VACUUM rarely reclaims space from the OS’ perspective, if that’s what you meant. It can in certain circumstances, but they’re rare. VACUUM FULL is the equivalen

VACUUM rarely reclaims space from the OS’ perspective, if that’s what you meant. It can in certain circumstances, but they’re rare. VACUUM FULL is the equivalent to OPTIMIZE TABLE – both lock the table to do a full rewrite, and optimally binpack it to the extent that is posssible. EDIT: my mistake, OPTIMIZE TABLE is an online DDL. I’ve been burned in the past from foreign key constraint metadata locks essentially turning it into a blocking operation.