Re: UNLOGGED table CREATEd on one connection not immediately visible to another connection

On 1/29/26 07:04, Geoff Winkless wrote:
> Hi
>
> 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.
>
> If we were somehow failing to create the table then the retries would
> never work, and we absolutely don't send the qreftmp ID to the second
> process until we've successfully INSERTed all of the records, so the
> race isn't on the application side. There's no explicit transactions
> in either process involved, they all just use implicit autocommit, so
> I don't see that this can be a DDL versioning issue.
>
> I'm loathe to point the finger at PG because I'm sure that if this
> were a real issue it would have been flagged up well before now, but
> I've been staring at our code for days and I'm stumped. Any
> suggestions?

Provide the code for the procedure(s) that create the table and send the
ID to the other process.

Question, why is this not run in a single process?

>
> Thanks
>
> Geoff
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com