visit aggregate's args */
return cdb_walk_vars((Node *)aggref->args,
contain_vars_of_level_or_above_cbVar,
contain_vars_of_level_or_above_cbAggref,
NULL,
NULL,
NULL, // GPDB_84_MERGE_FIXME: Can arguments of Aggref contain PlaceHolderVars ?
sublevelsup);
}
static bool
contain_vars_of_level_or_above_cbPlaceHolderVar(PlaceHolderVar *placeholdervar, void *unused, int sublevelsup)
{
if(placeholdervar->phlevelsup >= sublevelsup)
return true;
/* visit placeholder's contained expression */
return cdb_walk_vars((Node*)placeholdervar->phexpr,
contain_vars_of_level_or_above_cbVar,
contain_vars_of_level_or_above_cbAggref,
NULL,
contain_vars_of_level_or_above_cbPlaceHolderVar,
NULL,
sublevelsup);
}
bool
contain_vars_of_level_or_above(Node *node, int levelsup)
{
return cdb_walk_vars(node,
contain_vars_of_level_or_above_cbVar,
contain_vars_of_level_or_above_cbAggref,
NULL,
contain_vars_of_level_or_above_cbPlaceHolderVar,
NULL,
levelsup);
}
/*
* pull_var_clause
* Recursively pulls all Var nodes from an expression clause.
*
* Aggrefs are handled according to these bits in 'flags':
* PVC_INCLUDE_AGGREGATES include Aggrefs in output list
* PVC_RECURSE_AGGREGATES recurse into Aggref arguments
* neither flag throw error if Aggref found
* Vars within an Aggref's expression are included in the result only
* when PVC_RECURSE_AGGREGATES is specified.
*
* WindowFuncs are handled according to these bits in 'flags':
* PVC_INCLUDE_WINDOWFUNCS include WindowFuncs in output list
* PVC_RECURSE_WINDOWFUNCS recurse into WindowFunc arguments
* neither flag throw error if WindowFunc found
* Vars within a WindowFunc's expression are included in the result only
* when PVC_RECURSE_WINDOWFUNCS is specified.
*
* PlaceHolderVars are handled according to these bits in 'flags':
* PVC_INCLUDE_PLACEHOLDERS include PlaceHolderVars in output list
* PVC_RECURSE_PLACEHOLDERS recurse into PlaceHolderVar arguments
* neither flag throw error if PlaceHolderVar found
* Vars within a PHV's expression are included in the result only
* when PVC_RECURSE_PLACEHOLDERS is specified.
*
* GroupingFuncs are treated mostly like Aggrefs, and so do not need
* their own flag bits.
*
* CurrentOfExpr nodes are ignored in all cases.
*
* Upper-level vars (with varlevelsup > 0) should not be seen here,
* likewise for upper-level Aggrefs and PlaceHolderVars.
*
* Returns list of nodes found. Note the nodes themselves are not
* copied, only referenced.
*
* Does not examine subqueries, therefore must only be used after reduction
* of sublinks to subplans!
*/
List *
pull_var_clause(Node *node, int flags)
{
pull_var_clause_context context;
/* Assert that caller has not specified inconsistent flags */
Assert((flags & (PVC_INCLUDE_AGGREGATES | PVC_RECURSE_AGGREGATES))
!= (PVC_INCLUDE_AGGREGATES | PVC_RECURSE_AGGREGATES));
Assert((flags & (PVC_INCLUDE_WINDOWFUNCS | PVC_RECURSE_WINDOWFUNCS))
!= (PVC_INCLUDE_WINDOWFUNCS | PVC_RECURSE_WINDOWFUNCS));
Assert((flags & (PVC_INCLUDE_PLACEHOLDERS | PVC_RECURSE_PLACEHOLDERS))
!= (PVC_INCLUDE_PLACEHOLDERS | PVC_RECURSE_PLACEHOLDERS));
context.varlist = NIL;
context.flags = flags;
pull_var_clause_walker(node, &context);
return context.varlist;
}
static bool
pull_var_clause_walker(Node *node, pull_var_clause_context *context)
{
if (node == NULL)
return false;
if (IsA(node, Var))
{
if (((Var *) node)->varlevelsup != 0)
elog(ERROR, "Upper-level Var found where not expected");
context->varlist = lappend(context->varlist, node);
return false;
}
else if (IsA(node, Aggref))
{
if (((Aggref *) node)->agglevelsup != 0)
elog(ERROR, "Upper-level Aggref found where not expected");
if (context->flags & PVC_INCLUDE_AGGREGATES)
{
context->varlist = lappend(context->varlist, node);
/* we do NOT descend into the contained expression */
return false;
}
else if (context->flags & PVC_RECURSE_AGGREGATES)
{
/* fall through to recurse into the aggregate's arguments */
}
else
elog(ERROR, "Aggref found where not expected");
}
else if (IsA(node, GroupingFunc))
{
if (((GroupingFunc *) node)->agglevelsup != 0)
elog(ERROR, "Upper-level GROUPING found where not expected");
if (context->flags & PVC_INCLUDE_AGGREGATES)
{
context->varlist = lappend(context->varlist, node);
/* we do NOT descend into the contained expression */
return false;
}
else if (context->flags & PVC_RECURSE_AGGREGATES)
{
/*
* We do NOT descend into the contained expression, even if the
* caller asked for it, because we never actually evaluate it -
* the result is driven entirely off the associated GROUP BY
* clause, so we never need to extract the actual Vars here.
