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Fun MySQL fact of the day: too much history

Yesterday, we discussed that InnoDB stores "old" record versions in an undo log, but we didn't discuss where undo logs are stored. While it's amusing to think it's turtles all the way down, it's actually a lot simpler: undo logs are stored inside InnoDB (and in redo logs, ... read more

Fun MySQL fact of the day: nothing isn't free

Nothing isn't free in InnoDB. When a transaction rolls-back in MySQL/InnoDB, the "or-nothing" part of "all-or-nothing" is close to being the most expensive thing you can do in MySQL. While we can dig deep into the internals to find out why, we've already gone over all the building blocks, and ... read more

Fun MySQL fact of the day: all-or-something?

Finally, A. The A in ACID stands for Atomicity, which is the property that guarantees that a series of database operations performed in a transaction all occur or nothing occurs. You might be thinking, "if Atomicity is the first letter in ACID, why did you save it ... read more

Fun MySQL fact of the day: a CHECKered past

A Check Constraint is a table constraint, described in SQL-89, that allows a database index to remain consistent based on a specified search criteria or expression. For example, we could ADD CONSTRAINT is_even_ck CHECK(my_int_col % 2 = 0) to ensure that the value of the my_int_col column in every row ... read more
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