From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix MVCC bug with prepared xact with subxacts on standby
Date: Thu, 27 Jun 2024 18:34:29 +0000
Message-ID: <E1sMtwy-003GMJ-IJ@gemulon.postgresql.org> (raw)
Fix MVCC bug with prepared xact with subxacts on standby
We did not recover the subtransaction IDs of prepared transactions
when starting a hot standby from a shutdown checkpoint. As a result,
such subtransactions were considered as aborted, rather than
in-progress. That would lead to hint bits being set incorrectly, and
the subtransactions suddenly becoming visible to old snapshots when
the prepared transaction was committed.
To fix, update pg_subtrans with prepared transactions's subxids when
starting hot standby from a shutdown checkpoint. The snapshots taken
from that state need to be marked as "suboverflowed", so that we also
check the pg_subtrans.
Backport to all supported versions.
Discussion: https://www.postgresql.org/message-id/6b852e98-2d49-4ca1-9e95-db419a2696e0@iki.fi
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/cbfbda78413a5b2f4807e029407dcc98a0e63162
Modified Files
--------------
src/backend/access/transam/twophase.c | 7 +++---
src/backend/access/transam/xlog.c | 14 ++++++-----
src/backend/storage/ipc/procarray.c | 18 +++++++++++---
src/backend/storage/ipc/standby.c | 6 ++---
src/include/storage/standby.h | 10 +++++++-
src/test/recovery/t/009_twophase.pl | 46 +++++++++++++++++++++++++++++++++++
src/tools/pgindent/typedefs.list | 1 +
7 files changed, 85 insertions(+), 17 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: heikki.linnakangas@iki.fi, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix MVCC bug with prepared xact with subxacts on standby
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