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commit    5702277ca97396384eaf5c58d582b79b9984ce73
Author:   Robert Haas <rhaas@postgresql.org>
Date:     Fri Apr 15 15:49:41 2016 +0000
First released in: 9.6.0

    Tweak EXPLAIN for parallel query to show workers launched.
    
    The previous display was sort of confusing, because it didn't
    distinguish between the number of workers that we planned to launch
    and the number that actually got launched.  This has already confused
    several people, so display both numbers and label them clearly.
    
    Julien Rouhaud, reviewed by me.


 src/backend/commands/explain.c    | 10 +++++++++-
 src/backend/executor/nodeGather.c |  1 +
 src/include/nodes/execnodes.h     |  1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 713cd0e3da8..379fc5c429e 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -1339,8 +1339,16 @@ ExplainNode(PlanState *planstate, List *ancestors,
 				if (plan->qual)
 					show_instrumentation_count("Rows Removed by Filter", 1,
 											   planstate, es);
-				ExplainPropertyInteger("Number of Workers",
+				ExplainPropertyInteger("Workers Planned",
 									   gather->num_workers, es);
+				if (es->analyze)
+				{
+					int			nworkers;
+
+					nworkers = ((GatherState *) planstate)->nworkers_launched;
+					ExplainPropertyInteger("Workers Launched",
+										   nworkers, es);
+				}
 				if (gather->single_copy)
 					ExplainPropertyText("Single Copy",
 									  gather->single_copy ? "true" : "false",
diff --git a/src/backend/executor/nodeGather.c b/src/backend/executor/nodeGather.c
index 3f0ed696327..3834ed678cb 100644
--- a/src/backend/executor/nodeGather.c
+++ b/src/backend/executor/nodeGather.c
@@ -166,6 +166,7 @@ ExecGather(GatherState *node)
 			 */
 			pcxt = node->pei->pcxt;
 			LaunchParallelWorkers(pcxt);
+			node->nworkers_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 dbec07e5a37..ee4e1896893 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1956,6 +1956,7 @@ typedef struct GatherState
 	struct ParallelExecutorInfo *pei;
 	int			nreaders;
 	int			nextreader;
+	int			nworkers_launched;
 	struct TupleQueueReader **reader;
 	TupleTableSlot *funnel_slot;
 	bool		need_to_scan_locally;


[parent: 6b85d4ba9b09]