| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, 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>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Default setting for enable_hashagg_disk |
| Date: | 2020-07-29 17:13:23 |
| Message-ID: | 9f2c09bafc1452f42b8c4131f4f63b8687bd8b3d.camel@j-davis.com |
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| Lists: | pgsql-docs pgsql-hackers |
On Sat, 2020-07-25 at 17:52 -0700, Peter Geoghegan wrote:
> BTW, your HLL patch ameliorates the problem with my extreme "sorted
> vs
> random input" test case from this morning [1] (the thing that I just
> discussed with Tomas). Without the HLL patch the sorted case had 2424
> batches. With the HLL patch it has 20. That at least seems like a
> notable improvement.
Committed.
Though I did notice some overhead for spilled-but-still-in-memory cases
due to addHyperLogLog() itself. It seems that it can be mostly
eliminated with [1], though I'll wait to see if there's an objection
because that would affect other users of HLL.
Regards,
Jeff Davis
[1]
https://www.postgresql.org/message-id/17068336d300fab76dd6131cbe1996df450dde38.camel@j-davis.com
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