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From:Johan De Meersman Date:November 28 2012 9:02am
Subject:Re: Still struggling witn like 'CTV%' over varchar.... I simple
cannot understand..
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----- Original Message -----
> From: "Andrés Tello" <mr.criptos@stripped>
>
> showed the usage of the index, then, some time later, it show, for
> the same query, the usage of no index...

Look at the "rows" field. It's obvious that this table is live and rather on the active
side; and the data has changed in such a way that on the second explain, the optimizer
estimates that there would be little benefit from using that key - most likely due to
cardinality.

Make a copy of the table so your data is static, and you'll get the same explain every
time. That will, however, apparently not simulate the real world for you.

If this is a MyISAM table you may need to run ANALYZE TABLE to update the statistics; or
you may just have to accept that the same query on different data may benefit from a
different execution plan - just as a different query on the same data would.


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Thread
Still struggling witn like 'CTV%' over varchar.... I simple cannot understand..AndrĂ©s Tello28 Nov
  • Re: Still struggling witn like 'CTV%' over varchar.... I simplecannot understand..Johan De Meersman28 Nov