"Merlin Moncure" <mmoncure@xxxxxxxxx> writes: > did you have a key on a,b,c? Yeah, I did create index t1i on t1 (a,b,c); Do I need to use some other syntax to get it to work? > select count(*) from (select a,b,max(c) group by a,b) q; > blows the high performance case as does putting the query in a view. I noticed that too, while trying to suppress the returning of the results for timing purposes ... still a few bugs in their optimizer obviously. (Curiously, EXPLAIN still claims that the index is being used.) > mysql> select user_id, acc_id, max(sample_date) from usage_samples group by 1,2 > [...] > +---------+--------+------------------+ > 939 rows in set (0.07 sec) > mysql> select user_id, acc_id, max(sample_date) from usage_samples group by 1,2 > [...] > +---------+--------+------------------+--------------+ > 939 rows in set (1.39 sec) I don't understand what you did differently in those two cases? Or was there a DROP INDEX between? regards, tom lane
