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From: Tom Lane <[email protected]>
To: Geoff Winkless <[email protected]>
Cc: pgsql-generallists.postgresql.org <[email protected]>
Subject: Re: UNLOGGED table CREATEd on one connection not immediately visible to another connection
Date: Thu, 29 Jan 2026 10:41:27 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAEzk6ff5yHiJWDCoLcmqwC36O=VqLEHjbU2pcpYpOvdScM3t5g@mail.gmail.com>
References: <CAEzk6ff5yHiJWDCoLcmqwC36O=VqLEHjbU2pcpYpOvdScM3t5g@mail.gmail.com>

Geoff Winkless <[email protected]> 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

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