Re: Buffer locking is special (hints, checksums, AIO writes)

From: Antonin Houska <ah(at)cybertec(dot)at>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Kirill Reshke <reshkekirill(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Subject: Re: Buffer locking is special (hints, checksums, AIO writes)
Date: 2026-03-13 15:01:40
Message-ID: 38845.1773414100@localhost
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Andres Freund <andres(at)anarazel(dot)de> wrote:

> Probably need to update the comments a bit. What about something like
>
>
> /*
> * Is the snapshot implemented as an MVCC snapshot (i.e. it uses
> * SNAPSHOT_MVCC). If so, there will be at most be one visible row in a chain
> * of updated tuples, and each visible tuple will be seen exactly once.
> */
> #define IsMVCCSnapshot(snapshot) \

The ", and each visible tuple ..." part seemed to me redundant, so I omitted
it. If you think I'm wrong, please add it yourself when committing the patch.

I also added a comment to the IsHistoricMVCCSnapshot(), trying to explain what
"historic" means.

--
Antonin Houska
Web: https://www.cybertec-postgresql.com

Attachment Content-Type Size
v2-Refine-checking-of-snapshot-type.patch text/x-diff 3.9 KB

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