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From: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
To: Richard Guo <guofenglinux@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: Clause accidentally pushed down ( Possible bug in Making Vars outer-join aware)
Date: Thu, 20 Apr 2023 10:06:51 +0500
Message-ID: <a83e8e21-ee4a-8b33-7ea5-8d0f754c8567@postgrespro.ru> (raw)
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	<efb33bee-145d-95a8-1048-2e7b8f282e2c@postgrespro.ru>
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	<CAMbWs49CB3txv_s3SwC1L2h1DiUPAn+v0-O4UFfg33b+HXNnTg@mail.gmail.com>

On 4/4/23 08:00, Richard Guo wrote:
> I found a thinko in the v1 patch: we need to consider syn_righthand
> rather than min_righthand of the pushed down outer joins as we want to
> know if the Var or PHV actually comes from within the syntactically
> nullable sides.  Attach v2 to fix this.
> 
> I have some concerns that the new added foreach loop is too expensive to
> be doing for each Var or PHV.  But maybe it's no problem since we only
> loop over pushed down joins here.
I have passed through your patch and the 
'postpone-adding-pushed-down-ojrelid-to-relids' patch step-by-step. It 
looks logically correct.
Honestly, I don't happy with the top patch, because it looks a bit 
peculiar, but the sqlancer long test (which detected the problem before) 
didn't show any problems here.
But one thought is bugging me: do we have a guarantee, what with these 
Identity 3 transformations and 'delaying up to completely performed' 
technique we don't lose some joininfo clauses?

-- 
Regards
Andrey Lepikhov
Postgres Professional






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  Subject: Re: Clause accidentally pushed down ( Possible bug in Making Vars outer-join aware)
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