Re: Move wal_buffers_full to WalUsage (and report it in pgss/explain)

From: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
To: Ilia Evdokimov <ilya(dot)evdokimov(at)tantorlabs(dot)com>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Move wal_buffers_full to WalUsage (and report it in pgss/explain)
Date: 2025-02-11 14:05:18
Message-ID: Z6tZHszzUPx0MDB2@ip-10-97-1-34.eu-west-3.compute.internal
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Hi,

On Tue, Feb 11, 2025 at 03:30:09PM +0300, Ilia Evdokimov wrote:
> Hi,
>
> Thank you for your work!

Thanks for the review!

> 1. Perhaps In EXPLAIN you forget to check that usage->wal_buffers_full > 0:
>
> if ((usage->wal_records > 0) || (usage->wal_fpi > 0) || (usage->wal_bytes >
> 0))

I don't think that's possible to have wal_buffers_full > 0 if the above returns
false. A check is done at appendStringInfo() time so I think that's ok as it is.

> 2. I have a small suggestion for pg_stat_statements: would it make sense to
> move wal_buffers_full next to wal_records, wal_fpi and wal_bytes? This way,
> all WAL-related information would be grouped together.

I think I prefer to add it in "append" order. That way, that does not break
queries that rely on ordinal numbers.

Regards,

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

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