- Original Message -
From: Andrés Tello mr.crip...@gmail.com
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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