greenplumn nodeSubplan 源码
greenplumn nodeSubplan 代码
文件路径：/src/backend/executor/nodeSubplan.c
/*-------------------------------------------------------------------------
*
* nodeSubplan.c
* routines to support sub-selects appearing in expressions
*
* This module is concerned with executing SubPlan expression nodes, which
* should not be confused with sub-SELECTs appearing in FROM. SubPlans are
* divided into "initplans", which are those that need only one evaluation per
* query (among other restrictions, this requires that they don't use any
* direct correlation variables from the parent plan level), and "regular"
* subplans, which are re-evaluated every time their result is required.
*
*
* Portions Copyright (c) 2005-2010, Greenplum inc
* Portions Copyright (c) 2012-Present VMware, Inc. or its affiliates.
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* src/backend/executor/nodeSubplan.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* ExecSubPlan - process a subselect
* ExecInitSubPlan - initialize a subselect
*/
#include "postgres.h"
#include <limits.h>
#include <math.h>
#include "access/htup_details.h"
#include "executor/executor.h"
#include "executor/nodeSubplan.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "miscadmin.h"
#include "utils/array.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "access/heapam.h"
#include "cdb/cdbdispatchresult.h"
#include "cdb/cdbexplain.h" /* cdbexplain_recvExecStats */
#include "cdb/cdbsubplan.h"
#include "cdb/cdbvars.h"
#include "cdb/cdbdisp.h"
#include "cdb/cdbdisp_query.h"
#include "cdb/ml_ipc.h"
#include "executor/nodeShareInputScan.h"
#include "pgstat.h"
static Datum ExecHashSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull);
static Datum ExecScanSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull);
static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
FmgrInfo *eqfunctions);
static bool slotAllNulls(TupleTableSlot *slot);
static bool slotNoNulls(TupleTableSlot *slot);
/* ----------------------------------------------------------------
* ExecSubPlan
*
* This is the main entry point for execution of a regular SubPlan.
* ----------------------------------------------------------------
*/
Datum
ExecSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull)
{
SubPlan *subplan = node->subplan;
EState *estate = node->planstate->state;
ScanDirection dir = estate->es_direction;
Datum retval;
CHECK_FOR_INTERRUPTS();
/* Set non-null as default */
*isNull = false;
/* Sanity checks */
if (subplan->subLinkType == CTE_SUBLINK)
elog(ERROR, "CTE subplans should not be executed via ExecSubPlan");
if (subplan->setParam != NIL && subplan->subLinkType != MULTIEXPR_SUBLINK)
elog(ERROR, "cannot set parent params from subquery");
/* Force forward-scan mode for evaluation */
estate->es_direction = ForwardScanDirection;
/* Select appropriate evaluation strategy */
if (subplan->useHashTable)
retval = ExecHashSubPlan(node, econtext, isNull);
else
retval = ExecScanSubPlan(node, econtext, isNull);
/* restore scan direction */
estate->es_direction = dir;
return retval;
}
/*
* ExecHashSubPlan: store subselect result in an in-memory hash table
*/
static Datum
ExecHashSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull)
{
SubPlan *subplan = node->subplan;
PlanState *planstate = node->planstate;
TupleTableSlot *slot;
/* Shouldn't have any direct correlation Vars */
if (subplan->parParam != NIL || node->args != NIL)
elog(ERROR, "hashed subplan with direct correlation not supported");
/*
* If first time through or we need to rescan the subplan, build the hash
* table.
*/
if (node->hashtable == NULL || planstate->chgParam != NULL)
buildSubPlanHash(node, econtext);
/*
* The result for an empty subplan is always FALSE; no need to evaluate
* lefthand side.
*/
*isNull = false;
if (!node->havehashrows && !node->havenullrows)
return BoolGetDatum(false);
/*
* Evaluate lefthand expressions and form a projection tuple. First we
* have to set the econtext to use (hack alert!).
*/
node->projLeft->pi_exprContext = econtext;
slot = ExecProject(node->projLeft);
/*
* Note: because we are typically called in a per-tuple context, we have
* to explicitly clear the projected tuple before returning. Otherwise,
* we'll have a double-free situation: the per-tuple context will probably
* be reset before we're called again, and then the tuple slot will think
* it still needs to free the tuple.
*/
/*
* If the LHS is all non-null, probe for an exact match in the main hash
* table. If we find one, the result is TRUE. Otherwise, scan the
* partly-null table to see if there are any rows that aren't provably
* unequal to the LHS; if so, the result is UNKNOWN. (We skip that part
* if we don't care about UNKNOWN.) Otherwise, the result is FALSE.
*
* Note: the reason we can avoid a full scan of the main hash table is
* that the combining operators are assumed never to yield NULL when both
* inputs are non-null. If they were to do so, we might need to produce
* UNKNOWN instead of FALSE because of an UNKNOWN result in comparing the
* LHS to some main-table entry --- which is a comparison we will not even
* make, unless there's a chance match of hash keys.
*/
if (slotNoNulls(slot))
{
if (node->havehashrows &&
FindTupleHashEntry(node->hashtable,
slot,
node->cur_eq_comp,
node->lhs_hash_funcs) != NULL)
{
ExecClearTuple(slot);
return BoolGetDatum(true);
}
if (node->havenullrows &&
findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
{
ExecClearTuple(slot);
*isNull = true;
return BoolGetDatum(false);
}
ExecClearTuple(slot);
return BoolGetDatum(false);
}
/*
* When the LHS is partly or wholly NULL, we can never return TRUE. If we
* don't care about UNKNOWN, just return FALSE. Otherwise, if the LHS is
* wholly NULL, immediately return UNKNOWN. (Since the combining
* operators are strict, the result could only be FALSE if the sub-select
* were empty, but we already handled that case.) Otherwise, we must scan
* both the main and partly-null tables to see if there are any rows that
* aren't provably unequal to the LHS; if so, the result is UNKNOWN.
* Otherwise, the result is FALSE.
