Tom Lane escribió: > Greg Stark <gsst...@mit.edu> writes: > > It scans pages *backwards* from the end (which does wonderful things > > on rotating media). Marks each live tuple it finds as "moved off", > > finds a new place for it (using the free space map I think?). > > BTW, VACUUM FULL doesn't use the free space map --- that code predates > the FSM by a lot. It builds its own map of free space during its > initial lazy-VACUUM-equivalent scan that just removes dead tuples.
Another weird consequence of this is that it bails out if it finds a tuple larger than it can fit in one of the earlier pages; if there's dead space to be compacted before that, it's not compacted. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
