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Fix EXPLAIN Bitmap heap scan to count pages with no visible tuples

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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
This commit is contained in:
Heikki Linnakangas 2024-03-18 14:03:58 +02:00
parent 48018f1d8c
commit 0960ae1967
2 changed files with 8 additions and 6 deletions
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10
src/backend/executor/nodeBitmapHeapscan.c
View File

@ -204,6 +204,11 @@ 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,
@ -235,11 +240,6 @@ BitmapHeapNext(BitmapHeapScanState *node)
continue;
}
if (tbmres->ntuples >= 0)
node->exact_pages++;
else
node->lossy_pages++;
/* Adjust the prefetch target */
BitmapAdjustPrefetchTarget(node);
}

4
src/test/regress/expected/partition_prune.out
View File

@ -2848,6 +2848,7 @@ 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)
@ -2863,9 +2864,10 @@ 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