Don't set ThisTimeLineID when there's no reason to do so.
authorRobert Haas <rhaas@postgresql.org>
Fri, 5 Nov 2021 16:43:04 +0000 (12:43 -0400)
committerRobert Haas <rhaas@postgresql.org>
Fri, 5 Nov 2021 16:43:04 +0000 (12:43 -0400)
commitcaf1f675b88d1aa67ea3fb642e8f38b470cc911e
treefda9433cd4ab26c088a50ba31e83747f9620adb0
parentd74b54b3ddf710926a44bf3f9c87c00e6f82d825
Don't set ThisTimeLineID when there's no reason to do so.

In slotfuncs.c, pg_replication_slot_advance() needs to determine
the LSN up to which the slot should be advanced, but that doesn't
require us to update ThisTimeLineID, because none of the code called
from here depends on it. If the replication slot is logical,
pg_logical_replication_slot_advance will call read_local_xlog_page,
which does use ThisTimeLineID, but also takes care of making sure
it's up to date. If the replication slot is physical, the timeline
isn't used for anything at all.

In logicalfuncs.c, pg_logical_slot_get_changes_guts() has the same
issue: the only code we're going to run that cares about timelines
is in or downstream of read_local_xlog_page, which already makes
sure that the correct value gets set. Hence, don't do it here.

Patch by me, reviewed and tested by Michael Paquier, Amul Sul, and
Álvaro Herrera.

Discussion: https://postgr.es/m/CA+TgmobfAAqhfWa1kaFBBFvX+5CjM=7TE=n4r4Q1o2bjbGYBpA@mail.gmail.com
src/backend/replication/logical/logicalfuncs.c
src/backend/replication/slotfuncs.c