*/
return false;
}
else
elog(ERROR, "GROUPING found where not expected");
}
else if (IsA(node, WindowFunc))
{
/* WindowFuncs have no levelsup field to check ... */
if (context->flags & PVC_INCLUDE_WINDOWFUNCS)
{
context->varlist = lappend(context->varlist, node);
/* we do NOT descend into the contained expressions */
return false;
}
else if (context->flags & PVC_RECURSE_WINDOWFUNCS)
{
/* fall through to recurse into the windowfunc's arguments */
}
else
elog(ERROR, "WindowFunc found where not expected");
}
else if (IsA(node, GroupId))
{
if (((GroupId *) node)->agglevelsup != 0)
elog(ERROR, "Upper-level GROUP_ID found where not expected");
if (context->flags & PVC_INCLUDE_AGGREGATES)
{
context->varlist = lappend(context->varlist, node);
/* we do NOT descend into the contained expression */
return false;
} else if (context->flags & PVC_RECURSE_AGGREGATES)
{
/*
* we do NOT descend into the contained expression,
* even if the caller asked for it, because we never
* actually evaluate it - the result is driven entirely
* off the associated GROUP BY clause, so we never need
* to extract the actual Vars here.
*/
return false;
}
else
elog(ERROR, "GROUP_ID found where not expected");
}
else if (IsA(node, PlaceHolderVar))
{
if (((PlaceHolderVar *) node)->phlevelsup != 0)
elog(ERROR, "Upper-level PlaceHolderVar found where not expected");
if (context->flags & PVC_INCLUDE_PLACEHOLDERS)
{
context->varlist = lappend(context->varlist, node);
/* we do NOT descend into the contained expression */
return false;
}
else if (context->flags & PVC_RECURSE_PLACEHOLDERS)
{
/* fall through to recurse into the placeholder's expression */
}
else
elog(ERROR, "PlaceHolderVar found where not expected");
}
return expression_tree_walker(node, pull_var_clause_walker,
(void *) context);
}
/*
* flatten_join_alias_vars
* Replace Vars that reference JOIN outputs with references to the original
* relation variables instead. This allows quals involving such vars to be
* pushed down. Whole-row Vars that reference JOIN relations are expanded
* into RowExpr constructs that name the individual output Vars. This
* is necessary since we will not scan the JOIN as a base relation, which
* is the only way that the executor can directly handle whole-row Vars.
*
* This also adjusts relid sets found in some expression node types to
* substitute the contained base rels for any join relid.
*
* If a JOIN contains sub-selects that have been flattened, its join alias
* entries might now be arbitrary expressions, not just Vars. This affects
* this function in one important way: we might find ourselves inserting
* SubLink expressions into subqueries, and we must make sure that their
* Query.hasSubLinks fields get set to true if so. If there are any
* SubLinks in the join alias lists, the outer Query should already have
* hasSubLinks = true, so this is only relevant to un-flattened subqueries.
*
* NOTE: this is used on not-yet-planned expressions. We do not expect it
* to be applied directly to the whole Query, so if we see a Query to start
* with, we do want to increment sublevels_up (this occurs for LATERAL
* subqueries).
