Doubt w.r.t vacuum

Hi,

I was just wondering over it. This is for difference between vacuum full and
vacuum analyze. Can somebody enlighten,

1. IIRC vacuum recovers/reuses dead tuples generated from update but can not do
so for delete? Why?

2. Vacuum full locks entire table, is it possible that it locks a page at a
time and deal with it. It will make vacuum full non-blocking at the cost of
letting it run for a longer time. Or is it that the defragmentation algorithm
needs more than a page?

Just a thought..

Bye
Shridhar

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