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: | 2023-01-24 14:31:24 |
Message-ID: | 9dfd49e6-6675-526e-0636-0ba09396744e@gmail.com |
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Lists: | pgsql-hackers |
Hi,
On 1/24/23 6:20 AM, Drouvot, Bertrand wrote:
> Hi,
>
> On 1/24/23 1:46 AM, Andres Freund wrote:
>> Hi,
>>
>> On 2023-01-19 10:43:27 +0100, Drouvot, Bertrand wrote:
>>> Sure, so with:
>>>
>>> 1) hot_standby_feedback set to off on the standby
>>> 2) create 2 logical replication slots on the standby and activate one
>>> 3) Invalidate the logical slots on the standby with VACUUM FULL on the primary
>>> 4) change hot_standby_feedback to on on the standby
>>>
>>> If:
>>>
>>> 5) pg_reload_conf() on the standby, then on the primary we get a catalog_xmin
>>> for the physical slot that the standby is attached to:
>>>
>>> postgres=# select slot_type,xmin,catalog_xmin from pg_replication_slots ;
>>> slot_type | xmin | catalog_xmin
>>> -----------+------+--------------
>>> physical | 822 | 748
>>> (1 row)
>>
>> How long did you wait for this to change?
>
> Almost instantaneous after pg_reload_conf() on the standby.
>
>> I don't think there's anything right
>> now that'd force a new hot-standby-feedback message to be sent to the primary,
>> after slots got invalidated.
>>
>> I suspect that if you terminated the walsender connection on the primary,
>> you'd not see it anymore either?
>>
>
> Still there after the standby is shutdown but disappears when the standby is re-started.
>
>> If that isn't it, something is broken in InvalidateObsolete...
>>
Yeah, you are right: ReplicationSlotsComputeRequiredXmin() is missing for the
logical slot invalidation case (and ReplicationSlotsComputeRequiredXmin() also
needs to take care of it).
I'll provide a fix in the next revision along with the TAP tests comments addressed.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
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