Horton

Re: Small memory fixes for pg_createsubcriber

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Euler Taveira <euler@eulerto.com>, "ranier.vf@gmail.com" <ranier.vf@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2025-02-12T23:56:53Z
Lists: pgsql-hackers

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On Wed, Feb 12, 2025 at 12:00:03PM -0500, Andres Freund wrote:
> Particularly for something like libpq it's not quitetrivial to add
> attributes like this, of course. We can't even depend on pg_config.h.
> 
> One way would be to define them in libpq-fe.h, guarded by an #ifdef, that's
> "armed" by a commandline -D flag, if the compiler is supported?

Interesting set of tricks.

I have looked at bit at the uses of PQescapeLiteral() and
PQescapeIdentifier() in the tree.  On top of the one in pg_amcheck you
are just pointing to, there is an inconsistency in pg_upgrade.c for
set_locale_and_encoding() where datlocale_literal may be allocated
with a pg_strdup() or a PQescapeLiteral() depending on the path.  The
code has been using PQfreemem() for the pg_strdup() allocation, which
is logically incorrect.

The pg_upgrade path is fancy as designed this way, for sure, but
that's less invasive than hardcoding three times "NULL".  Any thoughts
about backpatching something like that for both of them?
--
Michael

Commits

  1. pg_upgrade: Fix inconsistency in memory freeing

  2. pg_amcheck: Fix inconsistency in memory freeing

  3. Fix some inconsistencies with memory freeing in pg_createsubscriber

  4. Drop pre-existing subscriptions from the converted subscriber.