*/
if (node->hashnulls == NULL)
{
ExecClearTuple(slot);
return BoolGetDatum(false);
}
if (slotAllNulls(slot))
{
ExecClearTuple(slot);
*isNull = true;
return BoolGetDatum(false);
}
/* Scan partly-null table first, since more likely to get a match */
if (node->havenullrows &&
findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
{
ExecClearTuple(slot);
*isNull = true;
return BoolGetDatum(false);
}
if (node->havehashrows &&
findPartialMatch(node->hashtable, slot, node->cur_eq_funcs))
{
ExecClearTuple(slot);
*isNull = true;
return BoolGetDatum(false);
}
ExecClearTuple(slot);
return BoolGetDatum(false);
}
/*
* ExecScanSubPlan: default case where we have to rescan subplan each time
*/
static Datum
ExecScanSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull)
{
SubPlan *subplan = node->subplan;
PlanState *planstate = node->planstate;
SubLinkType subLinkType = subplan->subLinkType;
MemoryContext oldcontext;
TupleTableSlot *slot;
Datum result;
bool found = false; /* true if got at least one subplan tuple */
ListCell *pvar;
ListCell *l;
ArrayBuildStateAny *astate = NULL;
/*
* MULTIEXPR subplans, when "executed", just return NULL; but first we
* mark the subplan's output parameters as needing recalculation. (This
* is a bit of a hack: it relies on the subplan appearing later in its
* targetlist than any of the referencing Params, so that all the Params
* have been evaluated before we re-mark them for the next evaluation
* cycle. But in general resjunk tlist items appear after non-resjunk
* ones, so this should be safe.) Unlike ExecReScanSetParamPlan, we do
* *not* set bits in the parent plan node's chgParam, because we don't
* want to cause a rescan of the parent.
*/
if (subLinkType == MULTIEXPR_SUBLINK)
{
EState *estate = node->parent->state;
foreach(l, subplan->setParam)
{
int paramid = lfirst_int(l);
ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
prm->execPlan = node;
}
*isNull = true;
return (Datum) 0;
}
/* Initialize ArrayBuildStateAny in caller's context, if needed */
if (subLinkType == ARRAY_SUBLINK)
astate = initArrayResultAny(subplan->firstColType,
CurrentMemoryContext, true);
/*
* We are probably in a short-lived expression-evaluation context. Switch
* to the per-query context for manipulating the child plan's chgParam,
* calling ExecProcNode on it, etc.
*/
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
/*
* Set Params of this plan from parent plan correlation values. (Any
* calculation we have to do is done in the parent econtext, since the
* Param values don't need to have per-query lifetime.)
*/
Assert(list_length(subplan->parParam) == list_length(node->args));
forboth(l, subplan->parParam, pvar, node->args)
{
int paramid = lfirst_int(l);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
econtext,
&(prm->isnull));
planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
}
/*
* Now that we've set up its parameters, we can reset the subplan.
*/
ExecReScan(planstate);
/*
* For all sublink types except EXPR_SUBLINK and ARRAY_SUBLINK, the result
* is boolean as are the results of the combining operators. We combine
* results across tuples (if the subplan produces more than one) using OR
* semantics for ANY_SUBLINK or AND semantics for ALL_SUBLINK.
* (ROWCOMPARE_SUBLINK doesn't allow multiple tuples from the subplan.)
* NULL results from the combining operators are handled according to the
* usual SQL semantics for OR and AND. The result for no input tuples is
* FALSE for ANY_SUBLINK, TRUE for {ALL_SUBLINK, NOT_EXISTS_SUBLINK}, NULL for
* ROWCOMPARE_SUBLINK.
*
* For EXPR_SUBLINK we require the subplan to produce no more than one
* tuple, else an error is raised. If zero tuples are produced, we return
* NULL. Assuming we get a tuple, we just use its first column (there can
* be only one non-junk column in this case).
*
* For ARRAY_SUBLINK we allow the subplan to produce any number of tuples,
* and form an array of the first column's values. Note in particular
* that we produce a zero-element array if no tuples are produced (this is
* a change from pre-8.3 behavior of returning NULL).
*/
result = BoolGetDatum(subLinkType == ALL_SUBLINK || subLinkType == NOT_EXISTS_SUBLINK);
*isNull = false;
for (slot = ExecProcNode(planstate);
!TupIsNull(slot);
slot = ExecProcNode(planstate))
{
TupleDesc tdesc = slot->tts_tupleDescriptor;
Datum rowresult;
bool rownull;
int col;
ListCell *plst;
if (subLinkType == EXISTS_SUBLINK || subLinkType == NOT_EXISTS_SUBLINK)
{
found = true;
bool val = true;
if (subLinkType == NOT_EXISTS_SUBLINK)
{
val = false;
}
result = BoolGetDatum(val);
break;
}
if (subLinkType == EXPR_SUBLINK)
{
/* cannot allow multiple input tuples for EXPR sublink */
if (found)
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
errmsg("more than one row returned by a subquery used as an expression")));
found = true;
/*
* We need to copy the subplan's tuple in case the result is of
* pass-by-ref type --- our return value will point into this
* copied tuple! Can't use the subplan's instance of the tuple
* since it won't still be valid after next ExecProcNode() call.
* node->curTuple keeps track of the copied tuple for eventual
* freeing.
*/
if (node->curTuple)
heap_freetuple(node->curTuple);
node->curTuple = ExecCopySlotHeapTuple(slot);
MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
result = heap_getattr(node->curTuple, 1, tdesc, isNull);
/* keep scanning subplan to make sure there's only one tuple */
continue;
}
if (subLinkType == ARRAY_SUBLINK)
{
Datum dvalue;
bool disnull;
found = true;
/* stash away current value */
Assert(subplan->firstColType == TupleDescAttr(tdesc, 0)->atttypid);
dvalue = slot_getattr(slot, 1, &disnull);
astate = accumArrayResultAny(astate, dvalue, disnull,
subplan->firstColType, oldcontext);
/* keep scanning subplan to collect all values */
continue;
}
/* cannot allow multiple input tuples for ROWCOMPARE sublink either */
if (subLinkType == ROWCOMPARE_SUBLINK && found)
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
errmsg("more than one row returned by a subquery used as an expression")));
found = true;
/*
* For ALL, ANY, and ROWCOMPARE sublinks, load up the Params
* representing the columns of the sub-select, and then evaluate the
* combining expression.
