| From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: new autovacuum criterion for visible pages |
| Date: | 2016-08-12 13:15:48 |
| Message-ID: | 90960589-eb00-e973-0711-e9e4581d6ae9@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 8/11/16 11:59 AM, Jeff Janes wrote:
> Insertions and HOT-updates clear vm bits but don't increment the
> counters that those existing parameters are compared to.
>
> Also, the relationship between number of updated/deleted rows and the
> number of hint-bits cleared can be hard to predict due to possible
> clustering of the updates into the same blocks. So it would be hard
> to know what to set the values to.
Well, the current threshold formulas aren't an exact science either.
They just trigger autovacuum often enough relative to table size and
activity. Just fudging in the insert and HOT update counters times some
factor might be enough, and it would get this functionality out to all
users without more effort.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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