Homam S.A. wrote:
> Dropping an index on a MyISAM table should be
> instantaneous. It should only take as long as deleting
> the idx file from the file system. But it's taking
> almost as long as creating the index itself!
> Here's my queries and time they took:
> /*[10:58:17 AM][367172 ms]*/ alter table MyTable add
> index (MyIndex)
> /*[11:20:21 AM][183891 ms]*/ alter table MyTable drop
> index MyIndex
In MySQL, most ALTER TABLE operations involve a full reconstruction of the
table, so dropping a key often takes almost as long as adding one. For a long
time, optimizing them has not been a priority.
Also note that in MyISAM all keys are stored in one MYI file. So dropping a key
is not as easy as just deleting a file.
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