*/
col = 1;
foreach(plst, subplan->paramIds)
{
int paramid = lfirst_int(plst);
ParamExecData *prmdata;
prmdata = &(econtext->ecxt_param_exec_vals[paramid]);
Assert(prmdata->execPlan == NULL);
prmdata->value = slot_getattr(slot, col, &(prmdata->isnull));
col++;
}
rowresult = ExecEvalExprSwitchContext(node->testexpr, econtext,
&rownull);
if (subLinkType == ANY_SUBLINK)
{
/* combine across rows per OR semantics */
if (rownull)
*isNull = true;
else if (DatumGetBool(rowresult))
{
result = BoolGetDatum(true);
*isNull = false;
break; /* needn't look at any more rows */
}
}
else if (subLinkType == ALL_SUBLINK)
{
/* combine across rows per AND semantics */
if (rownull)
*isNull = true;
else if (!DatumGetBool(rowresult))
{
result = BoolGetDatum(false);
*isNull = false;
break; /* needn't look at any more rows */
}
}
else
{
/* must be ROWCOMPARE_SUBLINK */
result = rowresult;
*isNull = rownull;
}
}
MemoryContextSwitchTo(oldcontext);
if (subLinkType == ARRAY_SUBLINK)
{
/* We return the result in the caller's context */
result = makeArrayResultAny(astate, oldcontext, true);
}
else if (!found)
{
/*
* deal with empty subplan result. result/isNull were previously
* initialized correctly for all sublink types except EXPR and
* ROWCOMPARE; for those, return NULL.
*/
if (subLinkType == EXPR_SUBLINK ||
subLinkType == ROWCOMPARE_SUBLINK)
{
result = (Datum) 0;
*isNull = true;
}
}
return result;
}
/*
* buildSubPlanHash: load hash table by scanning subplan output.
*/
static void
buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
{
SubPlan *subplan = node->subplan;
PlanState *planstate = node->planstate;
int ncols = list_length(subplan->paramIds);
ExprContext *innerecontext = node->innerecontext;
MemoryContext oldcontext;
long nbuckets;
TupleTableSlot *slot;
Assert(subplan->subLinkType == ANY_SUBLINK);
/*
* If we already had any hash tables, reset 'em; otherwise create empty
* hash table(s).
*
* If we need to distinguish accurately between FALSE and UNKNOWN (i.e.,
* NULL) results of the IN operation, then we have to store subplan output
* rows that are partly or wholly NULL. We store such rows in a separate
* hash table that we expect will be much smaller than the main table. (We
* can use hashing to eliminate partly-null rows that are not distinct. We
* keep them separate to minimize the cost of the inevitable full-table
* searches; see findPartialMatch.)
*
* If it's not necessary to distinguish FALSE and UNKNOWN, then we don't
* need to store subplan output rows that contain NULL.
*/
MemoryContextReset(node->hashtablecxt);
node->hashtable = NULL;
node->hashnulls = NULL;
node->havehashrows = false;
node->havenullrows = false;
nbuckets = (long) Min(planstate->plan->plan_rows, (double) LONG_MAX);
if (nbuckets < 1)
nbuckets = 1;
if (node->hashtable)
ResetTupleHashTable(node->hashtable);
else
node->hashtable = BuildTupleHashTableExt(node->parent,
node->descRight,
ncols,
node->keyColIdx,
node->tab_eq_funcoids,
node->tab_hash_funcs,
node->tab_collations,
nbuckets,
0,
node->planstate->state->es_query_cxt,
node->hashtablecxt,
node->hashtempcxt,
false);
if (!subplan->unknownEqFalse)
{
if (ncols == 1)
nbuckets = 1; /* there can only be one entry */
else
{
nbuckets /= 16;
if (nbuckets < 1)
nbuckets = 1;
}
if (node->hashnulls)
ResetTupleHashTable(node->hashtable);
else
node->hashnulls = BuildTupleHashTableExt(node->parent,
node->descRight,
ncols,
node->keyColIdx,
node->tab_eq_funcoids,
node->tab_hash_funcs,
node->tab_collations,
nbuckets,
0,
node->planstate->state->es_query_cxt,
node->hashtablecxt,
node->hashtempcxt,
false);
}
/*
* We are probably in a short-lived expression-evaluation context. Switch
* to the per-query context for manipulating the child plan.
*/
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
/*
* Reset subplan to start.
*/
ExecReScan(planstate);
/*
* Scan the subplan and load the hash table(s). Note that when there are
* duplicate rows coming out of the sub-select, only one copy is stored.
*/
for (slot = ExecProcNode(planstate);
!TupIsNull(slot);
slot = ExecProcNode(planstate))
{
int col = 1;
ListCell *plst;
bool isnew;
/*
* Load up the Params representing the raw sub-select outputs, then
* form the projection tuple to store in the hashtable.
*/
foreach(plst, subplan->paramIds)
{
int paramid = lfirst_int(plst);
ParamExecData *prmdata;
prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
Assert(prmdata->execPlan == NULL);
prmdata->value = slot_getattr(slot, col,
&(prmdata->isnull));
col++;
}
slot = ExecProject(node->projRight);
/*
* If result contains any nulls, store separately or not at all.
*/
if (slotNoNulls(slot))
{
(void) LookupTupleHashEntry(node->hashtable, slot, &isnew);
node->havehashrows = true;
}
else if (node->hashnulls)
{
(void) LookupTupleHashEntry(node->hashnulls, slot, &isnew);
node->havenullrows = true;
}
/*
* Reset innerecontext after each inner tuple to free any memory used
* during ExecProject.
*/
ResetExprContext(innerecontext);
}
/*
* Since the projected tuples are in the sub-query's context and not the
* main context, we'd better clear the tuple slot before there's any
* chance of a reset of the sub-query's context. Else we will have the
* potential for a double free attempt. (XXX possibly no longer needed,
* but can't hurt.)