*/
Node *
flatten_join_alias_vars(Query *query, Node *node)
{
flatten_join_alias_vars_context context;
context.query = query;
context.sublevels_up = 0;
/* flag whether join aliases could possibly contain SubLinks */
context.possible_sublink = query->hasSubLinks;
/* if hasSubLinks is already true, no need to work hard */
context.inserted_sublink = query->hasSubLinks;
return flatten_join_alias_vars_mutator(node, &context);
}
static Node *
flatten_join_alias_vars_mutator(Node *node,
flatten_join_alias_vars_context *context)
{
if (node == NULL)
return NULL;
if (IsA(node, Var))
{
Var *var = (Var *) node;
RangeTblEntry *rte;
Node *newvar;
/* No change unless Var belongs to a JOIN of the target level */
if (var->varlevelsup != context->sublevels_up)
return node; /* no need to copy, really */
rte = rt_fetch(var->varno, context->query->rtable);
if (rte->rtekind != RTE_JOIN)
return node;
if (var->varattno == InvalidAttrNumber)
{
/* Must expand whole-row reference */
RowExpr *rowexpr;
List *fields = NIL;
List *colnames = NIL;
AttrNumber attnum;
ListCell *lv;
ListCell *ln;
attnum = 0;
Assert(list_length(rte->joinaliasvars) == list_length(rte->eref->colnames));
forboth(lv, rte->joinaliasvars, ln, rte->eref->colnames)
{
newvar = (Node *) lfirst(lv);
attnum++;
/* Ignore dropped columns */
if (newvar == NULL)
continue;
newvar = copyObject(newvar);
/*
* If we are expanding an alias carried down from an upper
* query, must adjust its varlevelsup fields.
*/
if (context->sublevels_up != 0)
IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
/* Preserve original Var's location, if possible */
if (IsA(newvar, Var))
((Var *) newvar)->location = var->location;
/* Recurse in case join input is itself a join */
/* (also takes care of setting inserted_sublink if needed) */
newvar = flatten_join_alias_vars_mutator(newvar, context);
fields = lappend(fields, newvar);
/* We need the names of non-dropped columns, too */
colnames = lappend(colnames, copyObject((Node *) lfirst(ln)));
}
rowexpr = makeNode(RowExpr);
rowexpr->args = fields;
rowexpr->row_typeid = var->vartype;
rowexpr->row_format = COERCE_IMPLICIT_CAST;
rowexpr->colnames = colnames;
rowexpr->location = var->location;
return (Node *) rowexpr;
}
/* Expand join alias reference */
Assert(var->varattno > 0);
newvar = (Node *) list_nth(rte->joinaliasvars, var->varattno - 1);
Assert(newvar != NULL);
newvar = copyObject(newvar);
/*
* If we are expanding an alias carried down from an upper query, must
* adjust its varlevelsup fields.
*/
if (context->sublevels_up != 0)
IncrementVarSublevelsUp(newvar, context->sublevels_up, 0);
/* Preserve original Var's location, if possible */
if (IsA(newvar, Var))
((Var *) newvar)->location = var->location;
/* Recurse in case join input is itself a join */
newvar = flatten_join_alias_vars_mutator(newvar, context);
/* Detect if we are adding a sublink to query */
if (context->possible_sublink && !context->inserted_sublink)
context->inserted_sublink = checkExprHasSubLink(newvar);
return newvar;
}
if (IsA(node, PlaceHolderVar))
{
/* Copy the PlaceHolderVar node with correct mutation of subnodes */
PlaceHolderVar *phv;
phv = (PlaceHolderVar *) expression_tree_mutator(node,
flatten_join_alias_vars_mutator,
(void *) context);
/* now fix PlaceHolderVar's relid sets */
if (phv->phlevelsup == context->sublevels_up)
{
phv->phrels = alias_relid_set(context->query,
phv->phrels);
}
return (Node *) phv;
}
if (IsA(node, Query))
{
/* Recurse into RTE subquery or not-yet-planned sublink subquery */
Query *newnode;
bool save_inserted_sublink;
context->sublevels_up++;
save_inserted_sublink = context->inserted_sublink;
context->inserted_sublink = ((Query *) node)->hasSubLinks;
newnode = query_tree_mutator((Query *) node,
flatten_join_alias_vars_mutator,
(void *) context,
QTW_IGNORE_JOINALIASES);
newnode->hasSubLinks |= context->inserted_sublink;
context->inserted_sublink = save_inserted_sublink;
context->sublevels_up--;
return (Node *) newnode;
}
/* Already-planned tree not supported */
Assert(!IsA(node, SubPlan));
/* Shouldn't need to handle these planner auxiliary nodes here */
Assert(!IsA(node, SpecialJoinInfo));
Assert(!IsA(node, PlaceHolderInfo));
Assert(!IsA(node, MinMaxAggInfo));
return expression_tree_mutator(node, flatten_join_alias_vars_mutator,
(void *) context);
}
/*
* alias_relid_set: in a set of RT indexes, replace joins by their
* underlying base relids
*/
static Relids
alias_relid_set(Query *query, Relids relids)
{
Relids result = NULL;
int rtindex;
rtindex = -1;
while ((rtindex = bms_next_member(relids, rtindex)) >= 0)
{
RangeTblEntry *rte = rt_fetch(rtindex, query->rtable);
if (rte->rtekind == RTE_JOIN)
result = bms_join(result, get_relids_for_join(query, rtindex));
else
result = bms_add_member(result, rtindex);
}
return result;
}
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