MySQL Not Recovered After Running Out of Space

Given this is a Windows installation, @DTest still provided the initial proper direction.

Apply the following formula:

Most people use this:

Maximum MySQL Memory Usage = innodb_buffer_pool_size + key_buffer_size + (read_buffer_size + sort_buffer_size) X max_connections

I prefer this:

Maximum MySQL Memory Usage = innodb_buffer_pool_size + key_buffer_size + ((read_buffer_size + read_rnd_buffer_size + sort_buffer_size + join_buffer_size) X max_connections)

These variables are the ones you need to adjust until the formula yields 80% of installed RAM or less.

sort_buffer_size
read_buffer_size
read_rnd_buffer_size
join_buffer_size
max_connections

1. This sounds like a perfect use of TRIGGERS to me. You say you have transactions, so you must already be using InnoDB. Attach triggers on INSERT, UPDATE, and DELETE on the tables you care about, each one triggering an INSERT into a log table AFTER the table event. There's your SELECT filter, done. You also have total control over what you log and how.

   This is a higher level solution, closer to the application layer, not a low-level system log solution where you have an exact copy of the complete SQL query. But I think it does address some of your concerns.

   InnoDB Triggers have access to stored procedures and all the MySQL functions, so I presume you can find the user's login name in there somewhere. The log time is just NOW().

   You may end up with a lot of triggers to manage, depending on your number of tables, but it's just a copy/paste job for each one. I maintain the code for all triggers in a single reference SQL file along with the table definitions and views for that database.

   I've never tested triggers in a transaction-rich environment to make sure the trigger only fired after the transaction was committed. The docs are thin on this subject, but they do say, "An AFTER trigger is executed only if the BEFORE trigger (if any) and the row operation both execute successfully." Sounds conclusive to me. Now you also know you're not logging things that didn't actually work.

2. OR set up replication, even to another mysqld instance on the same box if necessary. Turn on your mysqld full query logging on the slave instance. Failed transactions don't get replicated, and neither do SELECTs.