Re: Table Locking Memory Engine

[Rick James]

If you are using the MEMORY engine, the query cache is probably hurting performance, and should be turned off.

I still need to see SHOW CREATE TABLE.

SHOW VARIABLES LIKE 'innodb%';

Look in the slowlog.

Do SHOW PROCESSLIST several times while the system is busy -- what queries are showing up most often. (Don't show us the output; most of the output is irrelevant.)

> the whole table is deleted and ...
Via DROP TABLE? DELETE * FROM tbl? TRUNCATE TABLE?
There are significant differences in the performance of those three statements.

> $sql = "DELETE FROM $dbname where timeout < $timestamp";
The table in that query needs an index on `timeout`.