| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
| Cc: | Marko Tiikkaja <marko(at)joh(dot)to>, Andres Freund <andres(at)anarazel(dot)de>, andy(at)prestigedigital(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: BUG #15324: Non-deterministic behaviour from parallelised sub-query |
| Date: | 2018-08-13 18:04:47 |
| Message-ID: | 22819.1534183487@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> 2018-08-13 19:26 GMT+02:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> Likely, we need to treat the presence of a LIMIT/OFFSET in a sub-select
>> as making it parallel-unsafe, for exactly the reason that that makes
>> its results non-deterministic.
> Isn't it default behave of LIMIT/OFFSET without ORDER BY clause?
In principle, the planner could prove in some cases that the results
were deterministic even with LIMIT/OFFSET. BuT I doubt it's worth
the trouble. I certainly wouldn't advocate for such logic to be
part of a back-patched bug fix.
regards, tom lane
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