From 5e2aae4b94ff79d87c1d58bfd6f21933a857b7ee Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Tue, 18 Aug 2026 13:09:00 -0400 Subject: [PATCH v16 16/21] Add VACUUM write combining test Though vacuum uses the same write write combining logic that is used by COPY FROM and regular backends needing a clean buffer, it is worth exercising it. --- .../modules/test_aio/t/005_write_combining.pl | 31 +++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/src/test/modules/test_aio/t/005_write_combining.pl b/src/test/modules/test_aio/t/005_write_combining.pl index 2ccf10cf2c0..7aa18bbdf96 100644 --- a/src/test/modules/test_aio/t/005_write_combining.pl +++ b/src/test/modules/test_aio/t/005_write_combining.pl @@ -30,6 +30,7 @@ test_checkpointer_combines_writes($node, $block_size); test_regular_backend_combines_writes($node, $block_size); test_eager_clean_combines_writes($node, $block_size); test_copy_from_combines_writes($node, $block_size); +test_vacuum_combines_writes($node, $block_size); $node->stop(); @@ -388,3 +389,33 @@ sub test_eager_clean_combines_writes $psql->quit(); } + +sub test_vacuum_combines_writes +{ + my ($node, $block_size) = @_; + + # ~120 blocks: enough to wrap vacuum's ring (sized below) several + # times, with dead tuples on every page so pruning dirties every page + # vacuum reads into the ring. + # + # This uses a regular (logged) table, so at least one test covers logged + # tables. We don't expect WAL flush timing to affect the results because the + # target buffer is always included in the batch and will do a combined write + # regardless of whether or not it has to flush WAL. + $node->safe_psql( + 'postgres', qq( + CREATE TABLE wc_vacuum (id int, payload text); + INSERT INTO wc_vacuum SELECT g, repeat('y', 200) FROM generate_series(1, 3600) AS g; + DELETE FROM wc_vacuum WHERE id % 5 = 0; + SELECT flush_rel_buffers('wc_vacuum'::regclass); + SELECT evict_rel('wc_vacuum'::regclass); + )); + + $node->safe_psql('postgres', "SELECT pg_stat_reset_shared('io')"); + $node->safe_psql('postgres', + "VACUUM (BUFFER_USAGE_LIMIT '256kB') wc_vacuum"); + $node->safe_psql('postgres', 'SELECT pg_stat_force_next_flush()'); + + assert_combined_writes($node, 'vacuum', 'client backend', 'vacuum', + $block_size); +} -- 2.47.3