Re: index not used afer VACUUM ANALYZE

From: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>
To: mike <mike(at)Reifenberger(dot)com>
Cc: <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: index not used afer VACUUM ANALYZE
Date: 2003-08-25 07:43:56
Message-ID: 20030825004313.V79187-100000@megazone.bigpanda.com
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On Thu, 21 Aug 2003, mike wrote:

> Hi,
> I hav a db as specified in nit.sql
> flows has 763488 entries.
>
> After dropping/creating/loading the db and running auswert.sh I get
> the attached result from query1.txt.
> After 'VACUUM ANALYZE' I get the results from query2.txt
>
> As you can see, the indexes are not used any longer.
> Why?

It looks like the row estimates changed to say that a large % of the rows
match the condition. Is that true? In any case, what does EXPLAIN
ANALYZE rather than EXPLAIN say for the various queries?

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