Feedback-ID: ia2694551:Fastmail
Date: Fri, 3 Apr 2026 21:31:48 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Antonin Houska <ah@cybertec.at>
Cc: Srinath Reddy Sadipiralla <srinath2133@gmail.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
 Mihail Nikalayeu <mihailnikalayeu@gmail.com>,
	Matthias van de Meent <boekewurm+postgres@gmail.com>,
 Pg Hackers <pgsql-hackers@lists.postgresql.org>,
	Robert Treat <rob@xzilla.net>
Subject: Re: Adding REPACK [concurrently]
Message-ID: <202604031922.t6lgu5a2alwo@alvherre.pgsql>
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On 2026-Apr-03, Alvaro Herrera wrote:

> - I polished the patch to reserve replication slots for REPACK.  Given
>   the new implementation of 0006 that was submitted implies that we can
>   now run multiple repacks concurrently, I changed the default of 1 to 5.

Srinath let me know that this new part was causing CI failures on
Windows.  This version v51 should be okay (or, at least, it passes for
me on CI).  Additional changes worth mentioning:

- I think it's nicer for the index_create() API to get a bit to indicate
  suppression of progress reporting; so existing callers don't need to
  do anything.  I guess this is mostly a matter of taste.

- I incorporated Srinath's fix for the PreventInTransactionBlock block.

- When CheckSlotRequirements() is to complain about
  "max_replication_slots or max_repack_replication_slots", it seems
  actually nicer to say exactly which one of these is the cause of the
  problem.  This is easy to change; patch 0010 does it; it requires
  passing down a "repack" flag all the way from
  CheckLogicalDecodingRequirements() and it needs to add an argument to
  CreateInitDecodingContext(), which is perhaps not so great.  On the
  whole I'm inclined to do it anyway, but I'm about equally happy to
  leave it alone.  This is what would change:

original:
        ereport(ERROR,
-               (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-                errmsg("replication slots can only be used if \"%s\" > 0 or \"%s\" > 0",
-                       "max_replication_slots", "max_repack_replication_slots")));

patched:
        ereport(ERROR,
+               errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+               errmsg("replication slots can only be used if \"%s\" > 0",
+                      repack ? "max_repack_replication_slots" : "max_replication_slots"));

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"This is a foot just waiting to be shot"                (Andrew Dunstan)

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