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postgresql/src/backend/executor/nodeBitmapHeapscan.c

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/*-------------------------------------------------------------------------
*
* nodeBitmapHeapscan.c
* Routines to support bitmapped scans of relations
*
* NOTE: it is critical that this plan type only be used with MVCC-compliant
* snapshots (ie, regular snapshots, not SnapshotAny or one of the other
* special snapshots). The reason is that since index and heap scans are
* decoupled, there can be no assurance that the index tuple prompting a
* visit to a particular heap TID still exists when the visit is made.
* Therefore the tuple might not exist anymore either (which is OK because
* heap_fetch will cope) --- but worse, the tuple slot could have been
* re-used for a newer tuple. With an MVCC snapshot the newer tuple is
* certain to fail the time qual and so it will not be mistakenly returned,
* but with anything else we might return a tuple that doesn't meet the
* required index qual conditions.
*
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/executor/nodeBitmapHeapscan.c
*
*-------------------------------------------------------------------------
*/
/*
* INTERFACE ROUTINES
* ExecBitmapHeapScan scans a relation using bitmap info
* ExecBitmapHeapNext workhorse for above
* ExecInitBitmapHeapScan creates and initializes state info.
* ExecReScanBitmapHeapScan prepares to rescan the plan.
* ExecEndBitmapHeapScan releases all storage.
*/
#include "postgres.h"
#include <math.h>
#include "access/relscan.h"
#include "access/tableam.h"
#include "access/transam.h"
#include "access/visibilitymap.h"
#include "executor/execdebug.h"
#include "executor/nodeBitmapHeapscan.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/predicate.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/spccache.h"
static TupleTableSlot *BitmapHeapNext(BitmapHeapScanState *node);
static inline void BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate);
static inline void BitmapAdjustPrefetchIterator(BitmapHeapScanState *node,
TBMIterateResult *tbmres);
static inline void BitmapAdjustPrefetchTarget(BitmapHeapScanState *node);
static inline void BitmapPrefetch(BitmapHeapScanState *node,
TableScanDesc scan);
static bool BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate);
/* ----------------------------------------------------------------
* BitmapHeapNext
*
* Retrieve next tuple from the BitmapHeapScan node's currentRelation
* ----------------------------------------------------------------
*/
static TupleTableSlot *
BitmapHeapNext(BitmapHeapScanState *node)
{
ExprContext *econtext;
TableScanDesc scan;
TIDBitmap *tbm;
TBMIterator *tbmiterator = NULL;
TBMSharedIterator *shared_tbmiterator = NULL;
TBMIterateResult *tbmres;
TupleTableSlot *slot;
ParallelBitmapHeapState *pstate = node->pstate;
dsa_area *dsa = node->ss.ps.state->es_query_dsa;
/*
* extract necessary information from index scan node
*/
econtext = node->ss.ps.ps_ExprContext;
slot = node->ss.ss_ScanTupleSlot;
scan = node->ss.ss_currentScanDesc;
tbm = node->tbm;
if (pstate == NULL)
tbmiterator = node->tbmiterator;
else
shared_tbmiterator = node->shared_tbmiterator;
tbmres = node->tbmres;
/*
* If we haven't yet performed the underlying index scan, do it, and begin
* the iteration over the bitmap.
*
* For prefetching, we use *two* iterators, one for the pages we are
* actually scanning and another that runs ahead of the first for
* prefetching. node->prefetch_pages tracks exactly how many pages ahead
* the prefetch iterator is. Also, node->prefetch_target tracks the
* desired prefetch distance, which starts small and increases up to the
* node->prefetch_maximum. This is to avoid doing a lot of prefetching in
* a scan that stops after a few tuples because of a LIMIT.
