Re: Introduce XID age and inactive timeout based replication slot invalidation

On Wed, Feb 21, 2024 at 5:55 PM Bertrand Drouvot
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> > As far as the 0001 patch is concerned, it reports the
> > invalidation_reason as long as slot_contents.data.invalidated !=
> > RS_INVAL_NONE. I think this is okay.
> >
> > Thoughts?
>
> Yeah, looking at the code I agree that looks ok. OTOH, that looks confusing,
> maybe we should add a few words about it in the doc?

I'll think about it.

> Looking at v5-0001:
>
> + <entry role="catalog_table_entry"><para role="column_definition">
> + <structfield>invalidation_reason</structfield> <type>text</type>
> + </para>
> + <para>
>
> My initial thought was to put "conflict" value in this new field in case of
> conflict (not to mention the conflict reason in it). With the current proposal
> invalidation_reason could report the same as conflict_reason, which sounds weird
> to me.
>
> Does that make sense to you to use "conflict" as value in "invalidation_reason"
> when the slot has "conflict_reason" not NULL?

I'm thinking the other way around - how about we revert
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=007693f2a3ac2ac19affcb03ad43cdb36ccff5b5,
that is, put in place "conflict" as a boolean and introduce
invalidation_reason the text form. So, for logical slots, whenever the
"conflict" column is true, the reason is found in invaldiation_reason
column? How does it sound? Again the debate might be "conflict" vs
"invalidation", but that looks clean IMHO.

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com