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Skip setting up shared instrumentation for Hash node if not needed.

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We don't need to set up the shared space for hash join instrumentation data
if instrumentation hasn't been requested.  Let's follow the example of the
similar Sort node code and save a few cycles by skipping that when we can.

This reverts commit d59ff4ab3 and instead allows us to use the safer choice
of passing noError = false to shm_toc_lookup in ExecHashInitializeWorker,
since if we reach that call there should be a TOC entry to be found.

Thomas Munro

Discussion: https://postgr.es/m/E1ehkoZ-0005uW-43%40gemulon.postgresql.org
This commit is contained in:
Tom Lane 2018-02-04 22:14:07 -05:00
parent ad14919ac9
commit 05d0f13f07
1 changed files with 17 additions and 6 deletions
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23
src/backend/executor/nodeHash.c
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@ -2549,6 +2549,10 @@ ExecHashEstimate(HashState *node, ParallelContext *pcxt)
{
size_t size;
/* don't need this if not instrumenting or no workers */
if (!node->ps.instrument || pcxt->nworkers == 0)
return;
size = mul_size(pcxt->nworkers, sizeof(HashInstrumentation));
size = add_size(size, offsetof(SharedHashInfo, hinstrument));
shm_toc_estimate_chunk(&pcxt->estimator, size);
@ -2564,6 +2568,10 @@ ExecHashInitializeDSM(HashState *node, ParallelContext *pcxt)
{
size_t size;
/* don't need this if not instrumenting or no workers */
if (!node->ps.instrument || pcxt->nworkers == 0)
return;
size = offsetof(SharedHashInfo, hinstrument) +
pcxt->nworkers * sizeof(HashInstrumentation);
node->shared_info = (SharedHashInfo *) shm_toc_allocate(pcxt->toc, size);
@ -2582,13 +2590,13 @@ ExecHashInitializeWorker(HashState *node, ParallelWorkerContext *pwcxt)
{
SharedHashInfo *shared_info;
/* might not be there ... */
/* don't need this if not instrumenting */
if (!node->ps.instrument)
return;
shared_info = (SharedHashInfo *)
shm_toc_lookup(pwcxt->toc, node->ps.plan->plan_node_id, true);
if (shared_info)
node->hinstrument = &shared_info->hinstrument[ParallelWorkerNumber];
else
node->hinstrument = NULL;
shm_toc_lookup(pwcxt->toc, node->ps.plan->plan_node_id, false);
node->hinstrument = &shared_info->hinstrument[ParallelWorkerNumber];
}
/*
@ -2614,6 +2622,9 @@ ExecHashRetrieveInstrumentation(HashState *node)
SharedHashInfo *shared_info = node->shared_info;
size_t size;
if (shared_info == NULL)
return;
/* Replace node->shared_info with a copy in backend-local memory. */
size = offsetof(SharedHashInfo, hinstrument) +
shared_info->num_workers * sizeof(HashInstrumentation);