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: 2018-01-29T18:29:40Z
Lists: pgsql-bugs 
Andres Freund <andres@anarazel.de> writes:
> On January 29, 2018 10:11:38 AM PST, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Since the release wrap is this coming Monday, there's not really time
>> to wait and do something after FOSDEM ...

> I'm not sure what you're arguing for? I have measured the performance impacts, and am happy. That's why I do not want to wait till then.  Doing additional benchmarks after commit can't hurt tho...

I'm arguing for not waiting.  If Tomas does some more benchmarking and
finds something else we can improve, that's fine, but the stop-growing
patch is already an important fix compared to 10.1.

			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.