Date: Thu, 7 Sep 2023 14:21:43 -0400
From: Bruce Momjian <bruce@momjian.us>
To: m.sakrejda@gmail.com, pgsql-docs@lists.postgresql.org
Subject: Re: pg_class.relpages documentation does not mention relpages corner
 case
Message-ID: <ZPoUt3hr57mdwkDR@momjian.us>
References: <168600622919.640.13784585346362749956@wrigleys.postgresql.org>
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On Mon, Jun  5, 2023 at 11:03:49PM +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
> 
> Page: https://www.postgresql.org/docs/14/catalog-pg-class.html
> Description:
> 
> In the pg_class documentation [1], the relpages column is described as
> 
> >Size of the on-disk representation of this table in pages (of size BLCKSZ).
> This is only an estimate used by the planner. It is updated by VACUUM,
> ANALYZE, and a few DDL commands such as CREATE INDEX.
> 
> However, it looks like this is -1 for partitioned tables. At least for ones
> that have children and have been analyze since adding a child partition, it
> seems. I'm not sure how to word that concisely, but should the documentation
> note this case? Or can this just be zero for partitioned tales? I'm not sure
> if it's too late for that, but they don't actually have any relpages, so it
> seems odd that they need a sentinel value.

Uh, there are discussions about needing to run ANALYZE on partitioned
tables, so in those cases the statistics would be cumulative of all
partitions:

	https://www.postgresql.org/message-id/20230112232747.GA2111950@nathanxps13

If we set the relpages to zero, that would not be reflecting the
partitions.  I feel -1 is probably the best unless we want to put the
total of all partitions in there, but that would be confusing too.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.