From: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> |
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To: | noah(at)leadboat(dot)com |
Cc: | tgl(at)sss(dot)pgh(dot)pa(dot)us, peter_e(at)gmx(dot)net, robertmhaas(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: UNION ALL on partitioned tables won't use indices. |
Date: | 2014-02-28 05:45:51 |
Message-ID: | 20140228.144551.215885523.horiguchi.kyotaro@lab.ntt.co.jp |
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Thread: | |
Lists: | pgsql-hackers |
Sorry, I did wrong test.
> > > Noah Misch <noah(at)leadboat(dot)com> writes:
> > > > If the attached patch version looks reasonable, I will commit it.
> > >
> > > The test case is completely bogus, as the query explained is significantly
> > > different from the query executed. I'm not sure whether you can just
> > > remove the extra ORDER BY column without getting machine-dependent
> > > results, though.
> >
> > Each query tests something slightly different. The EXPLAIN verifies that we
> > can MergeAppend given this query structure, and the plain SELECT verifies that
> > any join tree contortions we made to achieve that do not change the answer.
>
> I think Tom said that the second query can yield the same result
> even if the 2nd column in orderby is removed so the pertinence of
> it seems doubtful. Actually the altered query gave me the same
> result on my workset (CentOS6.5/x86-64).
No, no! It was actually returned a *different* result. I
accidentially(?) added 'desc' to the '2'. Please forget it.
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
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