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Show Parallel Bitmap Heap Scan worker stats in EXPLAIN ANALYZE

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Nodes like Memoize report the cache stats for each parallel worker, so it
makes sense to show the exact and lossy pages in Parallel Bitmap Heap Scan
in a similar way.  Likewise, Sort shows the method and memory used for
each worker.

There was some discussion on whether the leader stats should include the
totals for each parallel worker or not.  I did some analysis on this to
see what other parallel node types do and it seems only Parallel Hash does
anything like this.  All the rest, per what's supported by
ExecParallelRetrieveInstrumentation() are consistent with each other.

Author: David Geier <geidav.pg@gmail.com>
Author: Heikki Linnakangas <hlinnaka@iki.fi>
Author: Donghang Lin <donghanglin@gmail.com>
Author: Alena Rybakina <lena.ribackina@yandex.ru>
Author: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Dmitry Dolgov <9erthalion6@gmail.com>
Reviewed-by: Michael Christofides <michael@pgmustard.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Tomas Vondra <tomas.vondra@enterprisedb.com>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Donghang Lin <donghanglin@gmail.com>
Reviewed-by: Masahiro Ikeda <Masahiro.Ikeda@nttdata.com>
Discussion: https://postgr.es/m/b3d80961-c2e5-38cc-6a32-61886cdf766d%40gmail.com
This commit is contained in:
David Rowley
2024-07-09 12:15:47 +12:00
parent e41f713097
commit 5a1e6df3b8
6 changed files with 181 additions and 23 deletions
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105
src/backend/executor/nodeBitmapHeapscan.c
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@@ -236,9 +236,9 @@ BitmapHeapNext(BitmapHeapScanState *node)
valid_block = table_scan_bitmap_next_block(scan, tbmres);
if (tbmres->ntuples >= 0)
node->exact_pages++;
node->stats.exact_pages++;
else
node->lossy_pages++;
node->stats.lossy_pages++;
if (!valid_block)
{
@@ -627,6 +627,29 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node)
{
TableScanDesc scanDesc;
/*
* When ending a parallel worker, copy the statistics gathered by the
* worker back into shared memory so that it can be picked up by the main
* process to report in EXPLAIN ANALYZE.
*/
if (node->sinstrument != NULL && IsParallelWorker())
{
BitmapHeapScanInstrumentation *si;
Assert(ParallelWorkerNumber <= node->sinstrument->num_workers);
si = &node->sinstrument->sinstrument[ParallelWorkerNumber];
/*
* Here we accumulate the stats rather than performing memcpy on
* node->stats into si. When a Gather/GatherMerge node finishes it
* will perform planner shutdown on the workers. On rescan it will
* spin up new workers which will have a new BitmapHeapScanState and
* zeroed stats.
*/
si->exact_pages += node->stats.exact_pages;
si->lossy_pages += node->stats.lossy_pages;
}
/*
* extract information from the node
*/
@@ -694,8 +717,10 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
scanstate->tbmiterator = NULL;
scanstate->tbmres = NULL;
scanstate->pvmbuffer = InvalidBuffer;
scanstate->exact_pages = 0;
scanstate->lossy_pages = 0;
/* Zero the statistics counters */
memset(&scanstate->stats, 0, sizeof(BitmapHeapScanInstrumentation));
scanstate->prefetch_iterator = NULL;
scanstate->prefetch_pages = 0;
scanstate->prefetch_target = 0;
@@ -803,7 +828,18 @@ void
ExecBitmapHeapEstimate(BitmapHeapScanState *node,
ParallelContext *pcxt)
{
shm_toc_estimate_chunk(&pcxt->estimator, sizeof(ParallelBitmapHeapState));
Size size;
size = MAXALIGN(sizeof(ParallelBitmapHeapState));
/* account for instrumentation, if required */
if (node->ss.ps.instrument && pcxt->nworkers > 0)
{
size = add_size(size, offsetof(SharedBitmapHeapInstrumentation, sinstrument));
size = add_size(size, mul_size(pcxt->nworkers, sizeof(BitmapHeapScanInstrumentation)));
}
shm_toc_estimate_chunk(&pcxt->estimator, size);
shm_toc_estimate_keys(&pcxt->estimator, 1);
}
@@ -818,13 +854,27 @@ ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
ParallelContext *pcxt)
{
ParallelBitmapHeapState *pstate;
SharedBitmapHeapInstrumentation *sinstrument = NULL;
dsa_area *dsa = node->ss.ps.state->es_query_dsa;
char *ptr;
Size size;
/* If there's no DSA, there are no workers; initialize nothing. */
if (dsa == NULL)
return;
pstate = shm_toc_allocate(pcxt->toc, sizeof(ParallelBitmapHeapState));
size = MAXALIGN(sizeof(ParallelBitmapHeapState));
if (node->ss.ps.instrument && pcxt->nworkers > 0)
{
size = add_size(size, offsetof(SharedBitmapHeapInstrumentation, sinstrument));
size = add_size(size, mul_size(pcxt->nworkers, sizeof(BitmapHeapScanInstrumentation)));
}
ptr = shm_toc_allocate(pcxt->toc, size);
pstate = (ParallelBitmapHeapState *) ptr;
ptr += MAXALIGN(sizeof(ParallelBitmapHeapState));
if (node->ss.ps.instrument && pcxt->nworkers > 0)
sinstrument = (SharedBitmapHeapInstrumentation *) ptr;
pstate->tbmiterator = 0;
pstate->prefetch_iterator = 0;
@@ -837,8 +887,18 @@ ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
ConditionVariableInit(&pstate->cv);
if (sinstrument)
{
sinstrument->num_workers = pcxt->nworkers;
/* ensure any unfilled slots will contain zeroes */
memset(sinstrument->sinstrument, 0,
pcxt->nworkers * sizeof(BitmapHeapScanInstrumentation));
}
shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pstate);
node->pstate = pstate;
node->sinstrument = sinstrument;
}
/* ----------------------------------------------------------------
@@ -880,10 +940,37 @@ void
ExecBitmapHeapInitializeWorker(BitmapHeapScanState *node,
ParallelWorkerContext *pwcxt)
{
ParallelBitmapHeapState *pstate;
char *ptr;
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;
ptr = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
node->pstate = (ParallelBitmapHeapState *) ptr;
ptr += MAXALIGN(sizeof(ParallelBitmapHeapState));
if (node->ss.ps.instrument)
node->sinstrument = (SharedBitmapHeapInstrumentation *) ptr;
}
/* ----------------------------------------------------------------
* ExecBitmapHeapRetrieveInstrumentation
*
* Transfer bitmap heap scan statistics from DSM to private memory.
* ----------------------------------------------------------------
*/
void
ExecBitmapHeapRetrieveInstrumentation(BitmapHeapScanState *node)
{
SharedBitmapHeapInstrumentation *sinstrument = node->sinstrument;
Size size;
if (sinstrument == NULL)
return;
size = offsetof(SharedBitmapHeapInstrumentation, sinstrument)
+ sinstrument->num_workers * sizeof(BitmapHeapScanInstrumentation);
node->sinstrument = palloc(size);
memcpy(node->sinstrument, sinstrument, size);
}