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Re: [HACKERS] convert EXSITS to inner join gotcha and bug - Mailing list pgsql-hackers

From Tom Lane
Subject Re: [HACKERS] convert EXSITS to inner join gotcha and bug
Date
Msg-id 26008.1493389618@sss.pgh.pa.us
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In response to Re: [HACKERS] convert EXSITS to inner join gotcha and bug  (Alexander Korotkov <a.korotkov@postgrespro.ru>)
Responses Re: [HACKERS] convert EXSITS to inner join gotcha and bug  (Teodor Sigaev <teodor@sigaev.ru>)
Re: [HACKERS] convert EXSITS to inner join gotcha and bug  (David Rowley <david.rowley@2ndquadrant.com>)
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Alexander Korotkov <a.korotkov@postgrespro.ru> writes:
> I've reproduced this bug on d981074c.
> On default config, after loading example.sql.bz2 and VACUUM ANALYZE, query
> result is OK.
> But with seqscan and hashjoin disabled, query returns 0 rows.

Ah, thanks for the clue about enable_hashjoin, because it wasn't
reproducing for me as stated.

It looks like in the case that's giving wrong answers, the mergejoin
is wrongly getting marked as "Inner Unique".  Something's a bit too
cheesy about that planner logic --- not sure what, yet.
        regards, tom lane

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