*/
ExecClearTuple(node->projRight->pi_state.resultslot);
MemoryContextSwitchTo(oldcontext);
}
/*
* execTuplesUnequal
* Return true if two tuples are definitely unequal in the indicated
* fields.
*
* Nulls are neither equal nor unequal to anything else. A true result
* is obtained only if there are non-null fields that compare not-equal.
*
* slot1, slot2: the tuples to compare (must have same columns!)
* numCols: the number of attributes to be examined
* matchColIdx: array of attribute column numbers
* eqFunctions: array of fmgr lookup info for the equality functions to use
* evalContext: short-term memory context for executing the functions
*/
static bool
execTuplesUnequal(TupleTableSlot *slot1,
TupleTableSlot *slot2,
int numCols,
AttrNumber *matchColIdx,
FmgrInfo *eqfunctions,
const Oid *collations,
MemoryContext evalContext)
{
MemoryContext oldContext;
bool result;
int i;
/* Reset and switch into the temp context. */
MemoryContextReset(evalContext);
oldContext = MemoryContextSwitchTo(evalContext);
/*
* We cannot report a match without checking all the fields, but we can
* report a non-match as soon as we find unequal fields. So, start
* comparing at the last field (least significant sort key). That's the
* most likely to be different if we are dealing with sorted input.
*/
result = false;
for (i = numCols; --i >= 0;)
{
AttrNumber att = matchColIdx[i];
Datum attr1,
attr2;
bool isNull1,
isNull2;
attr1 = slot_getattr(slot1, att, &isNull1);
if (isNull1)
continue; /* can't prove anything here */
attr2 = slot_getattr(slot2, att, &isNull2);
if (isNull2)
continue; /* can't prove anything here */
/* Apply the type-specific equality function */
if (!DatumGetBool(FunctionCall2Coll(&eqfunctions[i],
collations[i],
attr1, attr2)))
{
result = true; /* they are unequal */
break;
}
}
MemoryContextSwitchTo(oldContext);
return result;
}
/*
* findPartialMatch: does the hashtable contain an entry that is not
* provably distinct from the tuple?
*
* We have to scan the whole hashtable; we can't usefully use hashkeys
* to guide probing, since we might get partial matches on tuples with
* hashkeys quite unrelated to what we'd get from the given tuple.
*
* Caller must provide the equality functions to use, since in cross-type
* cases these are different from the hashtable's internal functions.
*/
static bool
findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
FmgrInfo *eqfunctions)
{
int numCols = hashtable->numCols;
AttrNumber *keyColIdx = hashtable->keyColIdx;
TupleHashIterator hashiter;
TupleHashEntry entry;
InitTupleHashIterator(hashtable, &hashiter);
while ((entry = ScanTupleHashTable(hashtable, &hashiter)) != NULL)
{
CHECK_FOR_INTERRUPTS();
ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
if (!execTuplesUnequal(slot, hashtable->tableslot,
numCols, keyColIdx,
eqfunctions,
hashtable->tab_collations,
hashtable->tempcxt))
{
TermTupleHashIterator(&hashiter);
return true;
}
}
/* No TermTupleHashIterator call needed here */
return false;
}
/*
* slotAllNulls: is the slot completely NULL?
*
* This does not test for dropped columns, which is OK because we only
* use it on projected tuples.
*/
static bool
slotAllNulls(TupleTableSlot *slot)
{
int ncols = slot->tts_tupleDescriptor->natts;
int i;
for (i = 1; i <= ncols; i++)
{
if (!slot_attisnull(slot, i))
return false;
}
return true;
}
/*
* slotNoNulls: is the slot entirely not NULL?
*
* This does not test for dropped columns, which is OK because we only
* use it on projected tuples.
*/
static bool
slotNoNulls(TupleTableSlot *slot)
{
int ncols = slot->tts_tupleDescriptor->natts;
int i;
for (i = 1; i <= ncols; i++)
{
if (slot_attisnull(slot, i))
return false;
}
return true;
}
/* ----------------------------------------------------------------
* ExecInitSubPlan
*
* Create a SubPlanState for a SubPlan; this is the SubPlan-specific part
* of ExecInitExpr(). We split it out so that it can be used for InitPlans
* as well as regular SubPlans. Note that we don't link the SubPlan into
* the parent's subPlan list, because that shouldn't happen for InitPlans.
* Instead, ExecInitExpr() does that one part.
* ----------------------------------------------------------------
*/
SubPlanState *
ExecInitSubPlan(SubPlan *subplan, PlanState *parent)
{
SubPlanState *sstate = makeNode(SubPlanState);
EState *estate = parent->state;
sstate->subplan = subplan;
/* Link the SubPlanState to already-initialized subplan */
sstate->planstate = (PlanState *) list_nth(estate->es_subplanstates,
subplan->plan_id - 1);
/* ... and to its parent's state */
sstate->parent = parent;
/* Initialize subexpressions */
sstate->testexpr = ExecInitExpr((Expr *) subplan->testexpr, parent);
sstate->args = ExecInitExprList(subplan->args, parent);
/*
* initialize my state
*/
sstate->curTuple = NULL;
sstate->curArray = PointerGetDatum(NULL);
sstate->projLeft = NULL;
sstate->projRight = NULL;
sstate->hashtable = NULL;
sstate->hashnulls = NULL;
sstate->hashtablecxt = NULL;
sstate->hashtempcxt = NULL;
sstate->innerecontext = NULL;
sstate->keyColIdx = NULL;
sstate->tab_eq_funcoids = NULL;
sstate->tab_hash_funcs = NULL;
sstate->tab_eq_funcs = NULL;
sstate->tab_collations = NULL;
sstate->lhs_hash_funcs = NULL;
sstate->cur_eq_funcs = NULL;
sstate->ts_state = NULL;
/*
* If this is an initplan or MULTIEXPR subplan, it has output parameters
* that the parent plan will use, so mark those parameters as needing
* evaluation. We don't actually run the subplan until we first need one
* of its outputs.
*
* A CTE subplan's output parameter is never to be evaluated in the normal
* way, so skip this in that case.
*
* Note that we don't set parent->chgParam here: the parent plan hasn't
* been run yet, so no need to force it to re-run.
