PostgreSQL/src/backend/executor/nodeBitmapIndexscan.c
Tom Lane a98871b7ac Tweak indexscan machinery to avoid taking an AccessShareLock on an index
if we already have a stronger lock due to the index's table being the
update target table of the query.  Same optimization I applied earlier
at the table level.  There doesn't seem to be much interest in the more
radical idea of not locking indexes at all, so do what we can ...
2005-12-03 05:51:03 +00:00

327 lines
9.2 KiB
C

/*-------------------------------------------------------------------------
*
* nodeBitmapIndexscan.c
* Routines to support bitmapped index scans of relations
*
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/nodeBitmapIndexscan.c,v 1.14 2005/12/03 05:51:01 tgl Exp $
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* MultiExecBitmapIndexScan scans a relation using index.
* ExecInitBitmapIndexScan creates and initializes state info.
* ExecBitmapIndexReScan prepares to rescan the plan.
* ExecEndBitmapIndexScan releases all storage.
*/
#include "postgres.h"
#include "access/genam.h"
#include "executor/execdebug.h"
#include "executor/instrument.h"
#include "executor/nodeBitmapIndexscan.h"
#include "executor/nodeIndexscan.h"
#include "miscadmin.h"
#include "utils/memutils.h"
/* ----------------------------------------------------------------
* MultiExecBitmapIndexScan(node)
* ----------------------------------------------------------------
*/
Node *
MultiExecBitmapIndexScan(BitmapIndexScanState *node)
{
#define MAX_TIDS 1024
TIDBitmap *tbm;
IndexScanDesc scandesc;
ItemPointerData tids[MAX_TIDS];
int32 ntids;
double nTuples = 0;
bool doscan;
/* must provide our own instrumentation support */
if (node->ss.ps.instrument)
InstrStartNode(node->ss.ps.instrument);
/*
* extract necessary information from index scan node
*/
scandesc = node->biss_ScanDesc;
/*
* If we have runtime keys and they've not already been set up, do it now.
* Array keys are also treated as runtime keys; note that if ExecReScan
* returns with biss_RuntimeKeysReady still false, then there is an
* empty array key so we should do nothing.
*/
if (!node->biss_RuntimeKeysReady &&
(node->biss_NumRuntimeKeys != 0 || node->biss_NumArrayKeys != 0))
{
ExecReScan((PlanState *) node, NULL);
doscan = node->biss_RuntimeKeysReady;
}
else
doscan = true;
/*
* Prepare the result bitmap. Normally we just create a new one to pass
* back; however, our parent node is allowed to store a pre-made one into
* node->biss_result, in which case we just OR our tuple IDs into the
* existing bitmap. (This saves needing explicit UNION steps.)
*/
if (node->biss_result)
{
tbm = node->biss_result;
node->biss_result = NULL; /* reset for next time */
}
else
{
/* XXX should we use less than work_mem for this? */
tbm = tbm_create(work_mem * 1024L);
}
/*
* Get TIDs from index and insert into bitmap
*/
while (doscan)
{
bool more = index_getmulti(scandesc, tids, MAX_TIDS, &ntids);
if (ntids > 0)
{
tbm_add_tuples(tbm, tids, ntids);
nTuples += ntids;
}
CHECK_FOR_INTERRUPTS();
if (!more)
{
doscan = ExecIndexAdvanceArrayKeys(node->biss_ArrayKeys,
node->biss_NumArrayKeys);
if (doscan) /* reset index scan */
index_rescan(node->biss_ScanDesc, node->biss_ScanKeys);
}
}
/* must provide our own instrumentation support */
if (node->ss.ps.instrument)
InstrStopNodeMulti(node->ss.ps.instrument, nTuples);
return (Node *) tbm;
}
/* ----------------------------------------------------------------
* ExecBitmapIndexReScan(node)
*
* Recalculates the value of the scan keys whose value depends on
* information known at runtime and rescans the indexed relation.
* ----------------------------------------------------------------
*/
void
ExecBitmapIndexReScan(BitmapIndexScanState *node, ExprContext *exprCtxt)
{
ExprContext *econtext;
econtext = node->biss_RuntimeContext; /* context for runtime keys */
if (econtext)
{
/*
* If we are being passed an outer tuple, save it for runtime key
* calc.
*/
if (exprCtxt != NULL)
econtext->ecxt_outertuple = exprCtxt->ecxt_outertuple;
/*
* Reset the runtime-key context so we don't leak memory as each outer
* tuple is scanned. Note this assumes that we will recalculate *all*
* runtime keys on each call.
*/
ResetExprContext(econtext);
}
/*
* If we are doing runtime key calculations (ie, the index keys depend on
* data from an outer scan), compute the new key values.
*
* Array keys are also treated as runtime keys; note that if we
* return with biss_RuntimeKeysReady still false, then there is an
* empty array key so no index scan is needed.
