Re: Too Big Created_tmp_disk_tables percent

[Gregory Jablonski]

I found this happening for me too when issuing un-limited select distinct queries, but only when issued against some tables, and not others, that I could never figure out the meaningful difference between.

E.g.

SELECT DISTINCT foo, bar FROM qux WHERE ...

would increment created_tmp_tables and created_tmp_disk_tables every time.

But

SELECT foo, bar FROM qux WHERE ...

would increment neither.

And

SELECT DISTINCT foo, bar FROM qux WHERE ... LIMIT 10000

would increment created_tmp_tables but not created_tmp_disk_tables, even if the LIMIT was set greater than the size of the table (for a relatively small table).