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Re: Big differences in plans between 8.0 and 8.1

From: Joe Conway <mail(at)joeconway(dot)com>
To: Gabriele Turchi <gabriele(dot)turchi(at)l39a(dot)com>
Cc: Michael Fuhr <mike(at)fuhr(dot)org>, pgsql-performance(at)postgresql(dot)org, Marco Colombo <marco(at)esiway(dot)net>
Subject: Re: Big differences in plans between 8.0 and 8.1
Date: 2006-07-16 18:08:07
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
Gabriele Turchi wrote:
> Il giorno sab, 15/07/2006 alle 13.04 -0700, Joe Conway ha scritto:
>>Why not just periodically (once an hour?) run "ANALYZE registrazioni;" 
>>during the day. This will only update the statistics, and should be very 
>>low impact.
> This is my "solution" too... but: is enough? Or else: there is a better
> way to do this? If the performance in the better case is 50 times faster
> than the worse case, during an hour (50/100 record inserted in
> "registrazioni") how much the performance can fall before the new
> "ANALYZE" is run? Otherwise, running ANALYZE more frequently can badly
> affect the overall performance?

One thing I noticed is that in both plans there is a seq scan on 
registrazioni. Given that performance degrades so quickly as records are 
inserted into registrazioni, I'm wondering if you're missing an index. 
What indexes do you have on registrazioni?


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