public inbox for [email protected]
help / color / mirror / Atom feedFrom: Donghang Lin <[email protected]>
To: Melanie Plageman <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Dilip Kumar <[email protected]>
Cc: David Geier <[email protected]>
Cc: PostgreSQL Developers <[email protected]>
Cc: [email protected]
Subject: Re: Parallel Bitmap Heap Scan reports per-worker stats in EXPLAIN ANALYZE
Date: Wed, 27 Mar 2024 00:03:08 -0700
Message-ID: <CAA=D8a1G5CgvdWLd5_VCEc5Sa3rgJftcGfTEvYqG1HnjMBQmpA@mail.gmail.com> (raw)
In-Reply-To: <CAAKRu_YjBPfGp85ehY1t9NN=R9pB9k=6rztaeVkAm-OeTqUK4g@mail.gmail.com>
References: <[email protected]>
<CAFiTN-v1yDvU=X+hwfJ+55=sbgDj=_kuvbduEG-F7=BjpWcnuw@mail.gmail.com>
<[email protected]>
<CAA=D8a1ZGWTk0RDH-LyU==RsE-217T29eprS-NBhyj+eLHyRrQ@mail.gmail.com>
<CAAKRu_YjBPfGp85ehY1t9NN=R9pB9k=6rztaeVkAm-OeTqUK4g@mail.gmail.com>
On Mon, Mar 25, 2024 at 2:11 PM Melanie Plageman <[email protected]>
wrote:
> As for whether or not per-worker stats should be displayed by default
> or only with VERBOSE, it sounds like there are two different
> precedents. I don't have a strong feeling one way or the other.
> Whichever is most consistent.
> Donghang, could you list again which plan nodes and explain options
> always print per-worker stats and which only do with the VERBOSE
> option?
I took a look at explain.c where workers info is printed out.
These works for every parallel aware nodes:
Buffers stats print for workers with VERBOSE and BUFFERS
WAL stats print for workers with VERBOSE and WAL
JIT stats print for workers with VERBOSE and COSTS
Timing print for workers with VERBOSE and TIMING
Rows and loops print for workers with VERBOSE
Some specific nodes:
Sort / Incremental Sort / Hash / HashAggregate / Memorize and Bitmap Heap
Scan (this patch) nodes
always print their specific stats for workers.
> I did some logging and I do see workers with
> counts of lossy/exact not making it into the final count. I haven't
> had time to debug more, but it is worth looking into.
Indeed, rescan overrides previous scan stats in workers.
Attach v5 with v4 plus the fix to aggregate the counts.
Regards,
Donghang Lin
(ServiceNow)
Attachments:
[application/octet-stream] v5-0001-Parallel-Bitmap-Heap-Scan-reports-per-worker-stat.patch (11.4K, 3-v5-0001-Parallel-Bitmap-Heap-Scan-reports-per-worker-stat.patch)
download | inline diff:
From 9894cc5006fc7dbb2e80a19bed2c7d9885b24002 Mon Sep 17 00:00:00 2001
From: David Geier <[email protected]>
Date: Tue, 8 Nov 2022 19:40:31 +0100
Subject: [PATCH v5] Parallel Bitmap Heap Scan reports per-worker stats
Similarly to other nodes (e.g. hash join, sort, memoize),
Bitmap Heap Scan now reports per-worker stats in the EXPLAIN
ANALYZE output. Previously only the heap blocks stats for the
leader were reported which was incomplete in parallel scans.
