I understand that if a PK is a consecutive number, it will fill a page as its maximum which is a factor of 15/16. If it is a random PK the page fill factor will be of 1/2.
I was wondering if my PK was a composite key.
For example, for a blog post table my PK would be
(author_id, post_id). What fill factor would that use ?
Making a PK of this form lets me retrieve all the posts of a given author faster. But I/O wise I was wondering if this was a good shot.
Question is for MySQL DB using InnoDB storage engine.