| From: | Greg Smith <greg(at)2ndquadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Hussey <peter(at)labkey(dot)com>, pgsql-performance <pgsql-performance(at)postgresql(dot)org>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Subject: | Re: Questions on query planner, join types, and work_mem |
| Date: | 2010-08-04 20:38:32 |
| Message-ID: | 4C59CFC8.4000701@2ndquadrant.com |
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| Lists: | pgsql-performance |
Kevin Grittner wrote:
> Assuming this is real, and not just "in the noise" -- what conclusions would you
> draw from this?
Was trying to demonstrate the general ability of pg_stat_bgwriter
snapshots at points in time to directly measure the buffer activity
Hannu was theorizing about, not necessarily show a useful benchmark of
any sort with that. Watching pgbench create a database isn't all that
interesting unless you either a) increase the database scale such that
at least one timed checkpoint kicks in, or b) turn on archive_mode so
the whole WAL COPY optimization is defeated. More on this topic later,
just happened to have that little example script ready to demonstrate
the measurement concept.
--
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com www.2ndQuadrant.us
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