*/
if (node->biss_NumRuntimeKeys != 0)
ExecIndexEvalRuntimeKeys(econtext,
node->biss_RuntimeKeys,
node->biss_NumRuntimeKeys);
if (node->biss_NumArrayKeys != 0)
node->biss_RuntimeKeysReady =
ExecIndexEvalArrayKeys(econtext,
node->biss_ArrayKeys,
node->biss_NumArrayKeys);
else
node->biss_RuntimeKeysReady = true;
/* reset index scan */
if (node->biss_RuntimeKeysReady)
index_rescan(node->biss_ScanDesc, node->biss_ScanKeys);
}
/* ----------------------------------------------------------------
* ExecEndBitmapIndexScan
* ----------------------------------------------------------------
*/
void
ExecEndBitmapIndexScan(BitmapIndexScanState *node)
{
Relation indexRelationDesc;
IndexScanDesc indexScanDesc;
/*
* extract information from the node
*/
indexRelationDesc = node->biss_RelationDesc;
indexScanDesc = node->biss_ScanDesc;
/*
* Free the exprcontext ... now dead code, see ExecFreeExprContext
*/
#ifdef NOT_USED
if (node->biss_RuntimeContext)
FreeExprContext(node->biss_RuntimeContext);
#endif
/*
* close the index relation
*/
index_endscan(indexScanDesc);
index_close(indexRelationDesc);
}
/* ----------------------------------------------------------------
* ExecInitBitmapIndexScan
*
* Initializes the index scan's state information.
* ----------------------------------------------------------------
*/
BitmapIndexScanState *
ExecInitBitmapIndexScan(BitmapIndexScan *node, EState *estate)
{
BitmapIndexScanState *indexstate;
bool relistarget;
/*
* create state structure
*/
indexstate = makeNode(BitmapIndexScanState);
indexstate->ss.ps.plan = (Plan *) node;
indexstate->ss.ps.state = estate;
/* normally we don't make the result bitmap till runtime */
indexstate->biss_result = NULL;
/*
* Miscellaneous initialization
*
* We do not need a standard exprcontext for this node, though we may
* decide below to create a runtime-key exprcontext
*/
/*
* initialize child expressions
*
* We don't need to initialize targetlist or qual since neither are used.
*
* Note: we don't initialize all of the indexqual expression, only the
* sub-parts corresponding to runtime keys (see below).
*/
#define BITMAPINDEXSCAN_NSLOTS 0
/*
* Initialize index-specific scan state
*/
indexstate->biss_RuntimeKeysReady = false;
CXT1_printf("ExecInitBitmapIndexScan: context is %d\n", CurrentMemoryContext);
/*
* build the index scan keys from the index qualification
*/
ExecIndexBuildScanKeys((PlanState *) indexstate,
node->indexqual,
node->indexstrategy,
node->indexsubtype,
&indexstate->biss_ScanKeys,
&indexstate->biss_NumScanKeys,
&indexstate->biss_RuntimeKeys,
&indexstate->biss_NumRuntimeKeys,
&indexstate->biss_ArrayKeys,
&indexstate->biss_NumArrayKeys);
/*
* If we have runtime keys or array keys, we need an ExprContext to
* evaluate them. We could just create a "standard" plan node exprcontext,
* but to keep the code looking similar to nodeIndexscan.c, it seems
* better to stick with the approach of using a separate ExprContext.
*/
if (indexstate->biss_NumRuntimeKeys != 0 ||
indexstate->biss_NumArrayKeys != 0)
{
ExprContext *stdecontext = indexstate->ss.ps.ps_ExprContext;
ExecAssignExprContext(estate, &indexstate->ss.ps);
indexstate->biss_RuntimeContext = indexstate->ss.ps.ps_ExprContext;
indexstate->ss.ps.ps_ExprContext = stdecontext;
}
else
{
indexstate->biss_RuntimeContext = NULL;
}
/*
* We do not open or lock the base relation here. We assume that an
* ancestor BitmapHeapScan node is holding AccessShareLock (or better)
* on the heap relation throughout the execution of the plan tree.
*/
indexstate->ss.ss_currentRelation = NULL;
indexstate->ss.ss_currentScanDesc = NULL;
/*
* Open the index relation and initialize relation and scan descriptors.
* Note we acquire no locks here; the index machinery does its own locks
* and unlocks. (We rely on having a lock on the parent table to
* ensure the index won't go away!) Furthermore, if the parent table
* is one of the target relations of the query, then InitPlan already
* opened and write-locked the index, so we can tell the index machinery
* not to bother getting an extra lock.
*/
indexstate->biss_RelationDesc = index_open(node->indexid);
relistarget = ExecRelationIsTargetRelation(estate, node->scan.scanrelid);
indexstate->biss_ScanDesc =
index_beginscan_multi(indexstate->biss_RelationDesc,
!relistarget,
estate->es_snapshot,
indexstate->biss_NumScanKeys,
indexstate->biss_ScanKeys);
/*
* all done.
*/
return indexstate;
}
int
ExecCountSlotsBitmapIndexScan(BitmapIndexScan *node)
{
return ExecCountSlotsNode(outerPlan((Plan *) node)) +
ExecCountSlotsNode(innerPlan((Plan *) node)) + BITMAPINDEXSCAN_NSLOTS;
}