InnoDB indexes are
B-trees where the index records
are stored in the leaf pages of the tree. The default size of an
index page is 16KB.
When new records are inserted into an
InnoDB tries to leave 1/16 of the page free for
future insertions and updates of the index records. If index
records are inserted in a sequential order (ascending or
descending), the resulting index pages are about 15/16 full. If
records are inserted in a random order, the pages are from 1/2 to
15/16 full. If the fill
factor of an index page drops below 1/2,
InnoDB tries to contract the index tree to free
You can define the page size
InnoDB tablespaces in a MySQL instance
by setting the
configuration option prior to initializing the MySQL instance.
Once the page size for an instance is defined, you cannot change
it without reinitializing the instance. Supported sizes are 16KB,
8KB, and 4KB.
A MySQL instance using a particular
size cannot use data files or log files from an instance that uses
a different page size.