Manfred Koizar <mkoi-pg@aon.at> writes:
> Good point. What about: Whenever a backend *deletes* a tuple it
> inserts a reference to its page into the RSM? Then an entry in the
> RSM doesn't necessarily mean that the referenced page has reclaimable
> space, but it would still be valueable information.
That might work if the RSM were lossless, but in practice I think it'd
have to be lossy, like the FSM. Which would mean that you'd still have
to do full-scan vacuums fairly regularly to make sure you hadn't
forgotten any freeable tuples. Conceivably it could be a win, though,
if you could do frequent "vacuum decent"s and only a full-scan vacuum
once in awhile (once a day maybe).
regards, tom lane
