From: PFC <lists@boutiquenumerique.com>
To: tjo@acm.org
To: pgsql-sql@postgresql.org
Subject: Re: testing/predicting optimization using indexes
Date: Wed, 26 Jan 2005 22:45:19 +0100
Message-ID: <opsk8b1tmpth1vuj@musicbox> (raw)
In-Reply-To: <41F1A387.5040402@acm.org>
References: <41F1A387.5040402@acm.org>
> I'm quite happy with the speedup in 3, but puzzled over the slowdown in
> 2.
Could you provide :
- SELECT count(*) FROM structure;
=> NRows
- SELECT avg(length(smiles)) FROM structure;
Then VACUUM FULL ANALYZE structure
Redo your timings and this time post EXPLAIN ANALYZE
Also your query returns 1313 rows, so wan you post :
EXPLAIN ANALYZE SELECT oe_matches(smiles,'c1ccccc1CC(=O)NC') FROM
structure;
=> time T1
EXPLAIN ANALYZE SELECT smiles FROM structure;
=> time T2
(T1-T2)/(NRows) will give you an estimate of the time spent in each
oe_matches call.
Also note that for postgres (a,b) > (c,d) means ((a>c) and (b>d)), which
can be misleading, but I think that's what you wanted.
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To: pgsql-sql@postgresql.org
Cc: lists@boutiquenumerique.com, tjo@acm.org
Subject: Re: testing/predicting optimization using indexes
In-Reply-To: <opsk8b1tmpth1vuj@musicbox>
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