*/
if (subplan->setParam != NIL && subplan->subLinkType != CTE_SUBLINK)
{
ListCell *lst;
foreach(lst, subplan->setParam)
{
int paramid = lfirst_int(lst);
ParamExecData *prmExec = &(estate->es_param_exec_vals[paramid]);
/**
* If we need to evaluate a parameter, save the planstate to do so.
*/
if ((Gp_role != GP_ROLE_EXECUTE || !subplan->is_initplan ||
estate->es_sliceTable == NULL))
{
prmExec->execPlan = sstate;
}
}
}
/*
* If we are going to hash the subquery output, initialize relevant stuff.
* (We don't create the hashtable until needed, though.)
*/
if (subplan->useHashTable)
{
int ncols,
i;
TupleDesc tupDescLeft;
TupleDesc tupDescRight;
TupleTableSlot *slot;
List *oplist,
*lefttlist,
*righttlist;
ListCell *l;
/* We need a memory context to hold the hash table(s) */
sstate->hashtablecxt =
AllocSetContextCreate(CurrentMemoryContext,
"Subplan HashTable Context",
ALLOCSET_DEFAULT_SIZES);
/* and a small one for the hash tables to use as temp storage */
sstate->hashtempcxt =
AllocSetContextCreate(CurrentMemoryContext,
"Subplan HashTable Temp Context",
ALLOCSET_SMALL_SIZES);
/* and a short-lived exprcontext for function evaluation */
sstate->innerecontext = CreateExprContext(estate);
/* Silly little array of column numbers 1..n */
ncols = list_length(subplan->paramIds);
sstate->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
for (i = 0; i < ncols; i++)
sstate->keyColIdx[i] = i + 1;
/*
* We use ExecProject to evaluate the lefthand and righthand
* expression lists and form tuples. (You might think that we could
* use the sub-select's output tuples directly, but that is not the
* case if we had to insert any run-time coercions of the sub-select's
* output datatypes; anyway this avoids storing any resjunk columns
* that might be in the sub-select's output.) Run through the
* combining expressions to build tlists for the lefthand and
* righthand sides.
*
* We also extract the combining operators themselves to initialize
* the equality and hashing functions for the hash tables.
*/
if (IsA(subplan->testexpr, OpExpr))
{
/* single combining operator */
oplist = list_make1(subplan->testexpr);
}
else if (is_andclause(subplan->testexpr))
{
/* multiple combining operators */
oplist = castNode(BoolExpr, subplan->testexpr)->args;
}
else
{
/* shouldn't see anything else in a hashable subplan */
elog(ERROR, "unrecognized testexpr type: %d",
(int) nodeTag(subplan->testexpr));
oplist = NIL; /* keep compiler quiet */
}
Assert(list_length(oplist) == ncols);
lefttlist = righttlist = NIL;
sstate->tab_eq_funcoids = (Oid *) palloc(ncols * sizeof(Oid));
sstate->tab_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
sstate->tab_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
sstate->tab_collations = (Oid *) palloc(ncols * sizeof(Oid));
sstate->lhs_hash_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
sstate->cur_eq_funcs = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
i = 1;
foreach(l, oplist)
{
OpExpr *opexpr = lfirst_node(OpExpr, l);
Expr *expr;
TargetEntry *tle;
Oid rhs_eq_oper;
Oid left_hashfn;
Oid right_hashfn;
Assert(list_length(opexpr->args) == 2);
/* Process lefthand argument */
expr = (Expr *) linitial(opexpr->args);
tle = makeTargetEntry(expr,
i,
NULL,
false);
lefttlist = lappend(lefttlist, tle);
/* Process righthand argument */
expr = (Expr *) lsecond(opexpr->args);
tle = makeTargetEntry(expr,
i,
NULL,
false);
righttlist = lappend(righttlist, tle);
/* Lookup the equality function (potentially cross-type) */
sstate->tab_eq_funcoids[i - 1] = opexpr->opfuncid;
fmgr_info(opexpr->opfuncid, &sstate->cur_eq_funcs[i - 1]);
fmgr_info_set_expr((Node *) opexpr, &sstate->cur_eq_funcs[i - 1]);
/* Look up the equality function for the RHS type */
if (!get_compatible_hash_operators(opexpr->opno,
NULL, &rhs_eq_oper))
elog(ERROR, "could not find compatible hash operator for operator %u",
opexpr->opno);
fmgr_info(get_opcode(rhs_eq_oper), &sstate->tab_eq_funcs[i - 1]);
/* Lookup the associated hash functions */
if (!get_op_hash_functions(opexpr->opno,
&left_hashfn, &right_hashfn))
elog(ERROR, "could not find hash function for hash operator %u",
opexpr->opno);
fmgr_info(left_hashfn, &sstate->lhs_hash_funcs[i - 1]);
fmgr_info(right_hashfn, &sstate->tab_hash_funcs[i - 1]);
/* Set collation */
sstate->tab_collations[i - 1] = opexpr->inputcollid;
i++;
}
/*
* Construct tupdescs, slots and projection nodes for left and right
* sides. The lefthand expressions will be evaluated in the parent
* plan node's exprcontext, which we don't have access to here.
* Fortunately we can just pass NULL for now and fill it in later
* (hack alert!). The righthand expressions will be evaluated in our
* own innerecontext.
*/
tupDescLeft = ExecTypeFromTL(lefttlist);
slot = ExecInitExtraTupleSlot(estate, tupDescLeft, &TTSOpsVirtual);
sstate->projLeft = ExecBuildProjectionInfo(lefttlist,
NULL,
slot,
parent,
NULL);
sstate->descRight = tupDescRight = ExecTypeFromTL(righttlist);
slot = ExecInitExtraTupleSlot(estate, tupDescRight, &TTSOpsVirtual);
sstate->projRight = ExecBuildProjectionInfo(righttlist,
sstate->innerecontext,
slot,
sstate->planstate,
NULL);
/*
* Create comparator for lookups of rows in the table (potentially
* across-type comparison).
