Today’s blog post starts with a question:

“In my continuous integration environment, running tests currently takes 30 minutes. I
believe that a large percentage of time is spent in MySQL, and I want to know if putting MySQL
on tmpfs will cut that time down?”.

I have previously written about how to configure MySQL to be less durable in testing environments, but today I wanted to write about how we can really test the assumption that the question is based around. That is to say:

• We know that total time is 30 minutes.
• We assume MySQL is a large percentage of this.
• We know that this optimization will potentially allow us to avoid IO.
• We then want to know what amount of time MySQL spends waiting on IO during our test suite?

And the answer to …

The MySQL error log has received some attention in MySQL 5.7, with a new setting called log_error_verbosity.

There are three possible values, as documented in the manual:

As Giuseppe has written about previously, writing notes or “informational events” can create debugging problems because they reduce the …