Fix buffer usage stats for nodes above Gather Merge.

Commit 85c9d347 addressed a similar problem for Gather and Gather
Merge nodes but forgot to account for nodes above parallel nodes.  This
still works for nodes above Gather node because we shut down the workers
for Gather node as soon as there are no more tuples.  We can do a similar
thing for Gather Merge as well but it seems better to account for stats
during nodes shutdown after completing the execution.

Reported-by: Stéphane Lorek, Jehan-Guillaume de Rorthais
Author: Jehan-Guillaume de Rorthais <jgdr@dalibo.com>
Reviewed-by: Amit Kapila
Backpatch-through: 10, where it was introduced
Discussion: https://postgr.es/m/20200718160206.584532a2@firost

diff --git a/src/backend/executor/execProcnode.c b/src/backend/executor/execProcnode.c
index 5662e7d74215e96f1cdd93e928f68afaa38c5744..01b7b926bf705dbaf0076c7bcdf2dfdc0022d1cb 100644 (file)
--- a/src/backend/executor/execProcnode.c
+++ b/src/backend/executor/execProcnode.c
@@ -755,8 +755,6 @@ ExecShutdownNode(PlanState *node)
 
    check_stack_depth();
 
-   planstate_tree_walker(node, ExecShutdownNode, NULL);
-
    /*
     * Treat the node as running while we shut it down, but only if it's run
     * at least once already.  We don't expect much CPU consumption during
@@ -770,6 +768,8 @@ ExecShutdownNode(PlanState *node)
    if (node->instrument && node->instrument->running)
        InstrStartNode(node->instrument);
 
+   planstate_tree_walker(node, ExecShutdownNode, NULL);
+
    switch (nodeTag(node))
    {
        case T_GatherState: