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Re: Sort Performance
Posted by: Peter Zaitsev
Date: November 05, 2004 12:46AM

Hi,

Could you pleas provide EXPLAIN for both queries ?
SHOW CREATE TABLE for table in question would also be helpful.

Sorting 5 rows should not take that much so there is something else out where.

One of the possibilities is - MySQL would do scan in index order to resolve the query
instead of doing filesort - this is good idea if LIKE clause matches a lot of rows but is bad
if it matches just few rows. As you have LIKE "%const%" MySQL is not able to estimate how many rows will match. In such case IGNORE INDEX (security) hint should help this query.

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