Re: Minimal logical decoding on standbys

Le mardi 27 juillet 2021, 09:23:48 CEST Drouvot, Bertrand a écrit :
> Thanks for the warning, rebase done and new v21 version attached.
>
> Bertrand

Hello,

I've taken a look at this patch, and it looks like you adressed every prior
remark, including the race condition Andres was worried about.

As for the basics: make check-world and make installcheck-world pass.

I think the beahviour when dropping a database on the primary should be
documented, and proper procedures for handling it correctly should be
suggested.

Something along the lines of:

"If a database is dropped on the primary server, the logical replication slot
on the standby will be dropped as well. This means that you should ensure that
the client usually connected to this slot has had the opportunity to stream
the latest changes before the database is dropped."

As for the patches themselves, I only have two small comments to make.

In patch 0002, in InvalidateConflictingLogicalReplicationSlots, I don't see the
need to check for an InvalidOid since we already check the SlotIsLogical:

+ /* We are only dealing with *logical* slot conflicts. */
+ if (!SlotIsLogical(s))
+ continue;
+
+ /* not our database and we don't want all the database,
skip */
+ if ((s->data.database != InvalidOid && s->data.database
!= dboid) && TransactionIdIsValid(xid))
+ continue;

In patch 0004, small typo in the test file:
+##################################################
+# Test standby promotion and logical decoding bheavior
+# after the standby gets promoted.
+##################################################

Thank you for working on this !

Regards,

--
Ronan Dunklau