Re: Wrong results from Parallel Hash Full Join - Mailing list pgsql-hackers

On Wed, Jun 07, 2023 at 05:16:12PM -0400, Melanie Plageman wrote:
> On Fri, May 19, 2023 at 8:05 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Considering that this is a parallel plan, I don't think there's any
>> mystery about why an ORDER-BY-less query might have unstable output
>> order; the only mystery is why more of the buildfarm hasn't failed.
>> Can we just add "ORDER BY t1.id" to this query?  It looks like you
>> get the same PHJ plan, although now underneath Sort/Gather Merge.
>
> Yes, this was an oversight on my part. Attached is the patch that does
> just what you suggested.

Confirmed that adding an ORDER BY adds a Sort node between a Gather
Merge and a Parallel Hash Full Join, not removing coverage.

This has fallen through the cracks and conchuela has failed again
today, so I went ahead and applied the fix on HEAD.  Thanks!
--
Michael