| From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: HOT pgbench results |
| Date: | 2007-08-07 14:40:12 |
| Message-ID: | 46B8844C.2050506@enterprisedb.com |
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| Lists: | pgsql-hackers |
Tom Lane wrote:
> Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
>> unpatched HOT
>> autovacuums 116 43
>> autoanalyzes 139 60
>
>> HOT greatly reduces the number of vacuums needed. That's good, that's
>> where the gains in throughput in longer I/O bound runs comes from.
>
> But surely failing to auto-analyze after a HOT update is a bad thing.
Hmm, I suppose. I don't think we've spend any time thinking about how to
factor in HOT updates into the autovacuum and autoanalyze formulas yet.
I'd argue that HOT updates are not as significant as cold ones from
statistics point of view, though, because they don't change indexed
columns. HOT-updated fields are not likely used as primary search quals.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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