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help / color / mirror / Atom feedFrom: Tatsuo Ishii <ishii@postgresql.org>
To: pgpool-committers@lists.postgresql.org
Subject: pgpool: Revert "Fix do_query to send sync rather than flush."
Date: Sun, 06 Sep 2026 22:56:42 +0000
Message-ID: <E1x3Lmz-00000000xmc-1j3v@gothos.postgresql.org> (raw)
Revert "Fix do_query to send sync rather than flush."
This reverts commit a6ac3ea54cc6c7d4b251f843154589a5d6dce31c.
This breaks implicit transaction behavior created by a pipeline.
-----------------------------------------------------------------
$ psql -p 11000 -a -f failure.sql test
DROP TABLE test;
DROP TABLE
-- start a pipeline
\startpipeline
-- CREATE a table
CREATE TABLE test(i int);
-- SELECT non-existent table, which raises an error,
-- and aborts the implicit transaction started by the pipeline.
SELECT * from a;
-- Recover from the error and closes the implicit transaction.
\syncpipeline
\endpipeline
CREATE TABLE
psql:failure.sql:11: ERROR: relation "a" does not exist
LINE 1: SELECT * from a;
^
-- Try to SELECT the table created in the previous pipeline.
-- This should fail because the creation of the table "test" was rollbacked.
SELECT * from test;
i
---
(0 rows)
-----------------------------------------------------------------
In this example, a table named "test" is created in a pipeline. Then
a SELECT is executed. Because the SELECT tries to retrieve rows from
non-existent table "a", it causes an error and a roll back of the
implicit transaction started by the pipeline. As a result, the table
"test" created in the pipeline does not exist at the end of the
pipeline. However, a "sync" message was issued by do_query() while
obtaining information regarding table "a". As the sync message caused
commit of the implicit transaction started by the pipeline, creation
of "test" was not roll backed by the subsequent erroneous SELECT.
IMO this is a serious data consistency issue because it breaks the
transaction semantics. If I directly connects to PostgreSQL or pgpool
by the previous commit, and run the script, it ends up with:
SELECT * from test;
psql:failure.sql:14: ERROR: relation "test" does not exist
LINE 1: SELECT * from test;
^
which is the expected behavior.
Discussion: https://www.postgresql.org/message-id/20260907.062521.1780975513572548706.ishii@postgresql.org
Backpatch-through: v4.3
Branch
------
V4_5_STABLE
Details
-------
https://git.postgresql.org/gitweb?p=pgpool2.git;a=commitdiff;h=987d806e6cd98a88a29489e6e10c2ebb93394...
Modified Files
--------------
src/protocol/pool_process_query.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
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To: pgpool-committers@postgresql.org
Cc: ishii@postgresql.org, pgpool-committers@lists.postgresql.org
Subject: Re: pgpool: Revert "Fix do_query to send sync rather than flush."
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