Changing storage engine rebuild table change file per table

For example, if t1 is currently not an InnoDB table, this statement changes its storage engine to InnoDB:

ALTER TABLE t1 ENGINE = InnoDB;

If the table is already InnoDB, this will rebuild the table and its indexes and have an effect similar to OPTIMIZE TABLE. You may gain some disk space improvement.

If the value of innodb_file_per_table is currently different than the value in effect when t1 was built, this will convert to (or from) file_per_table.