Discussion: https://www.postgresql.org/message-id/flat/b3d80961-c2e5-38cc-6a32-61886cdf766d%40gmail.com
---
src/backend/commands/explain.c | 45 +++++++++--
src/backend/executor/execParallel.c | 3 +
src/backend/executor/nodeBitmapHeapscan.c | 95 ++++++++++++++++++++---
src/include/executor/nodeBitmapHeapscan.h | 1 +
src/include/nodes/execnodes.h | 33 +++++++-
5 files changed, 159 insertions(+), 18 deletions(-)
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 926d70afaf..02251994c6 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -3467,26 +3467,57 @@ show_hashagg_info(AggState *aggstate, ExplainState *es)
static void
show_tidbitmap_info(BitmapHeapScanState *planstate, ExplainState *es)
{
+ Assert(es->analyze);
+
if (es->format != EXPLAIN_FORMAT_TEXT)
{
ExplainPropertyInteger("Exact Heap Blocks", NULL,
- planstate->exact_pages, es);
+ planstate->stats.exact_pages, es);
ExplainPropertyInteger("Lossy Heap Blocks", NULL,
- planstate->lossy_pages, es);
+ planstate->stats.lossy_pages, es);
}
else
{
- if (planstate->exact_pages > 0 || planstate->lossy_pages > 0)
+ if (planstate->stats.exact_pages > 0 || planstate->stats.lossy_pages > 0)
{
ExplainIndentText(es);
appendStringInfoString(es->str, "Heap Blocks:");
- if (planstate->exact_pages > 0)
- appendStringInfo(es->str, " exact=%ld", planstate->exact_pages);
- if (planstate->lossy_pages > 0)
- appendStringInfo(es->str, " lossy=%ld", planstate->lossy_pages);
+ if (planstate->stats.exact_pages > 0)
+ appendStringInfo(es->str, " exact=%ld", planstate->stats.exact_pages);
+ if (planstate->stats.lossy_pages > 0)
+ appendStringInfo(es->str, " lossy=%ld", planstate->stats.lossy_pages);
appendStringInfoChar(es->str, '\n');
}
}
+
+ if (planstate->pstate != NULL)
+ {
+ for (int n = 0; n < planstate->sinstrument->num_workers; n++)
+ {
+ BitmapHeapScanInstrumentation *si = &planstate->sinstrument->sinstrument[n];
+
+ if (si->exact_pages == 0 && si->lossy_pages == 0)
+ continue;
+
+ if (es->workers_state)
+ ExplainOpenWorker(n, es);
+
+ if (es->format == EXPLAIN_FORMAT_TEXT)
+ {
+ ExplainIndentText(es);
+ appendStringInfo(es->str, "Heap Blocks: exact=%ld lossy=%ld\n",
+ si->exact_pages, si->lossy_pages);
+ }
+ else
+ {
+ ExplainPropertyInteger("Exact Heap Blocks", NULL, si->exact_pages, es);
+ ExplainPropertyInteger("Lossy Heap Blocks", NULL, si->lossy_pages, es);
+ }
+
+ if (es->workers_state)
+ ExplainCloseWorker(n, es);
+ }
+ }
}
/*
diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c
index 8c53d1834e..bfb3419efb 100644
--- a/src/backend/executor/execParallel.c
+++ b/src/backend/executor/execParallel.c
@@ -1076,6 +1076,9 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate,
case T_MemoizeState:
ExecMemoizeRetrieveInstrumentation((MemoizeState *) planstate);
break;
+ case T_BitmapHeapScanState:
+ ExecBitmapHeapRetrieveInstrumentation((BitmapHeapScanState *) planstate);
+ break;
default:
break;
}
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index cee7f45aab..68b71d82cd 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -205,9 +205,9 @@ BitmapHeapNext(BitmapHeapScanState *node)
BitmapAdjustPrefetchIterator(node, tbmres);
if (tbmres->ntuples >= 0)
- node->exact_pages++;
+ node->stats.exact_pages++;
else
- node->lossy_pages++;
+ node->stats.lossy_pages++;
/*
* We can skip fetching the heap page if we don't need any fields
@@ -647,6 +647,19 @@ 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())
+ {
+ Assert(ParallelWorkerNumber <= node->sinstrument->num_workers);
+ BitmapHeapScanInstrumentation *si = &node->sinstrument->sinstrument[ParallelWorkerNumber];
+ si->exact_pages += node->stats.exact_pages;
+ si->lossy_pages += node->stats.lossy_pages;
+ }
+
/*
* extract information from the node
*/
@@ -716,8 +729,8 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
scanstate->return_empty_tuples = 0;
scanstate->vmbuffer = InvalidBuffer;
scanstate->pvmbuffer = InvalidBuffer;
- scanstate->exact_pages = 0;
- scanstate->lossy_pages = 0;
+ scanstate->stats.exact_pages = 0;
+ scanstate->stats.lossy_pages = 0;
scanstate->prefetch_iterator = NULL;
scanstate->prefetch_pages = 0;
scanstate->prefetch_target = 0;
@@ -840,7 +853,22 @@ void
ExecBitmapHeapEstimate(BitmapHeapScanState *node,
ParallelContext *pcxt)
{
- shm_toc_estimate_chunk(&pcxt->estimator, sizeof(ParallelBitmapHeapState));
+ Size size;
+
+ /*
+ * We store ParallelBitmapHeapState followed by
+ * SharedBitmapHeapInstrumentationInfo in the same shmem chunk.
