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First cut at implementing IN (and NOT IN) via hashtables. There is

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more to be done yet, but this is a good start.
This commit is contained in:
Tom Lane
2003-01-12 04:03:34 +00:00
parent 3e54e26bcf
commit 19b886332a
7 changed files with 712 additions and 132 deletions
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508
src/backend/executor/nodeSubplan.c
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/executor/nodeSubplan.c,v 1.42 2003/01/10 21:08:08 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/executor/nodeSubplan.c,v 1.43 2003/01/12 04:03:34 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -22,11 +22,24 @@
#include "access/heapam.h"
#include "executor/executor.h"
#include "executor/nodeSubplan.h"
#include "nodes/makefuncs.h"
#include "parser/parse_expr.h"
#include "tcop/pquery.h"
static Datum ExecHashSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull);
static Datum ExecScanSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull);
static void buildSubPlanHash(SubPlanState *node);
static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot);
static bool tupleAllNulls(HeapTuple tuple);
/* ----------------------------------------------------------------
* ExecSubPlan(node)
* ExecSubPlan
* ----------------------------------------------------------------
*/
Datum
@ -35,6 +48,155 @@ ExecSubPlan(SubPlanState *node,
bool *isNull)
{
SubPlan *subplan = (SubPlan *) node->xprstate.expr;
if (subplan->setParam != NIL)
elog(ERROR, "ExecSubPlan: can't set parent params from subquery");
if (subplan->useHashTable)
return ExecHashSubPlan(node, econtext, isNull);
else
return ExecScanSubPlan(node, econtext, isNull);
}
/*
* ExecHashSubPlan: store subselect result in an in-memory hash table
*/
static Datum
ExecHashSubPlan(SubPlanState *node,
ExprContext *econtext,
bool *isNull)
{
SubPlan *subplan = (SubPlan *) node->xprstate.expr;
PlanState *planstate = node->planstate;
ExprContext *innerecontext = node->innerecontext;
TupleTableSlot *slot;
HeapTuple tup;
/* Shouldn't have any direct correlation Vars */
if (subplan->parParam != NIL || node->args != NIL)
elog(ERROR, "ExecHashSubPlan: 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 != NIL)
buildSubPlanHash(node);
/*
* 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, NULL);
tup = slot->val;
/*
* 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.
*/
/*
* Since the hashtable routines will use innerecontext's per-tuple
* memory as working memory, be sure to reset it for each tuple.
*/
ResetExprContext(innerecontext);
/*
* 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 (HeapTupleNoNulls(tup))
{
if (node->havehashrows &&
LookupTupleHashEntry(node->hashtable, slot, NULL) != NULL)
{
ExecClearTuple(slot);
return BoolGetDatum(true);
}
if (node->havenullrows &&
findPartialMatch(node->hashnulls, slot))
{
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 (tupleAllNulls(tup))
{
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))
{
ExecClearTuple(slot);
*isNull = true;
return BoolGetDatum(false);
}
if (node->havehashrows &&
findPartialMatch(node->hashtable, slot))
{
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 = (SubPlan *) node->xprstate.expr;
PlanState *planstate = node->planstate;
SubLinkType subLinkType = subplan->subLinkType;
bool useOr = subplan->useOr;
@ -52,9 +214,6 @@ ExecSubPlan(SubPlanState *node,
*/
oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
if (subplan->setParam != NIL)
elog(ERROR, "ExecSubPlan: can't set parent params from subquery");
/*
* Set Params of this plan from parent plan correlation Vars
*/
@ -267,6 +426,203 @@ ExecSubPlan(SubPlanState *node,
return result;
}
/*
* buildSubPlanHash: load hash table by scanning subplan output.
