Re: is it possible to make this faster?

"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