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Message-ID: <fc43dd15-564b-4239-bc78-d0cc47b114d7@postgrespro.ru>
Date: Tue, 18 Jun 2024 09:57:11 +0300
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Subject: Maybe don't process multi xmax in FreezeMultiXactId() if it is
 already marked as invalid?
From: "Anton A. Melnikov" <a.melnikov@postgrespro.ru>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <21ece835-b671-4656-9f35-008b9f355034@postgrespro.ru>
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On 14.06.2024 10:45, Anton A. Melnikov wrote:

> The src/backend/access/heap/README.tuplock says about HEAP_XMAX_INVALID bit
> that "Any tuple with this bit set does not have a valid value stored in XMAX."
> 
> Found that FreezeMultiXactId() tries to process such an invalid multi xmax
> and may looks for an update xid in the pg_multixact for it.
> 
> Maybe not do this work in FreezeMultiXactId() and exit immediately if the
> bit HEAP_XMAX_INVALID was already set?
> 

Seems it is important to save the check that multi xmax is not behind relminmxid.
So saved it and correct README.tuplock accordingly.

Would be glad if someone take a look at the patch attached.


With the best regards,

-- 
Anton A. Melnikov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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