Show Parallel Bitmap Heap Scan worker stats in EXPLAIN ANALYZE

Nodes like Memoize report the cache stats for each parallel worker, so it
makes sense to show the exact and lossy pages in Parallel Bitmap Heap Scan
in a similar way.  Likewise, Sort shows the method and memory used for
each worker.

There was some discussion on whether the leader stats should include the
totals for each parallel worker or not.  I did some analysis on this to
see what other parallel node types do and it seems only Parallel Hash does
anything like this.  All the rest, per what's supported by
ExecParallelRetrieveInstrumentation() are consistent with each other.

Author: David Geier <[email protected]>
Author: Heikki Linnakangas <[email protected]>
Author: Donghang Lin <[email protected]>
Author: Alena Rybakina <[email protected]>
Author: David Rowley <[email protected]>
Reviewed-by: Dmitry Dolgov <[email protected]>
Reviewed-by: Michael Christofides <[email protected]>
Reviewed-by: Robert Haas <[email protected]>
Reviewed-by: Dilip Kumar <[email protected]>
Reviewed-by: Tomas Vondra <[email protected]>
Reviewed-by: Melanie Plageman <[email protected]>
Reviewed-by: Donghang Lin <[email protected]>
Reviewed-by: Masahiro Ikeda <[email protected]>
Discussion: https://postgr.es/m/b3d80961-c2e5-38cc-6a32-61886cdf766d%40gmail.com

1 files changed, 48 insertions, 10 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 6defd26df50..118db12903c 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -2010,8 +2010,7 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
-			if (es->analyze)
-				show_tidbitmap_info((BitmapHeapScanState *) planstate, es);
+			show_tidbitmap_info((BitmapHeapScanState *) planstate, es);
 			break;
 		case T_SampleScan:
 			show_tablesample(((SampleScan *) plan)->tablesample,
@@ -3628,31 +3627,70 @@ show_hashagg_info(AggState *aggstate, ExplainState *es)
 }
 
 /*
- * If it's EXPLAIN ANALYZE, show exact/lossy pages for a BitmapHeapScan node
+ * Show exact/lossy pages for a BitmapHeapScan node
  */
 static void
 show_tidbitmap_info(BitmapHeapScanState *planstate, ExplainState *es)
 {
+	if (!es->analyze)
+		return;
+
 	if (es->format != EXPLAIN_FORMAT_TEXT)
 	{
 		ExplainPropertyUInteger("Exact Heap Blocks", NULL,
-								planstate->exact_pages, es);
+								planstate->stats.exact_pages, es);
 		ExplainPropertyUInteger("Lossy Heap Blocks", NULL,
-								planstate->lossy_pages, es);
+								planstate->stats.lossy_pages, es);
 	}
 	else
 	{
-		if (planstate->exact_pages > 0 || planstate->lossy_pages > 0)
+		if (planstate->stats.exact_pages > 0 || planstate->stats.lossy_pages > 0)
 		{
 			ExplainIndentText(es);
 			appendStringInfoString(es->str, "Heap Blocks:");
-			if (planstate->exact_pages > 0)
-				appendStringInfo(es->str, " exact=" UINT64_FORMAT, planstate->exact_pages);
-			if (planstate->lossy_pages > 0)
-				appendStringInfo(es->str, " lossy=" UINT64_FORMAT, planstate->lossy_pages);
+			if (planstate->stats.exact_pages > 0)
+				appendStringInfo(es->str, " exact=" UINT64_FORMAT, planstate->stats.exact_pages);
+			if (planstate->stats.lossy_pages > 0)
+				appendStringInfo(es->str, " lossy=" UINT64_FORMAT, planstate->stats.lossy_pages);
 			appendStringInfoChar(es->str, '\n');
 		}
 	}
+
+	/* Display stats for each parallel worker */
+	if (planstate->pstate != NULL)
+	{
+		for (int n = 0; n < planstate->sinstrument->num_workers; n++)
+		{
+			BitmapHeapScanInstrumentation *si = &planstate->sinstrument->sinstrument[n];
+
+			if (si->exact_pages == 0 && si->lossy_pages == 0)
+				continue;
+
+			if (es->workers_state)
+				ExplainOpenWorker(n, es);
+
+			if (es->format == EXPLAIN_FORMAT_TEXT)
+			{
+				ExplainIndentText(es);
+				appendStringInfoString(es->str, "Heap Blocks:");
+				if (si->exact_pages > 0)
+					appendStringInfo(es->str, " exact=" UINT64_FORMAT, si->exact_pages);
+				if (si->lossy_pages > 0)
+					appendStringInfo(es->str, " lossy=" UINT64_FORMAT, si->lossy_pages);
+				appendStringInfoChar(es->str, '\n');
+			}
+			else
+			{
+				ExplainPropertyUInteger("Exact Heap Blocks", NULL,
+										si->exact_pages, es);
+				ExplainPropertyUInteger("Lossy Heap Blocks", NULL,
+										si->lossy_pages, es);
+			}
+
+			if (es->workers_state)
+				ExplainCloseWorker(n, es);
+		}
+	}
 }
 
 /*