Re: Conflict detection for update_deleted in logical replication

On Sat, Jan 18, 2025 at 9:15 AM Zhijie Hou (Fujitsu)
<houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
>
> Here is the V24 patch set. I modified 0004 patch to implement the slot
> Invalidation part. Since the automatic recovery could be an optimization and
> the discussion is in progress, I didn't implement that part.

Few comments for patch-0004
====
src/backend/replication/slot.c

1) Need to describe the new macro RS_INVAL_CONFLICT_RETENTION_DURATION
in the comments above InvalidateObsoleteReplicationSlots(), where all
other invalidation causes are explained.
...
* Whether a slot needs to be invalidated depends on the cause. A slot is
* removed if it:
* - RS_INVAL_WAL_REMOVED: requires a LSN older than the given segment
* - RS_INVAL_HORIZON: requires a snapshot <= the given horizon in the given
* db; dboid may be InvalidOid for shared relations
* - RS_INVAL_WAL_LEVEL: is logical
...

2) Can we mention the GUC parameter that defines this "maximum limit"
while reporting?

+
+ case RS_INVAL_CONFLICT_RETENTION_DURATION:
+ appendStringInfo(&err_detail, _("The duration for retaining conflict
information exceeds the maximum limit."));
+ break;
+

Something like -
"The duration for retaining conflict information exceeds the maximum
limit configured in \"%s\".","max_conflict_retention_duration"

=====
doc/src/sgml/ref/create_subscription.sgml

3)
+ <para>
+ Note that setting a non-zero value for this option could lead to
+ conflict information being removed prematurely, potentially missing
+ some conflict detections.
+ </para>

Should we add the above info as a “Warning” in the docs?