On Fri, 22 Aug 2003 12:15:33 +0530, "Shridhar Daithankar"
<shridhar_daithankar@persistent.co.in> wrote:
>> Which leads us to a zero gravity vacuum, that does the lazy vacuum for
>> pages currently available in the buffer cache only. [...]
>
>Since autovacuum issues vacuum analyze only, is it acceptable to say that this
>is taken care of already?
Even a plain VACUUM (without FULL) scans the whole relation to find
the (possibly few) pages that need to be changed. We are trying to
find a way to avoid those needless reads of clean pages, because (a)
they are IOs competing with other disk operations and (b) they push
useful pages out of OS cache and (c) of PG shared buffers. The latter
might become a non-issue with LRU-k, 2Q or ARC. But (a) and (b)
remain.
Servus
Manfred
