From d3d95f5839952d5bfa089a318a9d11809eb48ac2 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 18 Mar 2024 14:04:17 +0200
Subject: [PATCH] Fix EXPLAIN Bitmap heap scan to count pages with no visible
tuples
Previously, bitmap heap scans only counted lossy and exact pages for
explain when there was at least one visible tuple on the page.
heapam_scan_bitmap_next_block() returned true only if there was a
"valid" page with tuples to be processed. However, the lossy and exact
page counters in EXPLAIN should count the number of pages represented
in a lossy or non-lossy way in the constructed bitmap, regardless of
whether or not the pages ultimately contained visible tuples.
Backpatch to all supported versions.
Author: Melanie Plageman
Discussion: https://www.postgresql.org/message-id/CAAKRu_ZwCwWFeL_H3ia26bP2e7HiKLWt0ZmGXPVwPO6uXq0vaA@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAAKRu_bxrXeZ2rCnY8LyeC2Ls88KpjWrQ%2BopUrXDRXdcfwFZGA@mail.gmail.com
---
src/backend/executor/nodeBitmapHeapscan.c | 10 +++++-----
src/test/regress/expected/partition_prune.out | 4 +++-
2 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c
index f6fe07ad703..f0ac4e27d95 100644
--- a/src/backend/executor/nodeBitmapHeapscan.c
+++ b/src/backend/executor/nodeBitmapHeapscan.c
@@ -207,6 +207,11 @@ BitmapHeapNext(BitmapHeapScanState *node)
BitmapAdjustPrefetchIterator(node, tbmres);
+ if (tbmres->ntuples >= 0)
+ node->exact_pages++;
+ else
+ node->lossy_pages++;
+
/*
* We can skip fetching the heap page if we don't need any fields
* from the heap, and the bitmap entries don't need rechecking,
@@ -238,11 +243,6 @@ BitmapHeapNext(BitmapHeapScanState *node)
continue;
}
- if (tbmres->ntuples >= 0)
- node->exact_pages++;
- else
- node->lossy_pages++;
-
/* Adjust the prefetch target */
BitmapAdjustPrefetchTarget(node);
}
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 5f3610369a1..fa1f2f230eb 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -2812,6 +2812,7 @@ update ab_a1 set b = 3 from ab where ab.a = 1 and ab.a = ab_a1.a;
Index Cond: (a = 1)
-> Bitmap Heap Scan on ab_a1_b3 ab_a1_3 (actual rows=0 loops=1)
Recheck Cond: (a = 1)
+ Heap Blocks: exact=1
-> Bitmap Index Scan on ab_a1_b3_a_idx (actual rows=1 loops=1)
Index Cond: (a = 1)
-> Materialize (actual rows=1 loops=1)
@@ -2827,9 +2828,10 @@ update ab_a1 set b = 3 from ab where ab.a = 1 and ab.a = ab_a1.a;
Index Cond: (a = 1)
-> Bitmap Heap Scan on ab_a1_b3 ab_3 (actual rows=0 loops=1)
Recheck Cond: (a = 1)
+ Heap Blocks: exact=1
-> Bitmap Index Scan on ab_a1_b3_a_idx (actual rows=1 loops=1)
Index Cond: (a = 1)
-(34 rows)
+(36 rows)
table ab;
a | b