"Merlin Moncure" <mmoncure@gmail.com> 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