*/
static void
buildSubPlanHash(SubPlanState *node)
{
SubPlan *subplan = (SubPlan *) node->xprstate.expr;
PlanState *planstate = node->planstate;
int ncols = length(node->exprs);
ExprContext *innerecontext = node->innerecontext;
MemoryContext tempcxt = innerecontext->ecxt_per_tuple_memory;
MemoryContext oldcontext;
int nbuckets;
TupleTableSlot *slot;
Assert(subplan->subLinkType == ANY_SUBLINK);
Assert(!subplan->useOr);
/*
* If we already had any hash tables, destroy 'em; then 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->tablecxt);
node->hashtable = NULL;
node->hashnulls = NULL;
node->havehashrows = false;
node->havenullrows = false;
nbuckets = (int) ceil(planstate->plan->plan_rows);
if (nbuckets < 1)
nbuckets = 1;
node->hashtable = BuildTupleHashTable(ncols,
node->keyColIdx,
node->eqfunctions,
nbuckets,
sizeof(TupleHashEntryData),
node->tablecxt,
tempcxt);
if (!subplan->unknownEqFalse)
{
if (ncols == 1)
nbuckets = 1; /* there can only be one entry */
else
{
nbuckets /= 16;
if (nbuckets < 1)
nbuckets = 1;
}
node->hashnulls = BuildTupleHashTable(ncols,
node->keyColIdx,
node->eqfunctions,
nbuckets,
sizeof(TupleHashEntryData),
node->tablecxt,
tempcxt);
}
/*
* We are probably in a short-lived expression-evaluation context.
* Switch to the child plan's per-query context for calling ExecProcNode.
*/
oldcontext = MemoryContextSwitchTo(node->sub_estate->es_query_cxt);
/*
* Reset subplan to start.
*/
ExecReScan(planstate, NULL);
/*
* 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))
{
HeapTuple tup = slot->val;
TupleDesc tdesc = slot->ttc_tupleDescriptor;
int col = 1;
List *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 = lfirsti(plst);
ParamExecData *prmdata;
prmdata = &(innerecontext->ecxt_param_exec_vals[paramid]);
Assert(prmdata->execPlan == NULL);
prmdata->value = heap_getattr(tup, col, tdesc,
&(prmdata->isnull));
col++;
}
slot = ExecProject(node->projRight, NULL);
tup = slot->val;
/*
* If result contains any nulls, store separately or not at all.
* (Since we know the projection tuple has no junk columns, we
* can just look at the overall hasnull info bit, instead of
* groveling through the columns.)
*/
if (HeapTupleNoNulls(tup))
{
(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 in hash computation or comparison routines.
*/
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.
*/
ExecClearTuple(node->projRight->pi_slot);
MemoryContextSwitchTo(oldcontext);
}
/*
* 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.
*/
static bool
findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
{
int numCols = hashtable->numCols;
AttrNumber *keyColIdx = hashtable->keyColIdx;
HeapTuple tuple = slot->val;
TupleDesc tupdesc = slot->ttc_tupleDescriptor;
TupleHashIterator hashiter;
TupleHashEntry entry;
ResetTupleHashIterator(&hashiter);
while ((entry = ScanTupleHashTable(hashtable, &hashiter)) != NULL)
{
if (!execTuplesUnequal(entry->firstTuple,
tuple,
tupdesc,
numCols, keyColIdx,
hashtable->eqfunctions,
hashtable->tempcxt))
return true;
}
return false;
}
/*
* tupleAllNulls: is the tuple completely NULL?
*/
static bool
tupleAllNulls(HeapTuple tuple)
{
int ncols = tuple->t_data->t_natts;
int i;
for (i = 1; i <= ncols; i++)
{
if (!heap_attisnull(tuple, i))
return false;
}
return true;
}
/* ----------------------------------------------------------------
* ExecInitSubPlan
* ----------------------------------------------------------------
@ -289,8 +645,14 @@ ExecInitSubPlan(SubPlanState *node, EState *estate)
*/
node->needShutdown = false;
node->curTuple = NULL;
node->projLeft = NULL;
node->projRight = NULL;
node->hashtable = NULL;
node->hashnulls = NULL;
node->tablecxt = NULL;
node->innerecontext = NULL;
node->keyColIdx = NULL;
node->eqfunctions = NULL;
/*
* create an EState for the subplan
@ -343,6 +705,137 @@ ExecInitSubPlan(SubPlanState *node, EState *estate)
* it, for others - it doesn't matter...