*/
if (!node->initialized)
{
if (!pstate)
{
tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node));
if (!tbm || !IsA(tbm, TIDBitmap))
elog(ERROR, "unrecognized result from subplan");
node->tbm = tbm;
node->tbmiterator = tbmiterator = tbm_begin_iterate(tbm);
node->tbmres = tbmres = NULL;
#ifdef USE_PREFETCH
if (node->prefetch_maximum > 0)
{
node->prefetch_iterator = tbm_begin_iterate(tbm);
node->prefetch_pages = 0;
node->prefetch_target = -1;
}
#endif /* USE_PREFETCH */
}
else
{
/*
* The leader will immediately come out of the function, but
* others will be blocked until leader populates the TBM and wakes
* them up.
*/
if (BitmapShouldInitializeSharedState(pstate))
{
tbm = (TIDBitmap *) MultiExecProcNode(outerPlanState(node));
if (!tbm || !IsA(tbm, TIDBitmap))
elog(ERROR, "unrecognized result from subplan");
node->tbm = tbm;
/*
* Prepare to iterate over the TBM. This will return the
* dsa_pointer of the iterator state which will be used by
* multiple processes to iterate jointly.
*/
pstate->tbmiterator = tbm_prepare_shared_iterate(tbm);
#ifdef USE_PREFETCH
if (node->prefetch_maximum > 0)
{
pstate->prefetch_iterator =
tbm_prepare_shared_iterate(tbm);
/*
* We don't need the mutex here as we haven't yet woke up
* others.
*/
pstate->prefetch_pages = 0;
pstate->prefetch_target = -1;
}
#endif
/* We have initialized the shared state so wake up others. */
BitmapDoneInitializingSharedState(pstate);
}
/* Allocate a private iterator and attach the shared state to it */
node->shared_tbmiterator = shared_tbmiterator =
tbm_attach_shared_iterate(dsa, pstate->tbmiterator);
node->tbmres = tbmres = NULL;
#ifdef USE_PREFETCH
if (node->prefetch_maximum > 0)
{
node->shared_prefetch_iterator =
tbm_attach_shared_iterate(dsa, pstate->prefetch_iterator);
}
#endif /* USE_PREFETCH */
}
node->initialized = true;
}
for (;;)
{
bool skip_fetch;
CHECK_FOR_INTERRUPTS();
/*
* Get next page of results if needed
*/
if (tbmres == NULL)
{
if (!pstate)
node->tbmres = tbmres = tbm_iterate(tbmiterator);
else
node->tbmres = tbmres = tbm_shared_iterate(shared_tbmiterator);
if (tbmres == NULL)
{
/* no more entries in the bitmap */
break;
}
BitmapAdjustPrefetchIterator(node, tbmres);
/*
* We can skip fetching the heap page if we don't need any fields
* from the heap, and the bitmap entries don't need rechecking,
* and all tuples on the page are visible to our transaction.
*
* XXX: It's a layering violation that we do these checks above
* tableam, they should probably moved below it at some point.
*/
skip_fetch = (node->can_skip_fetch &&
!tbmres->recheck &&
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
tbmres->blockno,
&node->vmbuffer));
if (skip_fetch)
{
/* can't be lossy in the skip_fetch case */
Assert(tbmres->ntuples >= 0);
/*
* The number of tuples on this page is put into
* node->return_empty_tuples.
*/
node->return_empty_tuples = tbmres->ntuples;
}
else if (!table_scan_bitmap_next_block(scan, tbmres))
{
/* AM doesn't think this block is valid, skip */
continue;
}
if (tbmres->ntuples >= 0)
node->exact_pages++;
else
node->lossy_pages++;
/* Adjust the prefetch target */
BitmapAdjustPrefetchTarget(node);
}
else
{
/*
* Continuing in previously obtained page.
*/
#ifdef USE_PREFETCH
/*
* Try to prefetch at least a few pages even before we get to the
* second page if we don't stop reading after the first tuple.
*/
if (!pstate)
{
if (node->prefetch_target < node->prefetch_maximum)
node->prefetch_target++;
}
else if (pstate->prefetch_target < node->prefetch_maximum)
{
/* take spinlock while updating shared state */
SpinLockAcquire(&pstate->mutex);
if (pstate->prefetch_target < node->prefetch_maximum)
pstate->prefetch_target++;
SpinLockRelease(&pstate->mutex);
}
#endif /* USE_PREFETCH */
}
/*
* We issue prefetch requests *after* fetching the current page to try
* to avoid having prefetching interfere with the main I/O. Also, this
* should happen only when we have determined there is still something
* to do on the current page, else we may uselessly prefetch the same
* page we are just about to request for real.
