Horton

Re: convert EXSITS to inner join gotcha and bug

David Rowley <david.rowley@2ndquadrant.com>

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From: David Rowley <david.rowley@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alexander Korotkov <a.korotkov@postgrespro.ru>, Teodor Sigaev <teodor@sigaev.ru>, Pgsql Hackers <pgsql-hackers@postgresql.org>
Date: 2017-04-30T00:14:27Z
Lists: pgsql-hackers 
On 29 April 2017 at 15:39, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I'm kind of strongly tempted to apply the second patch; but it would
> be fair to complain that reduce_unique_semijoins() is new development
> and should wait for v11.  Opinions?

My vote is for the non-minimal patch. Of course, I'd be voting for
minimal patch if this was for a minor version release fix, but we're
not even in beta yet for v10. The original patch was intended to fix
cases like this, although I'd failed to realise this particular case.


-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. Reduce semijoins with unique inner relations to plain inner joins.

  2. Fix mis-optimization of semijoins with more than one LHS relation.