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
------
REL_12_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/5dea6628b32d8092e789d9e31509ed74840a271e
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 | 48 ++++++++++++++++++++++++++++++++++-
src/tools/pgindent/typedefs.list | 1 +
7 files changed, 86 insertions(+), 18 deletions(-)