*
* XXX: It's a layering violation that we do these checks above
* tableam, they should probably moved below it at some point.
*/
BitmapPrefetch(node, scan);
if (node->return_empty_tuples > 0)
{
/*
* If we don't have to fetch the tuple, just return nulls.
*/
ExecStoreAllNullTuple(slot);
if (--node->return_empty_tuples == 0)
{
/* no more tuples to return in the next round */
node->tbmres = tbmres = NULL;
}
}
else
{
/*
* Attempt to fetch tuple from AM.
*/
if (!table_scan_bitmap_next_tuple(scan, tbmres, slot))
{
/* nothing more to look at on this page */
node->tbmres = tbmres = NULL;
continue;
}
/*
* If we are using lossy info, we have to recheck the qual
* conditions at every tuple.
*/
if (tbmres->recheck)
{
econtext->ecxt_scantuple = slot;
if (!ExecQualAndReset(node->bitmapqualorig, econtext))
{
/* Fails recheck, so drop it and loop back for another */
InstrCountFiltered2(node, 1);
ExecClearTuple(slot);
continue;
}
}
}
/* OK to return this tuple */
return slot;
}
/*
* if we get here it means we are at the end of the scan..
*/
return ExecClearTuple(slot);
}
/*
* BitmapDoneInitializingSharedState - Shared state is initialized
*
* By this time the leader has already populated the TBM and initialized the
* shared state so wake up other processes.
*/
static inline void
BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate)
{
SpinLockAcquire(&pstate->mutex);
pstate->state = BM_FINISHED;
SpinLockRelease(&pstate->mutex);
ConditionVariableBroadcast(&pstate->cv);
}
/*
* BitmapAdjustPrefetchIterator - Adjust the prefetch iterator
*/
static inline void
BitmapAdjustPrefetchIterator(BitmapHeapScanState *node,
TBMIterateResult *tbmres)
{
#ifdef USE_PREFETCH
ParallelBitmapHeapState *pstate = node->pstate;
if (pstate == NULL)
{
TBMIterator *prefetch_iterator = node->prefetch_iterator;
if (node->prefetch_pages > 0)
{
/* The main iterator has closed the distance by one page */
node->prefetch_pages--;
}
else if (prefetch_iterator)
{
/* Do not let the prefetch iterator get behind the main one */
TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
if (tbmpre == NULL || tbmpre->blockno != tbmres->blockno)
elog(ERROR, "prefetch and main iterators are out of sync");
}
return;
}
if (node->prefetch_maximum > 0)
{
TBMSharedIterator *prefetch_iterator = node->shared_prefetch_iterator;
SpinLockAcquire(&pstate->mutex);
if (pstate->prefetch_pages > 0)
{
pstate->prefetch_pages--;
SpinLockRelease(&pstate->mutex);
}
else
{
/* Release the mutex before iterating */
SpinLockRelease(&pstate->mutex);
/*
* In case of shared mode, we can not ensure that the current
* blockno of the main iterator and that of the prefetch iterator
* are same. It's possible that whatever blockno we are
* prefetching will be processed by another process. Therefore,
* we don't validate the blockno here as we do in non-parallel
* case.
*/
if (prefetch_iterator)
tbm_shared_iterate(prefetch_iterator);
}
}
#endif /* USE_PREFETCH */
}
/*
* BitmapAdjustPrefetchTarget - Adjust the prefetch target
*
* Increase prefetch target if it's not yet at the max. Note that
* we will increase it to zero after fetching the very first
* page/tuple, then to one after the second tuple is fetched, then
* it doubles as later pages are fetched.
