From: | "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, fabriziomello(at)gmail(dot)com, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, Rahila Syed <rahila(dot)syed(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Minimal logical decoding on standbys |
Date: | 2023-01-16 14:28:54 |
Message-ID: | 450e018e-d0e7-bcc3-ef8e-ab7c3f1b6dd7@gmail.com |
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Lists: | pgsql-hackers |
Hi,
On 1/13/23 10:17 AM, Drouvot, Bertrand wrote:
> Hi,
>
> On 1/11/23 9:27 PM, Andres Freund wrote:
>> Hi,
>>
>> On 2023-01-06 10:52:06 +0100, Drouvot, Bertrand wrote:
>>
>> The problem I have with that is that I saw a lot of flakiness in the tests due
>> to the race condition. So introducing them in that order just doesn't make a
>> whole lot of sense to me.
>
> You are right it does not make sense to introduce fixing the race condition after the TAP tests
> and after introducing the decoding logic. I'll reorder the sub-patches.
>
V40 attached is changing the sub-patches ordering.
>> The suggested path in earlier versions to avoid doing so was to make sure that
>> we pass down the Relation for the table into the necessary functions. Did you
>> explore that any further?
>
> So, for gistXLogPageReuse() and _bt_delitems_delete() this is "easy" to pass the Heap Relation.
> This is what was done in earlier versions of this patch series.
>
> But we would need to define a way to propagate the Heap Relation for those 2 functions:
>
> _bt_log_reuse_page()
> vacuumRedirectAndPlaceholder()
>
V40 is getting rid of the new indisusercatalog field in pg_index and is passing the
heap relation all the way down to _bt_log_reuse_page() and vacuumRedirectAndPlaceholder() instead
(and obviously to gistXLogPageReuse() and _bt_delitems_delete() too).
Remarks:
1) V40 adds the heap relation in the IndexVacuumInfo and ParallelVacuumState structs. It is used
for the _bt_log_reuse_page() and vacuumRedirectAndPlaceholder() cases where I did not find any place
where to get the heap relation from in the existing code path.
2) V40 adds a "real" heap relation to all the _bt_getbuf() calls. Another option could have been
to add it only for the code paths leading to _bt_log_reuse_page() but I thought it is cleaner to
do it for all of them.
> I will give it another look, also because I just realized that it could be beneficial
> for vacuumRedirectAndPlaceholder() too, as per this comment:
>
> "
> /* XXX: providing heap relation would allow more pruning */
> vistest = GlobalVisTestFor(NULL);
> "
Now, we could also pass the heap relation to GlobalVisTestFor() in vacuumRedirectAndPlaceholder().
Could be done in or independently of this patch series once committed (it's not part of V40).
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
Attachment | Content-Type | Size |
---|---|---|
v40-0006-Doc-changes-describing-details-about-logical-dec.patch | text/plain | 2.1 KB |
v40-0005-New-TAP-test-for-logical-decoding-on-standby.patch | text/plain | 20.4 KB |
v40-0004-Fixing-Walsender-corner-case-with-logical-decodi.patch | text/plain | 7.5 KB |
v40-0003-Allow-logical-decoding-on-standby.patch | text/plain | 10.8 KB |
v40-0002-Handle-logical-slot-conflicts-on-standby.patch | text/plain | 32.4 KB |
v40-0001-Add-info-in-WAL-records-in-preparation-for-logic.patch | text/plain | 72.1 KB |
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