I set my MySQL
tmpdir setting to use
/run/mysqld which is a
tmpfs, however while running a query I know copies data to a temp table (which takes 5-6 seconds based on MySQL's
INFORMATION_SCHEMA.PROFILE records) I am not seeing any temporary file(s) being written out to that directory when doing an
ls -la at the command prompt.
Additionally, the query speed did not change when moving my tmpdir from an on-disk location to an in memory location (tmpfs) which it clearly should have improved.
Question: How do I know for sure that my tmpdir is being used?