*/
static inline void
BitmapAdjustPrefetchTarget(BitmapHeapScanState *node)
{
#ifdef USE_PREFETCH
ParallelBitmapHeapState *pstate = node->pstate;
if (pstate == NULL)
{
if (node->prefetch_target >= node->prefetch_maximum)
/* don't increase any further */ ;
else if (node->prefetch_target >= node->prefetch_maximum / 2)
node->prefetch_target = node->prefetch_maximum;
else if (node->prefetch_target > 0)
node->prefetch_target *= 2;
else
node->prefetch_target++;
return;
}
/* Do an unlocked check first to save spinlock acquisitions. */
if (pstate->prefetch_target < node->prefetch_maximum)
{
SpinLockAcquire(&pstate->mutex);
if (pstate->prefetch_target >= node->prefetch_maximum)
/* don't increase any further */ ;
else if (pstate->prefetch_target >= node->prefetch_maximum / 2)
pstate->prefetch_target = node->prefetch_maximum;
else if (pstate->prefetch_target > 0)
pstate->prefetch_target *= 2;
else
pstate->prefetch_target++;
SpinLockRelease(&pstate->mutex);
}
#endif /* USE_PREFETCH */
}
/*
* BitmapPrefetch - Prefetch, if prefetch_pages are behind prefetch_target
*/
static inline void
BitmapPrefetch(BitmapHeapScanState *node, TableScanDesc scan)
{
#ifdef USE_PREFETCH
ParallelBitmapHeapState *pstate = node->pstate;
if (pstate == NULL)
{
TBMIterator *prefetch_iterator = node->prefetch_iterator;
if (prefetch_iterator)
{
while (node->prefetch_pages < node->prefetch_target)
{
TBMIterateResult *tbmpre = tbm_iterate(prefetch_iterator);
bool skip_fetch;
if (tbmpre == NULL)
{
/* No more pages to prefetch */
tbm_end_iterate(prefetch_iterator);
node->prefetch_iterator = NULL;
break;
}
node->prefetch_pages++;
/*
* If we expect not to have to actually read this heap page,
* skip this prefetch call, but continue to run the prefetch
* logic normally. (Would it be better not to increment
* prefetch_pages?)
*
* This depends on the assumption that the index AM will
* report the same recheck flag for this future heap page as
* it did for the current heap page; which is not a certainty
* but is true in many cases.
*/
skip_fetch = (node->can_skip_fetch &&
(node->tbmres ? !node->tbmres->recheck : false) &&
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
tbmpre->blockno,
&node->pvmbuffer));
if (!skip_fetch)
PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
}
}
return;
}
if (pstate->prefetch_pages < pstate->prefetch_target)
{
TBMSharedIterator *prefetch_iterator = node->shared_prefetch_iterator;
if (prefetch_iterator)
{
while (1)
{
TBMIterateResult *tbmpre;
bool do_prefetch = false;
bool skip_fetch;
/*
* Recheck under the mutex. If some other process has already
* done enough prefetching then we need not to do anything.