+ */
+ size = MAXALIGN(sizeof(ParallelBitmapHeapState));
+
+ /* don't need this if not instrumenting or no workers */
+ 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);
}
@@ -855,13 +883,27 @@ 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;
@@ -874,8 +916,16 @@ ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
ConditionVariableInit(&pstate->cv);
+ /* ensure any unfilled slots will contain zeroes */
+ if (sinstrument)
+ {
+ sinstrument->num_workers = pcxt->nworkers;
+ 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;
}
/* ----------------------------------------------------------------
@@ -917,10 +967,37 @@ 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);
}
diff --git a/src/include/executor/nodeBitmapHeapscan.h b/src/include/executor/nodeBitmapHeapscan.h
index ea003a9caa..446a664590 100644
--- a/src/include/executor/nodeBitmapHeapscan.h
+++ b/src/include/executor/nodeBitmapHeapscan.h
@@ -28,5 +28,6 @@ extern void ExecBitmapHeapReInitializeDSM(BitmapHeapScanState *node,
ParallelContext *pcxt);
extern void ExecBitmapHeapInitializeWorker(BitmapHeapScanState *node,
ParallelWorkerContext *pwcxt);
+extern void ExecBitmapHeapRetrieveInstrumentation(BitmapHeapScanState *node);
#endif /* NODEBITMAPHEAPSCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 1774c56ae3..8306e0c47b 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1735,6 +1735,12 @@ typedef struct BitmapIndexScanState
struct IndexScanDescData *biss_ScanDesc;
} BitmapIndexScanState;
+typedef struct BitmapHeapScanInstrumentation
+{
+ long lossy_pages;
+ long exact_pages;
+} BitmapHeapScanInstrumentation;
+
/* ----------------
* SharedBitmapState information
*
@@ -1778,6 +1784,20 @@ typedef struct ParallelBitmapHeapState
ConditionVariable cv;
} ParallelBitmapHeapState;
+/* ----------------
+ * Instrumentation data for a parallel bitmap heap scan.
+ *
+ * During a parallel bitmap heap scan, this lives in shared memory. At the
+ * end, each worker copies their own stats to the right slot. Finally, the
+ * leader copies the data to its local memory
+ * ----------------
+ */
+typedef struct SharedBitmapHeapInstrumentation
+{
+ int num_workers;
+ BitmapHeapScanInstrumentation sinstrument[FLEXIBLE_ARRAY_MEMBER];
+} SharedBitmapHeapInstrumentation;
+
/* ----------------
* BitmapHeapScanState information
*
@@ -1812,8 +1832,6 @@ typedef struct BitmapHeapScanState
int return_empty_tuples;
Buffer vmbuffer;
Buffer pvmbuffer;
- long exact_pages;
- long lossy_pages;
TBMIterator *prefetch_iterator;
int prefetch_pages;
int prefetch_target;
@@ -1822,6 +1840,17 @@ typedef struct BitmapHeapScanState
TBMSharedIterator *shared_tbmiterator;
TBMSharedIterator *shared_prefetch_iterator;
ParallelBitmapHeapState *pstate;
+
+ /*
+ * In a parallelized bitmap heap scan, each worker sets their
+ * instrumentaton data in pstate->sinstrument at the end. The leader
+ * copies the shared-memory info back to local storage before DSM
+ * shutdown, and stores it here in 'instrument'. It remains NULL in
+ * workers and in non-parallel scans.
+ */
+ SharedBitmapHeapInstrumentation *sinstrument;
+
+ BitmapHeapScanInstrumentation stats;
} BitmapHeapScanState;
/* ----------------
--
2.40.1
view thread (23+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: Parallel Bitmap Heap Scan reports per-worker stats in EXPLAIN ANALYZE
In-Reply-To: <CAA=D8a1G5CgvdWLd5_VCEc5Sa3rgJftcGfTEvYqG1HnjMBQmpA@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox