Horton

Re: BUG #14932: SELECT DISTINCT val FROM table gets stuck in an infinite loop

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, "Todd A. Cook" <tcook@blackducksoftware.com>, Thomas Munro <thomas.munro@enterprisedb.com>, PostgreSQL Bugs <pgsql-bugs@postgresql.org>
Date: 2018-01-29T18:11:38Z
Lists: pgsql-bugs 
Andres Freund <andres@anarazel.de> writes:
> On 2018-01-29 14:41:49 +0100, Tomas Vondra wrote:
>> Do you think repeating the performance testing is necessary? Not sure
>> when do you plan to push the changes, I may not have time for the tests
>> until after FOSDEM.

> Hm, it surely wouldn't hurt, but your previous result does give a lot of
> confidence - there's not a lot of fundamental difference leaving one
> more mitigation that should never reduce hashtable "quality" aside.  So
> I think going ahead with pushing and then benchmarking if possible, is
> reasonable?

Since the release wrap is this coming Monday, there's not really time to
wait and do something after FOSDEM ...

			regards, tom lane

Commits

  1. Improve bit perturbation in TupleHashTableHash.

  2. Prevent growth of simplehash tables when they're "too empty".

  3. Add stack-overflow guards in set-operation planning.