*/
SpinLockAcquire(&pstate->mutex);
if (pstate->prefetch_pages < pstate->prefetch_target)
{
pstate->prefetch_pages++;
do_prefetch = true;
}
SpinLockRelease(&pstate->mutex);
if (!do_prefetch)
return;
tbmpre = tbm_shared_iterate(prefetch_iterator);
if (tbmpre == NULL)
{
/* No more pages to prefetch */
tbm_end_shared_iterate(prefetch_iterator);
node->shared_prefetch_iterator = NULL;
break;
}
/* As above, skip prefetch if we expect not to need page */
skip_fetch = (node->can_skip_fetch &&
(node->tbmres ? !node->tbmres->recheck : false) &&
VM_ALL_VISIBLE(node->ss.ss_currentRelation,
tbmpre->blockno,
&node->pvmbuffer));
if (!skip_fetch)
PrefetchBuffer(scan->rs_rd, MAIN_FORKNUM, tbmpre->blockno);
}
}
}
#endif /* USE_PREFETCH */
}
/*
* BitmapHeapRecheck -- access method routine to recheck a tuple in EvalPlanQual
*/
static bool
BitmapHeapRecheck(BitmapHeapScanState *node, TupleTableSlot *slot)
{
ExprContext *econtext;
/*
* extract necessary information from index scan node
*/
econtext = node->ss.ps.ps_ExprContext;
/* Does the tuple meet the original qual conditions? */
econtext->ecxt_scantuple = slot;
return ExecQualAndReset(node->bitmapqualorig, econtext);
}
/* ----------------------------------------------------------------
* ExecBitmapHeapScan(node)
* ----------------------------------------------------------------
*/
static TupleTableSlot *
ExecBitmapHeapScan(PlanState *pstate)
{
BitmapHeapScanState *node = castNode(BitmapHeapScanState, pstate);
return ExecScan(&node->ss,
(ExecScanAccessMtd) BitmapHeapNext,
(ExecScanRecheckMtd) BitmapHeapRecheck);
}
/* ----------------------------------------------------------------
* ExecReScanBitmapHeapScan(node)
* ----------------------------------------------------------------
*/
void
ExecReScanBitmapHeapScan(BitmapHeapScanState *node)
{
PlanState *outerPlan = outerPlanState(node);
/* rescan to release any page pin */
table_rescan(node->ss.ss_currentScanDesc, NULL);
/* release bitmaps and buffers if any */
if (node->tbmiterator)
tbm_end_iterate(node->tbmiterator);
if (node->prefetch_iterator)
tbm_end_iterate(node->prefetch_iterator);
if (node->shared_tbmiterator)
tbm_end_shared_iterate(node->shared_tbmiterator);
if (node->shared_prefetch_iterator)
tbm_end_shared_iterate(node->shared_prefetch_iterator);
if (node->tbm)
tbm_free(node->tbm);
if (node->vmbuffer != InvalidBuffer)
ReleaseBuffer(node->vmbuffer);
if (node->pvmbuffer != InvalidBuffer)
ReleaseBuffer(node->pvmbuffer);
node->tbm = NULL;
node->tbmiterator = NULL;
node->tbmres = NULL;
node->prefetch_iterator = NULL;
node->initialized = false;
node->shared_tbmiterator = NULL;
node->shared_prefetch_iterator = NULL;
node->vmbuffer = InvalidBuffer;
node->pvmbuffer = InvalidBuffer;
ExecScanReScan(&node->ss);
/*
* if chgParam of subnode is not null then plan will be re-scanned by
* first ExecProcNode.
*/
if (outerPlan->chgParam == NULL)
ExecReScan(outerPlan);
}
/* ----------------------------------------------------------------
* ExecEndBitmapHeapScan
* ----------------------------------------------------------------
*/
void
ExecEndBitmapHeapScan(BitmapHeapScanState *node)
{
TableScanDesc scanDesc;
/*
* extract information from the node
*/
scanDesc = node->ss.ss_currentScanDesc;
/*
* Free the exprcontext
*/
ExecFreeExprContext(&node->ss.ps);
/*
* clear out tuple table slots
*/
if (node->ss.ps.ps_ResultTupleSlot)
ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
ExecClearTuple(node->ss.ss_ScanTupleSlot);
/*
* close down subplans
*/
ExecEndNode(outerPlanState(node));
/*
* release bitmaps and buffers if any
*/
if (node->tbmiterator)
tbm_end_iterate(node->tbmiterator);
if (node->prefetch_iterator)
tbm_end_iterate(node->prefetch_iterator);
if (node->tbm)
tbm_free(node->tbm);
if (node->shared_tbmiterator)
tbm_end_shared_iterate(node->shared_tbmiterator);
if (node->shared_prefetch_iterator)
tbm_end_shared_iterate(node->shared_prefetch_iterator);
if (node->vmbuffer != InvalidBuffer)
ReleaseBuffer(node->vmbuffer);
if (node->pvmbuffer != InvalidBuffer)
ReleaseBuffer(node->pvmbuffer);
/*
* close heap scan
*/
table_endscan(scanDesc);
}
/* ----------------------------------------------------------------
* ExecInitBitmapHeapScan
*
* Initializes the scan's state information.
