Fixes for query_id feature

Ignore parallel workers in pg_stat_statements
  Oversight in 4f0b0966 which exposed queryid in parallel workers.
  Counters are aggregated by the main backend process so parallel workers
  would report duplicated activity, and could also report activity for the
  wrong entry as they are only aware of the top level queryid.

Fix thinko in pg_stat_get_activity when retrieving the queryid.

Remove unnecessary call to pgstat_report_queryid().

Reported-by: Amit Kapila, Andres Freund, Thomas Munro

Discussion: https://postgr.es/m/20210408051735.lfbdzun5zdlax5gd@alap3.anarazel.de p634GTSOqnDW86Owrn6qDAVosC5dJjXjp7BMfc5Gz1Q@mail.gmail.com

Author: Julien Rouhaud

contrib/pg_stat_statements/pg_stat_statements.c

@@ -47,6 +47,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include "access/parallel.h"
 #include "catalog/pg_authid.h"
 #include "common/hashfn.h"
 #include "executor/instrument.h"
@@ -278,8 +279,9 @@ static bool pgss_save;			/* whether to save stats across shutdown */
 
 
 #define pgss_enabled(level) \
+	(!IsParallelWorker() && \
 	(pgss_track == PGSS_TRACK_ALL || \
-	(pgss_track == PGSS_TRACK_TOP && (level) == 0))
+	(pgss_track == PGSS_TRACK_TOP && (level) == 0)))
 
 #define record_gc_qtexts() \
 	do { \

src/backend/executor/execParallel.c

@@ -1426,7 +1426,6 @@ ParallelQueryMain(dsm_segment *seg, shm_toc *toc)
 
 	/* Report workers' query and queryId for monitoring purposes */
 	pgstat_report_activity(STATE_RUNNING, debug_query_string);
-	pgstat_report_queryid(queryDesc->plannedstmt->queryId, false);
 
 	/* Attach to the dynamic shared memory area. */
 	area_space = shm_toc_lookup(toc, PARALLEL_KEY_DSA, false);

src/backend/utils/adt/pgstatfuncs.c

@@ -917,7 +917,7 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 			if (beentry->st_queryid == 0)
 				nulls[29] = true;
 			else
-				values[29] = DatumGetUInt64(beentry->st_queryid);
+				values[29] = UInt64GetDatum(beentry->st_queryid);
 		}
 		else
 		{