*/
sstate->cur_eq_comp = ExecBuildGroupingEqual(tupDescLeft, tupDescRight,
&TTSOpsVirtual, &TTSOpsMinimalTuple,
ncols,
sstate->keyColIdx,
sstate->tab_eq_funcoids,
sstate->tab_collations,
parent);
}
return sstate;
}
/* ----------------------------------------------------------------
* ExecSetParamPlan
*
* Executes a subplan and sets its output parameters.
*
* This is called from ExecEvalParamExec() when the value of a PARAM_EXEC
* parameter is requested and the param's execPlan field is set (indicating
* that the param has not yet been evaluated). This allows lazy evaluation
* of initplans: we don't run the subplan until/unless we need its output.
* Note that this routine MUST clear the execPlan fields of the plan's
* output parameters after evaluating them!
*
* The results of this function are stored in the EState associated with the
* ExprContext (particularly, its ecxt_param_exec_vals); any pass-by-ref
* result Datums are allocated in the EState's per-query memory. The passed
* econtext can be any ExprContext belonging to that EState; which one is
* important only to the extent that the ExprContext's per-tuple memory
* context is used to evaluate any parameters passed down to the subplan.
* (Thus in principle, the shorter-lived the ExprContext the better, since
* that data isn't needed after we return. In practice, because initplan
* parameters are never more complex than Vars, Aggrefs, etc, evaluating them
* currently never leaks any memory anyway.)
* ----------------------------------------------------------------
*/
/*
* Greenplum Database Changes:
* In the case where this is running on the dispatcher, and it's a parallel
* dispatch subplan, we need to dispatch the query to the qExecs as well, like
* in ExecutorRun. Except in this case we don't have to worry about insert
* statements.
*/
void
ExecSetParamPlan(SubPlanState *node, ExprContext *econtext, QueryDesc *queryDesc)
{
SubPlan *subplan = node->subplan;
PlanState *planstate = node->planstate;
SubLinkType subLinkType = subplan->subLinkType;
EState *estate = planstate->state;
ScanDirection dir = estate->es_direction;
MemoryContext oldcontext = NULL;
TupleTableSlot *slot;
ListCell *pvar;
ListCell *l;
bool found = false;
ArrayBuildState *astate pg_attribute_unused() = NULL;
Size savepeakspace = MemoryContextGetPeakSpace(planstate->state->es_query_cxt);
bool needDtx;
bool shouldDispatch = false;
volatile bool explainRecvStats = false;
if (Gp_role == GP_ROLE_DISPATCH &&
planstate != NULL &&
planstate->plan != NULL &&
queryDesc)
{
int subsliceIndex = queryDesc->plannedstmt->subplan_sliceIds[subplan->plan_id - 1];
ExecSlice *subslice;
subslice = &estate->es_sliceTable->slices[subsliceIndex];
if (subslice->gangType != GANGTYPE_UNALLOCATED || subslice->children)
shouldDispatch = true;
}
/*
* Reset memory high-water mark so EXPLAIN ANALYZE can report each
* root slice's usage separately.
*/
MemoryContextSetPeakSpace(planstate->state->es_query_cxt, 0);
/*
* Need a try/catch block here so that if an ereport is called from
* within ExecutePlan, we can clean up by calling cdbdisp_checkDispatchResult.
* This cleans up the asynchronous commands running through the threads launched from
* CdbDispatchCommand.
*/
PG_TRY();
{
if (shouldDispatch)
{
needDtx = isCurrentDtxActivated();
/*
* This call returns after launching the threads that send the
* command to the appropriate segdbs. It does not wait for them
* to finish unless an error is detected before all are dispatched.
*/
CdbDispatchPlan(queryDesc,
estate->es_param_exec_vals,
needDtx, true);
/*
* Set up the interconnect for execution of the initplan root slice.
*/
Assert(!(queryDesc->estate->interconnect_context));
SetupInterconnect(queryDesc->estate);
Assert((queryDesc->estate->interconnect_context));
UpdateMotionExpectedReceivers(queryDesc->estate->motionlayer_context, queryDesc->estate->es_sliceTable);
}
ArrayBuildStateAny *astate = NULL;
if (subLinkType == ANY_SUBLINK ||
subLinkType == ALL_SUBLINK)
elog(ERROR, "ANY/ALL subselect unsupported as initplan");
if (subLinkType == CTE_SUBLINK)
elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
/*
* Enforce forward scan direction regardless of caller. It's hard but not
* impossible to get here in backward scan, so make it work anyway.
*/
estate->es_direction = ForwardScanDirection;
/* Initialize ArrayBuildStateAny in caller's context, if needed */
if (subLinkType == ARRAY_SUBLINK)
astate = initArrayResultAny(subplan->firstColType,
CurrentMemoryContext, true);
/*
* Must switch to per-query memory context.
*/
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
/*
* Set Params of this plan from parent plan correlation values. (Any
* calculation we have to do is done in the parent econtext, since the
* Param values don't need to have per-query lifetime.) Currently, we
* expect only MULTIEXPR_SUBLINK plans to have any correlation values.
*/
Assert(subplan->parParam == NIL || subLinkType == MULTIEXPR_SUBLINK);
Assert(list_length(subplan->parParam) == list_length(node->args));
forboth(l, subplan->parParam, pvar, node->args)
{
int paramid = lfirst_int(l);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->value = ExecEvalExprSwitchContext((ExprState *) lfirst(pvar),
econtext,
&(prm->isnull));
planstate->chgParam = bms_add_member(planstate->chgParam, paramid);
}
/*
* Setup the tuplestore writer for functionscan initplan
*
* Note that the file of tuplestore should not be deleted when
* closing file. This is due to the tuplestore reader is outside
* initplan, and reader will delete the file when it finished.
*/
if (subLinkType == INITPLAN_FUNC_SUBLINK && node->ts_state == NULL)
{
char rwfile_prefix[100];
function_scan_create_bufname_prefix(rwfile_prefix, sizeof(rwfile_prefix), subplan->plan_id);
node->ts_state = tuplestore_begin_heap(true, /* randomAccess */
false, /* interXact */
PlanStateOperatorMemKB((PlanState *)(node->planstate)));
tuplestore_make_shared(node->ts_state,
get_shareinput_fileset(),
rwfile_prefix);
}
/*
* Run the plan. (If it needs to be rescanned, the first ExecProcNode
* call will take care of that.)
*/
for (slot = ExecProcNode(planstate);
!TupIsNull(slot);
slot = ExecProcNode(planstate))
{
TupleDesc tdesc = slot->tts_tupleDescriptor;
int i = 1;
if (subLinkType == INITPLAN_FUNC_SUBLINK)
{
tuplestore_puttupleslot(node->ts_state, slot);
found = true;
continue;
}
if (subLinkType == EXISTS_SUBLINK || subLinkType == NOT_EXISTS_SUBLINK)
{
/* There can be only one setParam... */
int paramid = linitial_int(subplan->setParam);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->execPlan = NULL;
if (subLinkType == NOT_EXISTS_SUBLINK)
prm->value = BoolGetDatum(false);
else
prm->value = BoolGetDatum(true);
prm->isnull = false;
found = true;
break;
}
if (subLinkType == ARRAY_SUBLINK)
{
Datum dvalue;
bool disnull;
found = true;
/* stash away current value */
Assert(subplan->firstColType == TupleDescAttr(tdesc, 0)->atttypid);
dvalue = slot_getattr(slot, 1, &disnull);
astate = accumArrayResultAny(astate, dvalue, disnull,
subplan->firstColType, oldcontext);
/* keep scanning subplan to collect all values */
continue;
}
if (found &&
(subLinkType == EXPR_SUBLINK ||
subLinkType == MULTIEXPR_SUBLINK ||
subLinkType == ROWCOMPARE_SUBLINK))
ereport(ERROR,
(errcode(ERRCODE_CARDINALITY_VIOLATION),
errmsg("more than one row returned by a subquery used as an expression")));
found = true;
/*
* We need to copy the subplan's tuple into our own context, in case
* any of the params are pass-by-ref type --- the pointers stored in
* the param structs will point at this copied tuple! node->curTuple
* keeps track of the copied tuple for eventual freeing.
*/
if (node->curTuple)
heap_freetuple(node->curTuple);
node->curTuple = ExecCopySlotHeapTuple(slot);
/*
* Now set all the setParam params from the columns of the tuple
*/
foreach(l, subplan->setParam)
{
int paramid = lfirst_int(l);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->execPlan = NULL;
prm->value = heap_getattr(node->curTuple, i, tdesc,
&(prm->isnull));
i++;
}
}
/*
* Flush the tuplestore writer
*
*/
if (subLinkType == INITPLAN_FUNC_SUBLINK && node->ts_state)
{
tuplestore_freeze(node->ts_state);
}
if (!found)
{
if (subLinkType == EXISTS_SUBLINK || subLinkType == NOT_EXISTS_SUBLINK)
{
/* There can be only one setParam... */
int paramid = linitial_int(subplan->setParam);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->execPlan = NULL;
if (subLinkType == NOT_EXISTS_SUBLINK)
prm->value = BoolGetDatum(true);
else
prm->value = BoolGetDatum(false);
prm->isnull = false;
}
else
{
foreach(l, subplan->setParam)
{
int paramid = lfirst_int(l);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
prm->execPlan = NULL;
prm->value = (Datum) 0;
prm->isnull = true;
}
}
}
else if (subLinkType == ARRAY_SUBLINK)
{
/* There can be only one setParam... */
int paramid = linitial_int(subplan->setParam);
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
/*
* We build the result array in query context so it won't disappear;
* to avoid leaking memory across repeated calls, we have to remember
* the latest value, much as for curTuple above.
*/
if (node->curArray != PointerGetDatum(NULL))
pfree(DatumGetPointer(node->curArray));
node->curArray = makeArrayResultAny(astate,
econtext->ecxt_per_query_memory,
true);
prm->execPlan = NULL;
prm->value = node->curArray;
prm->isnull = false;
}
/* Clean up the interconnect. */
if (queryDesc && queryDesc->estate && queryDesc->estate->es_interconnect_is_setup)
{
TeardownInterconnect(queryDesc->estate->interconnect_context, false); /* following success on QD */
queryDesc->estate->interconnect_context = NULL;
queryDesc->estate->es_interconnect_is_setup = false;
}
/*
* If we dispatched to QEs, wait for completion.
*/
if (shouldDispatch &&
queryDesc && queryDesc->estate &&
queryDesc->estate->dispatcherState &&
queryDesc->estate->dispatcherState->primaryResults)
{
ErrorData *qeError = NULL;
CdbDispatchResults *pr = NULL;
CdbDispatcherState *ds = queryDesc->estate->dispatcherState;
int primaryWriterSliceIndex = PrimaryWriterSliceIndex(queryDesc->estate);
cdbdisp_checkDispatchResult(ds, DISPATCH_WAIT_NONE);
pr = cdbdisp_getDispatchResults(ds, &qeError);
if (qeError)
{
queryDesc->estate->dispatcherState = NULL;
FlushErrorState();
ReThrowError(qeError);
}
/* collect pgstat from QEs for current transaction level */
pgstat_combine_from_qe(pr, primaryWriterSliceIndex);
/* If EXPLAIN ANALYZE, collect execution stats from qExecs. */
if (planstate->instrument && planstate->instrument->need_cdb)
{
/* Jam stats into subplan's Instrumentation nodes. */
explainRecvStats = true;
cdbexplain_recvExecStats(planstate, ds->primaryResults,
LocallyExecutingSliceIndex(queryDesc->estate),
econtext->ecxt_estate->showstatctx);
}
/* Main plan use same estate, must reset dispatcherState */
queryDesc->estate->dispatcherState = NULL;
cdbdisp_destroyDispatcherState(ds);
}
}
PG_CATCH();
{
/* Restore memory high-water mark for root slice of main query. */
MemoryContextSetPeakSpace(planstate->state->es_query_cxt, savepeakspace);
if (oldcontext)
MemoryContextSwitchTo(oldcontext);
/* restore scan direction */
estate->es_direction = dir;
/*
* Clean up the interconnect.
