The docs include a handy articulation of fixes.
> This scenario is essentially identical to one in which there's a single migration statement that requires an `AccessExclusiveLock` and performs a table rewrite, such as adding a NOT NULL column with a DEFAULT value.
Unless the `DEFAULT` value is `VOLATILE` (this is rarely the case as usually default values are at least `STABLE`) no table rewrite is necessary since Postgres 11.
https://www.postgresql.org/docs/devel/sql-altertable.html
> Many other useful performance improvements, including the ability to avoid a table rewrite for ALTER TABLE ... ADD COLUMN with a non-null column default
Another appear of an ax in a Pink Floyd song is the “ Run to the bedroom, in the suitcase on the left, you'll find my favorite axe,” from “One Of My Turns”