* ----------------------------------------------------------------
*/
BitmapHeapScanState *
ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
{
BitmapHeapScanState *scanstate;
Relation currentRelation;
int io_concurrency;
/* check for unsupported flags */
Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
/*
* Assert caller didn't ask for an unsafe snapshot --- see comments at
* head of file.
*/
Assert(IsMVCCSnapshot(estate->es_snapshot));
/*
* create state structure
*/
scanstate = makeNode(BitmapHeapScanState);
scanstate->ss.ps.plan = (Plan *) node;
scanstate->ss.ps.state = estate;
scanstate->ss.ps.ExecProcNode = ExecBitmapHeapScan;
scanstate->tbm = NULL;
scanstate->tbmiterator = NULL;
scanstate->tbmres = NULL;
scanstate->return_empty_tuples = 0;
scanstate->vmbuffer = InvalidBuffer;
scanstate->pvmbuffer = InvalidBuffer;
scanstate->exact_pages = 0;
scanstate->lossy_pages = 0;
scanstate->prefetch_iterator = NULL;
scanstate->prefetch_pages = 0;
scanstate->prefetch_target = 0;
/* may be updated below */
scanstate->prefetch_maximum = target_prefetch_pages;
scanstate->pscan_len = 0;
scanstate->initialized = false;
scanstate->shared_tbmiterator = NULL;
scanstate->shared_prefetch_iterator = NULL;
scanstate->pstate = NULL;
/*
* We can potentially skip fetching heap pages if we do not need any
* columns of the table, either for checking non-indexable quals or for
* returning data. This test is a bit simplistic, as it checks the
* stronger condition that there's no qual or return tlist at all. But in
* most cases it's probably not worth working harder than that.
*/
scanstate->can_skip_fetch = (node->scan.plan.qual == NIL &&
node->scan.plan.targetlist == NIL);
/*
* Miscellaneous initialization
*
* create expression context for node
*/
ExecAssignExprContext(estate, &scanstate->ss.ps);
/*
* open the scan relation
*/
currentRelation = ExecOpenScanRelation(estate, node->scan.scanrelid, eflags);
/*
* initialize child nodes
*/
outerPlanState(scanstate) = ExecInitNode(outerPlan(node), estate, eflags);
/*
* get the scan type from the relation descriptor.
*/
ExecInitScanTupleSlot(estate, &scanstate->ss,
RelationGetDescr(currentRelation),
table_slot_callbacks(currentRelation));
/*
* Initialize result type and projection.
*/
ExecInitResultTypeTL(&scanstate->ss.ps);
ExecAssignScanProjectionInfo(&scanstate->ss);
/*
* initialize child expressions
*/
scanstate->ss.ps.qual =
ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
scanstate->bitmapqualorig =
ExecInitQual(node->bitmapqualorig, (PlanState *) scanstate);
/*
* Determine the maximum for prefetch_target. If the tablespace has a
* specific IO concurrency set, use that to compute the corresponding
* maximum value; otherwise, we already initialized to the value computed
* by the GUC machinery.
*/
io_concurrency =
get_tablespace_io_concurrency(currentRelation->rd_rel->reltablespace);
if (io_concurrency != effective_io_concurrency)
{
double maximum;
if (ComputeIoConcurrency(io_concurrency, &maximum))
scanstate->prefetch_maximum = rint(maximum);
}
scanstate->ss.ss_currentRelation = currentRelation;
scanstate->ss.ss_currentScanDesc = table_beginscan_bm(currentRelation,
estate->es_snapshot,
0,
NULL);
/*
* all done.
*/
return scanstate;
}
/*----------------
* BitmapShouldInitializeSharedState
*
* The first process to come here and see the state to the BM_INITIAL
* will become the leader for the parallel bitmap scan and will be
* responsible for populating the TIDBitmap. The other processes will
* be blocked by the condition variable until the leader wakes them up.
