Re: updating all records of a table

you might consider lowering the fillfactor a bit. It will consume more
space, but it will make updates and inserts faster.

http://www.postgresql.org/docs/8.4/interactive/sql-createtable.html :
fillfactor (integer)

The fillfactor for a table is a percentage between 10 and 100. 100 (complete
packing) is the default. When a smaller fillfactor is specified,
INSERT operations
pack table pages only to the indicated percentage; the remaining space on
each page is reserved for updating rows on that page. This gives UPDATE a
chance to place the updated copy of a row on the same page as the original,
which is more efficient than placing it on a different page. For a table
whose entries are never updated, complete packing is the best choice, but in
heavily updated tables smaller fillfactors are appropriate. This parameter
cannot be set for TOAST tables.
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