Horton

Re: Pgstattuple on Sequences: Seeking Community Feedback on Potential Patch

Nathan Bossart <nathandbossart@gmail.com>

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From: Nathan Bossart <nathandbossart@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Ayush Vatsa <ayushvatsa1810@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, michael@paquier.xyz
Date: 2024-08-26T18:14:28Z
Lists: pgsql-hackers 
On Mon, Aug 26, 2024 at 01:35:52PM -0400, Robert Haas wrote:
> On Mon, Aug 26, 2024 at 1:26 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
>> While it is apparently pretty uncommon to use pgstattuple on sequences,
>> this is arguably a bug that should be fixed and back-patched.
> 
> I don't understand what would make it a bug.
> 
>> IMHO it would be good to establish some level of consistency here.
> 
> Sure, consistency is good, all other things being equal, but just
> saying "well this used to work one way and now it works another way"
> isn't enough to say that there is a bug, or that something should be
> changed.

The reason I think it's arguably a bug is because it used to work fine and
then started ERROR-ing after commit 4b82664.  I'm fine with saying that we
don't think it's useful and intentionally deprecating it, but AFAICT no
such determination has been made.  I see no discussion about this on the
thread for commit 4b82664, and the only caller of pgstat_heap()
intentionally calls into the affected function for sequences (and has since
pgstattuple was introduced 18 years ago):

	if (RELKIND_HAS_TABLE_AM(rel->rd_rel->relkind) ||
		rel->rd_rel->relkind == RELKIND_SEQUENCE)
	{
		return pgstat_heap(rel, fcinfo);
	}

-- 
nathan

Commits

  1. Fix contrib/pageinspect's test for sequences.

  2. Reintroduce support for sequences in pgstattuple and pageinspect.

  3. Only allow heap in a number of contrib modules.