sql - Free space in MySQL after deleting tables & columns?

Question

I have a database of around 20GB. I need to delete 5 tables & drop a few columns in some other 3 tables.

Dropping 5 tables with free some 3 GB and dropping columns in other tables should free another 8GB.

How do I reclaim this space from MySQL.

I've read dumping the database and restoring it back as one of the solution but I'm not really sure how that works, I am not even sure if this only works for deleting the entire database or just parts of it?

Please suggest how to go about this. THanks.

Answer 1

From the comments, it sounds like you're using InnoDB without the file per table option.

Reclaiming space from the innodb tablespace is not generally possible in this mode. Your only course of action is to dump the whole database, turn on file-per-table mode, and reload it (with a completely clean mysql instance). This is going to take a long time with a large database; mk-parallel-dump and restore tools might be a bit quicker, but it will still take a while. Be sure to test this process on a non-production server first.