From: Andres Freund <andres@anarazel.de>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: tableam: Perform CheckXidAlive check once per scan
Date: Thu, 29 Jan 2026 23:51:27 +0000
Message-ID: <E1vlbnK-0003nf-2n@gemulon.postgresql.org> (raw)
tableam: Perform CheckXidAlive check once per scan
Previously, the CheckXidAlive check was performed within the table_scan*next*
functions. This caused the check to be executed for every fetched tuple, an
unnecessary overhead.
To fix, move the check to table_beginscan* so it is performed once per scan
rather than once per row.
Note: table_tuple_fetch_row_version() does not use a scan descriptor;
therefore, the CheckXidAlive check is retained in that function. The overhead
is unlikely to be relevant for the existing callers.
Reported-by: Andres Freund <andres@anarazel.de>
Author: Dilip Kumar <dilipbalaut@gmail.com>
Suggested-by: Andres Freund <andres@anarazel.de>
Suggested-by: Amit Kapila <akapila@postgresql.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/tlpltqm5jjwj7mp66dtebwwhppe4ri36vdypux2zoczrc2i3mp%40dhv4v4nik...
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/87f7b824f20c1c06884ef0711b4d32dbf4461436
Modified Files
--------------
src/backend/access/heap/heapam.c | 10 -----
src/backend/access/index/genam.c | 30 +++++++-------
src/backend/access/table/tableam.c | 20 +++-------
src/include/access/tableam.h | 82 +++++++++++++++++---------------------
4 files changed, 57 insertions(+), 85 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: andres@anarazel.de, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: tableam: Perform CheckXidAlive check once per scan
In-Reply-To: <E1vlbnK-0003nf-2n@gemulon.postgresql.org>
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