From: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
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To: | David Kerr <dmk(at)mr-paradox(dot)net> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Very high effective_cache_size == worse performance? |
Date: | 2010-04-20 19:22:36 |
Message-ID: | q2udcc563d11004201222se02e858fv50b78b96b9d2c015@mail.gmail.com |
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Lists: | pgsql-performance |
On Tue, Apr 20, 2010 at 12:47 PM, David Kerr <dmk(at)mr-paradox(dot)net> wrote:
> On Tue, Apr 20, 2010 at 02:15:19PM -0400, Robert Haas wrote:
> - On Tue, Apr 20, 2010 at 2:03 PM, David Kerr <dmk(at)mr-paradox(dot)net> wrote:
> - > that thought occured to me while I was testing this. I ran a vacuumdb -z
> - > on my database during the load and it didn't impact performance at all.
> -
> - The window to run ANALYZE usefully is pretty short. If you run it
> - before the load is complete, your stats will be wrong. If you run it
> - after the select statements that hit the table are planned, the
> - updated stats won't arrive in time to do any good.
>
> right, but i'm loading 20 million records in 1000 record increments. so
> the analyze should affect all subsequent increments, no?
I keep thinking FK checks are taking a long time because they aren't
cached because in import they went through the ring buffer in pg or
some other way aren't in a buffer but large effective cache size says
it's 99.99% chance or better that it's in cache, and chooses a poor
plan to look them up. Just a guess.
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