Skip site navigation (1) Skip section navigation (2)

pgsql: Temporarily (I hope) disable flattening of IN/EXISTS sublinks

From: tgl(at)postgresql(dot)org (Tom Lane)
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql: Temporarily (I hope) disable flattening of IN/EXISTS sublinks
Date: 2009-02-27 23:30:29
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-committerspgsql-hackers
Log Message:
Temporarily (I hope) disable flattening of IN/EXISTS sublinks that are within
the ON clause of an outer join.  Doing so is semantically correct but results
in de-optimizing queries that were structured to take advantage of the sublink
style of execution, as seen in recent complaint from Kevin Grittner.  Since
the user can get the other behavior by reorganizing his query, having the
flattening happen automatically is just a convenience, and that doesn't
justify breaking existing applications.  Eventually it would be nice to
re-enable this, but that seems to require a significantly different approach
to outer joins in the executor.

Modified Files:
        prepjointree.c (r1.63 -> r1.64)


pgsql-hackers by date

Next:From: Hannu KrosingDate: 2009-02-27 23:37:51
Subject: Re: xpath processing brain dead
Previous:From: Jeff DavisDate: 2009-02-27 23:01:14
Subject: Re: Index correlation versus multi-column indexes

pgsql-committers by date

Next:From: Tom LaneDate: 2009-02-28 00:10:52
Subject: pgsql: Reduce the maximum value of vacuum_cost_delay and
Previous:From: Tom LaneDate: 2009-02-27 22:41:38
Subject: pgsql: Tighten up join ordering rules to account for recent more-careful

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group