Re: At Performance Limit for 2 GB RAM?

[KimSeong Loh]

The 2 primary key are different
(`metadata_id`,`stn_id`,`dich_value`)
(stn_id, metadata_id, dich_value)

The 2nd is able to give you results very fast becasue it is sorted by the stn_id which is able to helps you get all the rows with stn_id = 2500. This should remove the using where in your explain.

Having this primary key may be even better
(stn_id, dich_value, etadata_id)
This will help the "group by dich_value" in your query. This may help remove the using temporary and using filesort in the explain.

Try it and see the difference in the explain result.