* CDB TODO: Is this needed following failure on QD?
*/
if (queryDesc && queryDesc->estate && queryDesc->estate->es_interconnect_is_setup)
{
TeardownInterconnect(queryDesc->estate->interconnect_context, true);
queryDesc->estate->interconnect_context = NULL;
queryDesc->estate->es_interconnect_is_setup = false;
}
/*
* Request any commands still executing on qExecs to stop.
* Wait for them to finish and clean up the dispatching structures.
* Replace current error info with QE error info if more interesting.
*/
if (shouldDispatch && queryDesc && queryDesc->estate &&
queryDesc->estate->dispatcherState)
{
CdbDispatcherState *ds = queryDesc->estate->dispatcherState;
queryDesc->estate->dispatcherState = NULL;
CdbDispatchHandleError(ds);
}
PG_RE_THROW();
}
PG_END_TRY();
/* If EXPLAIN ANALYZE, collect local execution stats. */
if (Gp_role == GP_ROLE_DISPATCH && planstate->instrument && planstate->instrument->need_cdb)
cdbexplain_localExecStats(planstate, econtext->ecxt_estate->showstatctx);
/* Restore memory high-water mark for root slice of main query. */
MemoryContextSetPeakSpace(planstate->state->es_query_cxt, savepeakspace);
MemoryContextSwitchTo(oldcontext);
/* restore scan direction */
estate->es_direction = dir;
}
/*
* ExecSetParamPlanMulti
*
* Apply ExecSetParamPlan to evaluate any not-yet-evaluated initplan output
* parameters whose ParamIDs are listed in "params". Any listed params that
* are not initplan outputs are ignored.
*
* As with ExecSetParamPlan, any ExprContext belonging to the current EState
* can be used, but in principle a shorter-lived ExprContext is better than a
* longer-lived one.
*/
void
ExecSetParamPlanMulti(const Bitmapset *params, ExprContext *econtext, QueryDesc *queryDesc)
{
int paramid;
paramid = -1;
while ((paramid = bms_next_member(params, paramid)) >= 0)
{
ParamExecData *prm = &(econtext->ecxt_param_exec_vals[paramid]);
if (prm->execPlan != NULL)
{
/* Parameter not evaluated yet, so go do it */
ExecSetParamPlan(prm->execPlan, econtext, queryDesc);
/* ExecSetParamPlan should have processed this param... */
Assert(prm->execPlan == NULL);
}
}
}
/*
* Mark an initplan as needing recalculation
*/
void
ExecReScanSetParamPlan(SubPlanState *node, PlanState *parent)
{
PlanState *planstate = node->planstate;
SubPlan *subplan = node->subplan;
EState *estate = parent->state;
ListCell *l;
/* sanity checks */
if (subplan->parParam != NIL)
elog(ERROR, "direct correlated subquery unsupported as initplan");
if (subplan->setParam == NIL)
elog(ERROR, "setParam list of initplan is empty");
if (bms_is_empty(planstate->plan->extParam))
elog(ERROR, "extParam set of initplan is empty");
/*
* Don't actually re-scan: it'll happen inside ExecSetParamPlan if needed.
*/
/*
* Mark this subplan's output parameters as needing recalculation.
*
* CTE subplans are never executed via parameter recalculation; instead
* they get run when called by nodeCtescan.c. So don't mark the output
* parameter of a CTE subplan as dirty, but do set the chgParam bit for it
* so that dependent plan nodes will get told to rescan.
*/
foreach(l, subplan->setParam)
{
int paramid = lfirst_int(l);
ParamExecData *prm = &(estate->es_param_exec_vals[paramid]);
if (subplan->subLinkType != CTE_SUBLINK)
prm->execPlan = node;
parent->chgParam = bms_add_member(parent->chgParam, paramid);
}
}
/*
* ExecInitAlternativeSubPlan
*
* Initialize for execution of one of a set of alternative subplans.
*/
AlternativeSubPlanState *
ExecInitAlternativeSubPlan(AlternativeSubPlan *asplan, PlanState *parent)
{
AlternativeSubPlanState *asstate = makeNode(AlternativeSubPlanState);
double num_calls;
SubPlan *subplan1;
SubPlan *subplan2;
Cost cost1;
Cost cost2;
ListCell *lc;
asstate->subplan = asplan;
/*
* Initialize subplans. (Can we get away with only initializing the one
* we're going to use?)
*/
foreach(lc, asplan->subplans)
{
SubPlan *sp = lfirst_node(SubPlan, lc);
SubPlanState *sps = ExecInitSubPlan(sp, parent);
asstate->subplans = lappend(asstate->subplans, sps);
parent->subPlan = lappend(parent->subPlan, sps);
}
/*
* Select the one to be used. For this, we need an estimate of the number
* of executions of the subplan. We use the number of output rows
* expected from the parent plan node. This is a good estimate if we are
* in the parent's targetlist, and an underestimate (but probably not by
* more than a factor of 2) if we are in the qual.
*/
num_calls = parent->plan->plan_rows;
/*
* The planner saved enough info so that we don't have to work very hard
* to estimate the total cost, given the number-of-calls estimate.
*/
Assert(list_length(asplan->subplans) == 2);
subplan1 = (SubPlan *) linitial(asplan->subplans);
subplan2 = (SubPlan *) lsecond(asplan->subplans);
cost1 = subplan1->startup_cost + num_calls * subplan1->per_call_cost;
cost2 = subplan2->startup_cost + num_calls * subplan2->per_call_cost;
if (cost1 < cost2)
asstate->active = 0;
else
asstate->active = 1;
return asstate;
}
/*
* ExecAlternativeSubPlan
*
* Execute one of a set of alternative subplans.
*
* Note: in future we might consider changing to different subplans on the
* fly, in case the original rowcount estimate turns out to be way off.
*/
Datum
ExecAlternativeSubPlan(AlternativeSubPlanState *node,
ExprContext *econtext,
bool *isNull)
{
/* Just pass control to the active subplan */
SubPlanState *activesp = list_nth_node(SubPlanState,
node->subplans, node->active);
return ExecSubPlan(activesp, econtext, isNull);
}
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