Hello,
Perhaps I don't understand indexes but I was wondering how to improve teh
performance of a query on an indexed column that uses MAX().
mysql> explain select max(master_mtime) from redirects where uri_scheme =
'http';
+-----------+------+-----------------------------+----------------+---------+-------+---------+------------+|
+ table | type | possible_keys | key | key_len
| ref | rows | Extra |
+-----------+------+-----------------------------+----------------+---------+-------+---------+------------+|
+ redirects | ref | full_uri_idx,uri_scheme_idx | uri_scheme_idx | 16
| const | 7694050 | where used |
+-----------+------+-----------------------------+----------------+---------+-------+---------+------------+1
+ row in set (0.01 sec)
There is an index on master_mtime but it's not listed by explain???
Perhaps MAX() uses the sort buffer? If so, how can I work out what to
increase the sort buffer to, aside from guessing.
Thanks for any help
Richard
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