From: Tom Lane <tgl@sss.pgh.pa.us>
To: Geoff Winkless <pg@ukku.uk>
cc: "pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
Subject: Re: UNLOGGED table CREATEd on one connection not immediately visible to another connection
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Comments: In-reply-to Geoff Winkless <pg@ukku.uk>
	message dated "Thu, 29 Jan 2026 15:04:43 +0000"
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Date: Thu, 29 Jan 2026 10:41:27 -0500
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Geoff Winkless <pg@ukku.uk> writes:
> In our application we have a situation where once a day one process
> CREATEs an UNLOGGED table and INSERTs several hundred records using
> individual queries (no explicit transactions) all of which return
> successfully. We then send the ID of the table that we have created
> over a TCP socket to a second process, which runs a query that JOINs
> against that new table.

> Unfortunately quite often the second process is getting a
> PGRES_FATAL_ERROR with

> Primary: relation "qreftmp750" does not exist

> Now (and this is very important) this appears to be a race condition,
> because when that process immediately retries the same query (which we
> do when we get FATAL_ERROR) it sometimes works on the second or third
> (or even 11th) attempt.

Perhaps the second process is querying a standby server rather than
the primary?  Replication lag could explain this.  I don't really
believe that it's possible within a single PG server, though.
We take very substantial pains to avoid the race condition you're
positing.

If there is anything in your client software stack capable of issuing
implicit begin/commit, that'd deserve a second/third/fourth look...

			regards, tom lane