From: Michael Paquier <michael@paquier.xyz>
Date: Tue, 8 Oct 2024 23:07:48 +0000 (+0900)
Subject: Introduce two fields in EState to track parallel worker activity
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=de3a2ea3b264a5625cda6d8968f75e9bfb4dbdcb;p=users%2Fc2main%2Fpostgres.git

Introduce two fields in EState to track parallel worker activity

These fields can be set by executor nodes to record how many parallel
workers were planned to be launched and how many of them have been
actually launched within the number initially planned.  This data is
able to give an approximation of the parallel worker draught a system
is facing, making easier the tuning of related configuration parameters.

These fields will be used by some follow-up patches to populate other
parts of the system with their data.

Author: Guillaume Lelarge, Benoit Lobréau
Discussion: https://postgr.es/m/783bc7f7-659a-42fa-99dd-ee0565644e25@dalibo.com
Discussion: https://postgr.es/m/CAECtzeWtTGOK0UgKXdDGpfTVSa5bd_VbUt6K6xn8P7X+_dZqKw@mail.gmail.com
---

diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 5737f9f4eb..6712302ec8 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -158,6 +158,8 @@ CreateExecutorState(void)
 	estate->es_sourceText = NULL;
 
 	estate->es_use_parallel_mode = false;
+	estate->es_parallel_workers_to_launch = 0;
+	estate->es_parallel_workers_launched = 0;
 
 	estate->es_jit_flags = 0;
 	estate->es_jit = NULL;
diff --git a/src/backend/executor/nodeGather.c b/src/backend/executor/nodeGather.c
index 5d4ffe989c..7f7edc7f9f 100644
--- a/src/backend/executor/nodeGather.c
+++ b/src/backend/executor/nodeGather.c
@@ -182,6 +182,13 @@ ExecGather(PlanState *pstate)
 			/* We save # workers launched for the benefit of EXPLAIN */
 			node->nworkers_launched = pcxt->nworkers_launched;
 
+			/*
+			 * Count number of workers originally wanted and actually
+			 * launched.
+			 */
+			estate->es_parallel_workers_to_launch += pcxt->nworkers_to_launch;
+			estate->es_parallel_workers_launched += pcxt->nworkers_launched;
+
 			/* Set up tuple queue readers to read the results. */
 			if (pcxt->nworkers_launched > 0)
 			{
diff --git a/src/backend/executor/nodeGatherMerge.c b/src/backend/executor/nodeGatherMerge.c
index 45f6017c29..bc99c0b448 100644
--- a/src/backend/executor/nodeGatherMerge.c
+++ b/src/backend/executor/nodeGatherMerge.c
@@ -223,6 +223,13 @@ ExecGatherMerge(PlanState *pstate)
 			/* We save # workers launched for the benefit of EXPLAIN */
 			node->nworkers_launched = pcxt->nworkers_launched;
 
+			/*
+			 * Count number of workers originally wanted and actually
+			 * launched.
+			 */
+			estate->es_parallel_workers_to_launch += pcxt->nworkers_to_launch;
+			estate->es_parallel_workers_launched += pcxt->nworkers_launched;
+
 			/* Set up tuple queue readers to read the results. */
 			if (pcxt->nworkers_launched > 0)
 			{
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index aab59d681c..e4698a28c4 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -708,6 +708,11 @@ typedef struct EState
 
 	bool		es_use_parallel_mode;	/* can we use parallel workers? */
 
+	int			es_parallel_workers_to_launch;	/* number of workers to
+												 * launch. */
+	int			es_parallel_workers_launched;	/* number of workers actually
+												 * launched. */
+
 	/* The per-query shared memory area to use for parallel execution. */
 	struct dsa_area *es_query_dsa;