From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> |
Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Beena Emerson <memissemerson(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [HACKERS] path toward faster partition pruning |
Date: | 2018-02-26 18:27:58 |
Message-ID: | CA+TgmobZ9g5B4WSThBtjz3g_JsYPDLmpXAVaFbHjbs0yVq+n6Q@mail.gmail.com |
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On Sun, Feb 25, 2018 at 11:10 PM, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> I think I'm convinced that partopcintype OIDs can be used where I thought
> parttypid ones were necessary. The pruning patch uses the respective OID
> from this array when extracting the datum from an OpExpr to be compared
> with the partition bound datums. It's sensible, I now think, to require
> the extracted datum to be of partition opclass declared input type, rather
> than the type of the partition key involved. So, I removed the parttypid
> that I'd added to PartitionSchemeData.
>
> Updated the comments to make clear the distinction between and purpose of
> having both parttypcoll and partcollation. Also expanded the comment
> about partsupfunc a bit.
I don't think this fundamentally fixes the problem, although it does
narrow it. By requiring partcollation to match across every relation
with the same PartitionScheme, you're making partition-wise join fail
to work in some cases where it previously did. Construct a test case
where parttypcoll matches and partcollation doesn't; then, without the
patch, the two relations will have the same PartitionScheme and thus
be eligible for a partition-wise join, but with the patch, they will
have different PartitionSchemes and thus won't.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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