InnoDB’s checkpoint algorithm is not well documented. It is too complex to explain in even a long blog post, because to understand checkpoints, you need to understand a lot of other things that InnoDB does. I hope that explaining how InnoDB does checkpoints in high-level terms, with simplifications, will be helpful. A lot of the simplifications are because I do not want to explain the complexities of how the simple rules can be tweaked for optimization purposes, while not violating the ACID guarantees they enforce.

A bit of background: Gray and Reuter’s classic text on transaction processing introduced two types of checkpoints beginning on page 605. There is a sharp checkpoint, and there is a fuzzy checkpoint.

A sharp checkpoint is accomplished by