AW: Strange query execution time

From: Zeugswetter Andreas SB <ZeugswetterA(at)wien(dot)spardat(dot)at>
To: "'Michel Soto'" <Michel(dot)Soto(at)lip6(dot)fr>, pgsql-hackers(at)postgresql(dot)org
Subject: AW: Strange query execution time
Date: 2001-07-05 07:55:04
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> Can someone explain why the following query takes 1 second when using
> LIKE and takes 30 seconds when replacing LIKE by = in the WHERE ?

Because there is no optimization built in, that notices, that your
string does not contain a wildcard and would translate the restriction
correspondingly. It is currently executed more or less like below:
(I3.nameInfluence >= 'inf_vitesse' and I3.nameInfluence < 'inf_vitessf'
and I3.nameInfluence LIKE 'inf_vitesse')
I already wanted to try to add this optimization myself, but lacked the time so far.
Anybody want to volunteer ?

TODO: add LIKE optimization to use = if constant does not contain any wildcards



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