MySQL find unused tables

Question

I am working with a database which unfortunately has a lot of unused tables and I am trying to clean it up. I'm trying to find a way where I can be 100% confident that a particular table is no longer being used.

After some googling, I still cannot find a good way to do so. I am only able to tell the last writes to a table (INSERT, UPDATE, etc) using:

SHOW TABLE STATUS or running ls -lt on the mysql datadir (can be found by by running SHOW VARIABLES LIKE 'datadir';)

Do you have any other suggestions?

Thanks.

Answer 1

Try using the INFORMATION_SCHEMA.TABLES

There is a column called UPDATE_TIME

Check the date in that field

If it is NULL, the table has never been updated since the table's creation

Example : A list of tables not updated in the last 10 days

select table_schema,table_name,create_time,update_time from information_schema.tables where table_schema not in ('information_schema','mysql') and engine is not null and ((update_time < (now() - interval 10 day)) or update_time is null);

Give it a try !!!

Answer 2

Try that http://forums.mysql.com/read.php?20,298759,299185#msg-299185

Turning on the "general log" and scanning it (programatically!) would tell you who is hitting what tables during the time the log is on. Caution: that file grows fast.

Answer 3

I know this is an old question, but there doesn't seem to be a proper answer and I was directed here by my own search for an answer. As per Mark Leith's blog post about unused tables and indexes one should be able to do something like this:

SELECT
    t.*
FROM performance_schema.table_io_waits_summary_by_table t
WHERE
    t.COUNT_STAR = 0
    AND t.OBJECT_SCHEMA = '<your-schema-name-goes-here>'
    AND t.OBJECT_TYPE = 'TABLE';

Official documentation about the topic from MySQL gives more details.

It does of course require that you've enabled Performance Schema and that the statistics haven't been cleared/truncated for some time.