Widen lossy and exact page counters for Bitmap Heap Scan

david-rowley · david-rowley · commit 7340d9362a79 · 2024-07-08T14:43:09.000+12:00
Both of these counters were using the "long" data type. On MSVC that's a 32-bit type. On modern hardware, I was able to demonstrate that we can wrap those counters with a query that only takes 15 minutes to run. This issue may manifest itself either by not showing the values of the counters because they've wrapped and are less than zero, resulting in them being filtered by the > 0 checks in show_tidbitmap_info(), or bogus numbers being displayed which are modulus 2^32 of the actual number. Widen these counters to uint64. Discussion: https://postgr.es/m/CAApHDvpS_97TU+jWPc=T83WPp7vJa1dTw3mojEtAVEZOWh9bjQ@mail.gmail.com
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
@@ -3635,10 +3635,10 @@ show_tidbitmap_info(BitmapHeapScanState *planstate, ExplainState *es)
 {
 	if (es->format != EXPLAIN_FORMAT_TEXT)
 	{
-		ExplainPropertyInteger("Exact Heap Blocks", NULL,
-							   planstate->exact_pages, es);
-		ExplainPropertyInteger("Lossy Heap Blocks", NULL,
-							   planstate->lossy_pages, es);
+		ExplainPropertyUInteger("Exact Heap Blocks", NULL,
+								planstate->exact_pages, es);
+		ExplainPropertyUInteger("Lossy Heap Blocks", NULL,
+								planstate->lossy_pages, es);
 	}
 	else
 	{
@@ -3647,9 +3647,9 @@ show_tidbitmap_info(BitmapHeapScanState *planstate, ExplainState *es)
 			ExplainIndentText(es);
 			appendStringInfoString(es->str, "Heap Blocks:");
 			if (planstate->exact_pages > 0)
-				appendStringInfo(es->str, " exact=%ld", planstate->exact_pages);
+				appendStringInfo(es->str, " exact=" UINT64_FORMAT, planstate->exact_pages);
 			if (planstate->lossy_pages > 0)
-				appendStringInfo(es->str, " lossy=%ld", planstate->lossy_pages);
+				appendStringInfo(es->str, " lossy=" UINT64_FORMAT, planstate->lossy_pages);
 			appendStringInfoChar(es->str, '\n');
 		}
 	}
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
@@ -1817,8 +1817,8 @@ typedef struct BitmapHeapScanState
 	TBMIterator *tbmiterator;
 	TBMIterateResult *tbmres;
 	Buffer		pvmbuffer;
-	long		exact_pages;
-	long		lossy_pages;
+	uint64		exact_pages;
+	uint64		lossy_pages;
 	TBMIterator *prefetch_iterator;
 	int			prefetch_pages;
 	int			prefetch_target;

Original file line number	Diff line number	Diff line change
`@@ -3635,10 +3635,10 @@ show_tidbitmap_info(BitmapHeapScanState planstate, ExplainState es)`
`3635`	`3635`	`{`
`3636`	`3636`	`if (es->format != EXPLAIN_FORMAT_TEXT)`
`3637`	`3637`	`{`
`3638`		`- ExplainPropertyInteger("Exact Heap Blocks", NULL,`
`3639`		`- planstate->exact_pages, es);`
`3640`		`- ExplainPropertyInteger("Lossy Heap Blocks", NULL,`
`3641`		`- planstate->lossy_pages, es);`
	`3638`	`+ ExplainPropertyUInteger("Exact Heap Blocks", NULL,`
	`3639`	`+ planstate->exact_pages, es);`
	`3640`	`+ ExplainPropertyUInteger("Lossy Heap Blocks", NULL,`
	`3641`	`+ planstate->lossy_pages, es);`
`3642`	`3642`	`}`
`3643`	`3643`	`else`
`3644`	`3644`	`{`
`@@ -3647,9 +3647,9 @@ show_tidbitmap_info(BitmapHeapScanState planstate, ExplainState es)`
`3647`	`3647`	`ExplainIndentText(es);`
`3648`	`3648`	`appendStringInfoString(es->str, "Heap Blocks:");`
`3649`	`3649`	`if (planstate->exact_pages > 0)`
`3650`		`- appendStringInfo(es->str, " exact=%ld", planstate->exact_pages);`
	`3650`	`+ appendStringInfo(es->str, " exact=" UINT64_FORMAT, planstate->exact_pages);`
`3651`	`3651`	`if (planstate->lossy_pages > 0)`
`3652`		`- appendStringInfo(es->str, " lossy=%ld", planstate->lossy_pages);`
	`3652`	`+ appendStringInfo(es->str, " lossy=" UINT64_FORMAT, planstate->lossy_pages);`
`3653`	`3653`	`appendStringInfoChar(es->str, '\n');`
`3654`	`3654`	`}`
`3655`	`3655`	`}`