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
InnoDB tries to leave 1/16 of the
page free for future insertions and updates of the index
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 the page.
Changing the page size is not a supported operation and there
is no guarantee that
function normally with a page size other than 16KB. Problems
compiling or running InnoDB may occur.
A version of
InnoDB built for one page size
cannot use data files or log files from a version built for a
different page size.