I’ve been researching how to optimize only fragmented tables in MySQL and reviewed this post on optimizing tables. It basically performs a query against the information_schema database for any table with data_free > 0
and builds a SQL statement to OPTIMIZE
only those tables. I ran this query and it identified 148 tables for optimization. All of the tables identified are InnoDB tables. After executing the resultant optimization SQL script, I re-ran the original script to identify fragmented tables and it returned the exact same tables during the first pass.
I have seen conflicting posts regarding the InnoDB tables and the OPTIMIZE
command. Some say that OPTIMIZE
will not work with InnoDB tables and that you need to run ALTER TABLE table_name ENGINE=INNODB
. Others say that OPTIMIZE
actually calls the ALTER TABLE
command when executing against InnoDB tables. With that in mind, I ran the ALTER TABLE
command against one of the InnoDB tables identified as being fragmented (data_free > 0
) and found that the data_free
did not change afterwards. It’s still greater than 0. I also re-started MySQL and checked it only to find the same results.
Now, we have several servers running MySQL 5.5.29 in our organization and I ran a query against all of them to identify any InnoDB tables with DATA_FREE=0 or NULL
and none were returned. They are all greater than zero.
I also ran the OPTIMIZE
command against a few MyISAM
tables where DATA_FREE
was greater than zero and verify that it was zero afterwards.
Can anyone shed some light on this for me? What is the proper method to remove fragmentation from InnoDB tables? What is the proper method to determine fragmented InnoDB tables?
Thanks