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From: Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: pryzby@telsasoft.com, sanyo.moura@tatic.net, Jeff Janes <jeff.janes@gmail.com>
Cc: david.rowley@2ndquadrant.com, Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Query with high planning time at version 11.1 compared versions 10.5 and 11.0
Date: Wed, 16 Jan 2019 14:52:15 +0900
Message-ID: <5C3EC68F.8030202@lab.ntt.co.jp> (raw)
In-Reply-To: <CAExHW5tTrOm92CRKwF7NY19HCA9tp=QrBxEq73HS6LzUHENh4g@mail.gmail.com>
References: <8db4eca8-6e76-70ff-f934-e0228a1cc298@lab.ntt.co.jp>
	<20181206075726.pig32e6thltb56hr@alvherre.pgsql>
	<CAExHW5umxU5FOoT8FBcqp-GWKMtZhnuEy7U6bNH8QfzvYwUgEQ@mail.gmail.com>
	<CAExHW5uFwP_1N7RV6s8piQBvygGH+rppS60nFNHB9DKEM04ShA@mail.gmail.com>
	<5C34846E.9090600@lab.ntt.co.jp>
	<96720c99-ffa0-01ad-c594-0504c8eda708@lab.ntt.co.jp>
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	<7354b5bf-5932-4c0c-81ee-d9550de18995@lab.ntt.co.jp>
	<5C36E105.2020902@lab.ntt.co.jp>
	<dd1de042-dca5-cfb9-bc66-2e39020fbf6a@lab.ntt.co.jp>
	<5C38910B.8010901@lab.ntt.co.jp>
	<a5c087d0-9ecc-1315-24d2-6303d14a6116@lab.ntt.co.jp>
	<CAExHW5tTrOm92CRKwF7NY19HCA9tp=QrBxEq73HS6LzUHENh4g@mail.gmail.com>

Hi Ashutosh,

(2019/01/15 13:29), Ashutosh Bapat wrote:
> I think, there's something better possible. Two partitioned relations
> won't use partition-wise join, if their partition schemes do not match.
> Partitioned relations with same partitioning scheme share
> PartitionScheme pointer. PartitionScheme structure should get an extra
> counter, maintaining a count of number of partitioned relations sharing
> that structure. When this counter is 1, that relation is certainly not
> going to participate in PWJ and thus need not have all the structure
> required by PWJ set up. If we use this counter coupled with
> enable_partitionwise_join flag, we can get rid of
> consider_partitionwise_join flag altogether, I think.

Interesting!

That flag was introduced to disable PWJs when whole-row Vars are 
involved, as you know, so I think we need to first eliminate that 
limitation, to remove that flag.

Thanks!

Best regards,
Etsuro Fujita





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