* ---------------
*/
static bool
BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate)
{
SharedBitmapState state;
while (1)
{
SpinLockAcquire(&pstate->mutex);
state = pstate->state;
if (pstate->state == BM_INITIAL)
pstate->state = BM_INPROGRESS;
SpinLockRelease(&pstate->mutex);
/* Exit if bitmap is done, or if we're the leader. */
if (state != BM_INPROGRESS)
break;
/* Wait for the leader to wake us up. */
ConditionVariableSleep(&pstate->cv, WAIT_EVENT_PARALLEL_BITMAP_SCAN);
}
ConditionVariableCancelSleep();
return (state == BM_INITIAL);
}
/* ----------------------------------------------------------------
* ExecBitmapHeapEstimate
*
* Compute the amount of space we'll need in the parallel
* query DSM, and inform pcxt->estimator about our needs.
* ----------------------------------------------------------------
*/
void
ExecBitmapHeapEstimate(BitmapHeapScanState *node,
ParallelContext *pcxt)
{
EState *estate = node->ss.ps.state;
node->pscan_len = add_size(offsetof(ParallelBitmapHeapState,
phs_snapshot_data),
EstimateSnapshotSpace(estate->es_snapshot));
shm_toc_estimate_chunk(&pcxt->estimator, node->pscan_len);
shm_toc_estimate_keys(&pcxt->estimator, 1);
}
/* ----------------------------------------------------------------
* ExecBitmapHeapInitializeDSM
*
* Set up a parallel bitmap heap scan descriptor.
* ----------------------------------------------------------------
*/
void
ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
ParallelContext *pcxt)
{
ParallelBitmapHeapState *pstate;
EState *estate = node->ss.ps.state;
dsa_area *dsa = node->ss.ps.state->es_query_dsa;
/* If there's no DSA, there are no workers; initialize nothing. */
if (dsa == NULL)
return;
pstate = shm_toc_allocate(pcxt->toc, node->pscan_len);
pstate->tbmiterator = 0;
pstate->prefetch_iterator = 0;
/* Initialize the mutex */
SpinLockInit(&pstate->mutex);
pstate->prefetch_pages = 0;
pstate->prefetch_target = 0;
pstate->state = BM_INITIAL;
ConditionVariableInit(&pstate->cv);
SerializeSnapshot(estate->es_snapshot, pstate->phs_snapshot_data);
shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pstate);
node->pstate = pstate;
}
/* ----------------------------------------------------------------
* ExecBitmapHeapReInitializeDSM
*
* Reset shared state before beginning a fresh scan.
* ----------------------------------------------------------------
*/
void
ExecBitmapHeapReInitializeDSM(BitmapHeapScanState *node,
ParallelContext *pcxt)
{
ParallelBitmapHeapState *pstate = node->pstate;
dsa_area *dsa = node->ss.ps.state->es_query_dsa;
/* If there's no DSA, there are no workers; do nothing. */
if (dsa == NULL)
return;
pstate->state = BM_INITIAL;
if (DsaPointerIsValid(pstate->tbmiterator))
tbm_free_shared_area(dsa, pstate->tbmiterator);
if (DsaPointerIsValid(pstate->prefetch_iterator))
tbm_free_shared_area(dsa, pstate->prefetch_iterator);
pstate->tbmiterator = InvalidDsaPointer;
pstate->prefetch_iterator = InvalidDsaPointer;
}
/* ----------------------------------------------------------------
* ExecBitmapHeapInitializeWorker
*
* Copy relevant information from TOC into planstate.
* ----------------------------------------------------------------
*/
void
ExecBitmapHeapInitializeWorker(BitmapHeapScanState *node,
ParallelWorkerContext *pwcxt)
{
ParallelBitmapHeapState *pstate;
Snapshot snapshot;
Assert(node->ss.ps.state->es_query_dsa != NULL);
pstate = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
node->pstate = pstate;
snapshot = RestoreSnapshot(pstate->phs_snapshot_data);
table_scan_update_snapshot(node->ss.ss_currentScanDesc, snapshot);
}
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