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Commit72567f6

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Try again to fix accumulation of parallel worker instrumentation.
When a Gather or Gather Merge node is started and stopped multipletimes, accumulate instrumentation data only once, at the end, insteadof after each execution, to avoid recording inflated totals.Commit778e78a, the previous attemptat a fix, instead reset the state after every execution, which workedfor the general instrumentation data but had problems for the additionalinstrumentation specific to Sort and Hash nodes.Report by hubert depesz lubaczewski. Analysis and fix by Amit Kapila,following a design proposal from Thomas Munro, with a comment tweakby me.Discussion:http://postgr.es/m/20171127175631.GA405@depesz.com
1 parentdb2ee07 commit72567f6

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3 files changed

+38
-10
lines changed

3 files changed

+38
-10
lines changed

‎src/backend/executor/execParallel.c

Lines changed: 10 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -723,7 +723,7 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate,
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/*
725725
* Finish parallel execution. We wait for parallel workers to finish, and
726-
* accumulate their buffer usage and instrumentation.
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* accumulate their buffer usage.
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*/
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void
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ExecParallelFinish(ParallelExecutorInfo*pei)
@@ -769,23 +769,23 @@ ExecParallelFinish(ParallelExecutorInfo *pei)
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for (i=0;i<nworkers;i++)
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InstrAccumParallelQuery(&pei->buffer_usage[i]);
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772-
/* Finally, accumulate instrumentation, if any. */
773-
if (pei->instrumentation)
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ExecParallelRetrieveInstrumentation(pei->planstate,
775-
pei->instrumentation);
776-
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pei->finished= true;
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}
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780775
/*
781-
*Clean up whatever ParallelExecutorInfo resources still exist after
782-
* ExecParallelFinish. We separate these routines because someone might
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* want to examine the contents of the DSM after ExecParallelFinish and
784-
* before calling this routine.
776+
*Accumulate instrumentation, and then clean up whatever ParallelExecutorInfo
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*resources still exist afterExecParallelFinish. We separate these
778+
*routines because someone mightwant to examine the contents of the DSM
779+
*after ExecParallelFinish andbefore calling this routine.
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*/
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void
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ExecParallelCleanup(ParallelExecutorInfo*pei)
788783
{
784+
/* Accumulate instrumentation, if any. */
785+
if (pei->instrumentation)
786+
ExecParallelRetrieveInstrumentation(pei->planstate,
787+
pei->instrumentation);
788+
789789
if (pei->area!=NULL)
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{
791791
dsa_detach(pei->area);

‎src/test/regress/expected/select_parallel.out

Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -300,7 +300,28 @@ select count(*) from bmscantest where a>1;
300300
99999
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(1 row)
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-- test accumulation of stats for parallel nodes
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reset enable_seqscan;
305+
alter table tenk2 set (parallel_workers = 0);
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explain (analyze, timing off, summary off, costs off)
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select count(*) from tenk1, tenk2 where tenk1.hundred > 1
308+
and tenk2.thousand=0;
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QUERY PLAN
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--------------------------------------------------------------------------
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Aggregate (actual rows=1 loops=1)
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-> Nested Loop (actual rows=98000 loops=1)
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-> Seq Scan on tenk2 (actual rows=10 loops=1)
314+
Filter: (thousand = 0)
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Rows Removed by Filter: 9990
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-> Gather (actual rows=9800 loops=10)
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Workers Planned: 4
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Workers Launched: 4
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-> Parallel Seq Scan on tenk1 (actual rows=1960 loops=50)
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Filter: (hundred > 1)
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Rows Removed by Filter: 40
322+
(11 rows)
323+
324+
alter table tenk2 reset (parallel_workers);
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reset enable_indexscan;
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reset enable_hashjoin;
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reset enable_mergejoin;

‎src/test/regress/sql/select_parallel.sql

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -116,7 +116,14 @@ insert into bmscantest select r, 'fooooooooooooooooooooooooooooooooooooooooooooo
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createindexi_bmtestON bmscantest(a);
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selectcount(*)from bmscantestwhere a>1;
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119+
-- test accumulation of stats for parallel nodes
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reset enable_seqscan;
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altertable tenk2set (parallel_workers=0);
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explain (analyze, timing off, summary off, costs off)
123+
selectcount(*)from tenk1, tenk2wheretenk1.hundred>1
124+
andtenk2.thousand=0;
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altertable tenk2 reset (parallel_workers);
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reset enable_indexscan;
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reset enable_hashjoin;
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reset enable_mergejoin;

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