Horton

Re: Large expressions in indexes can't be stored (non-TOASTable)

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Euler Taveira <euler@eulerto.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, "Jonathan S. Katz" <jkatz@postgresql.org>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-04-09T04:20:29Z
Lists: pgsql-hackers 
On Tue, Apr 08, 2025 at 11:21:31PM -0300, Euler Taveira wrote:
> The logical replication creates origin names as pg_SUBOID_RELID or pg_SUBOID.
> It means the maximum origin name is 24. This limited origin name also applies
> to pglogical that limits the name to 54 IIRC. I think that covers the majority
> of the logical replication setups. There might be a small number of custom
> logical replication systems that possibly use long names for replication
> origin. I've never seen a replication origin name longer than NAMEDATALEN.

pg_replication_origin_create() can be used with text as input for the
origin name, still your argument sounds sensible here as I would
suspect that most setups of logical replication are these.

> If you consider that the maximum number of replication origin is limited to 2
> bytes (65k distinct names), it is reasonable to restrict the replication
> origin names to 512 due to the high number of combinations. We generally
> expects that a catalog string uses "name" as type if it is an identifier; it
> could be the case for roname if author decided to be strict.

I would be more cautious than a limit on NAMEDATALEN.  The restriction
suggested by Nathan at 512 bytes should be plenty enough.

> This additional TOAST table has no or rare use. +1 for removing it. It is one
> less file, one less table and one less index; in short, one less source of data
> corruption. ;)

I guess that's the consensus, then.  No objections to the removal here.
--
Michael

Commits

  1. Ensure we have a snapshot when updating various system catalogs.

  2. Remove pg_replication_origin's TOAST table.

  3. Restrict password hash length.

  4. Ensure we have a snapshot when updating pg_index entries.

  5. Add TOAST table to pg_index.

  6. Add toast tables to most system catalogs