| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Jeff Davis <pgsql(at)j-davis(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Default setting for enable_hashagg_disk |
| Date: | 2020-07-27 19:52:32 |
| Message-ID: | 20200727195232.GA22546@alvherre.pgsql |
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| Lists: | pgsql-docs pgsql-hackers |
On 2020-Jul-27, Peter Geoghegan wrote:
> The v4-0001-Remove-hashagg_avoid_disk_plan-GUC.patch changes are
> surprisingly complicated. It would be nice if you could take a look at
> that aspect (or confirm that it's included in your review).
I think you mean "it replaces surprisingly complicated code with
straightforward code". Right? Because in the previous code, there was
a lot of effort going into deciding whether the path needed to be
generated; the new code just generates the path always.
Similarly the code to decide allow_hash in create_distinct_path, which
used to be nontrivial, could (if you wanted) be simplified down to a
single boolean condition. Previously, it was nontrivial only because
it needed to consider memory usage -- not anymore.
But maybe you're talking about something more subtle that I'm just too
blind to see.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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