*/
}
/*
* 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 tupDesc;
TupleTable tupTable;
TupleTableSlot *slot;
List *lefttlist,
*righttlist,
*leftptlist,
*rightptlist,
*lexpr;
/* We need a memory context to hold the hash table(s) */
node->tablecxt =
AllocSetContextCreate(CurrentMemoryContext,
"Subplan HashTable Context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
/* and a short-lived exprcontext for function evaluation */
node->innerecontext = CreateExprContext(estate);
/* Silly little array of column numbers 1..n */
ncols = length(node->exprs);
node->keyColIdx = (AttrNumber *) palloc(ncols * sizeof(AttrNumber));
for (i = 0; i < ncols; i++)
node->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 need both the ExprState list
* (for ExecProject) and the underlying parse Exprs (for
* ExecTypeFromTL).
*
* We also extract the combining operators themselves to initialize
* the equality functions for the hash tables.
*/
lefttlist = righttlist = NIL;
leftptlist = rightptlist = NIL;
node->eqfunctions = (FmgrInfo *) palloc(ncols * sizeof(FmgrInfo));
i = 1;
foreach(lexpr, node->exprs)
{
FuncExprState *fstate = (FuncExprState *) lfirst(lexpr);
OpExpr *opexpr = (OpExpr *) fstate->xprstate.expr;
ExprState *exstate;
Expr *expr;
TargetEntry *tle;
GenericExprState *tlestate;
Assert(IsA(fstate, FuncExprState));
Assert(IsA(opexpr, OpExpr));
Assert(length(fstate->args) == 2);
/* Process lefthand argument */
exstate = (ExprState *) lfirst(fstate->args);
expr = exstate->expr;
tle = makeTargetEntry(makeResdom(i,
exprType((Node *) expr),
exprTypmod((Node *) expr),
NULL,
false),
expr);
tlestate = makeNode(GenericExprState);
tlestate->xprstate.expr = (Expr *) tle;
tlestate->arg = exstate;
lefttlist = lappend(lefttlist, tlestate);
leftptlist = lappend(leftptlist, tle);
/* Process righthand argument */
exstate = (ExprState *) lsecond(fstate->args);
expr = exstate->expr;
tle = makeTargetEntry(makeResdom(i,
exprType((Node *) expr),
exprTypmod((Node *) expr),
NULL,
false),
expr);
tlestate = makeNode(GenericExprState);
tlestate->xprstate.expr = (Expr *) tle;
tlestate->arg = exstate;
righttlist = lappend(righttlist, tlestate);
rightptlist = lappend(rightptlist, tle);
/* Lookup the combining function */
fmgr_info(opexpr->opfuncid, &node->eqfunctions[i-1]);
i++;
}
/*
* Create a tupletable to hold these tuples. (Note: we never bother
* to free the tupletable explicitly; that's okay because it will
* never store raw disk tuples that might have associated buffer
* pins. The only resource involved is memory, which will be
* cleaned up by freeing the query context.)
*/
tupTable = ExecCreateTupleTable(2);
/*
* 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.
*/
tupDesc = ExecTypeFromTL(leftptlist, false);
slot = ExecAllocTableSlot(tupTable);
ExecSetSlotDescriptor(slot, tupDesc, true);
node->projLeft = ExecBuildProjectionInfo(lefttlist,
NULL,
slot);
tupDesc = ExecTypeFromTL(rightptlist, false);
slot = ExecAllocTableSlot(tupTable);
ExecSetSlotDescriptor(slot, tupDesc, true);
node->projRight = ExecBuildProjectionInfo(righttlist,
node->innerecontext,
slot);
}
}
/* ----------------------------------------------------------------
@ -476,11 +969,6 @@ ExecEndSubPlan(SubPlanState *node)
node->planstate = NULL;
node->needShutdown = false;
}
if (node->curTuple)
{
heap_freetuple(node->curTuple);
node->curTuple = NULL;
}
}
void