Re: Server instrumentation for 8.1

On 2005-05-12, Andreas Pflug <pgadmin@pse-consulting.de> wrote:
> Andrew - Supernews wrote:
>> dbsize looks at the actual size of files on disk; newsysviews does not,
>> it shows estimated sizes as taken from relpages.
>
> Which shows *net* size only, not actual size because non-vacuumed rows 
> are not covered. It is correct after a vacuum full only.

nonsense

relpages is updated from the value of RelationGetNumberOfBlocks(rel) which
is definitive (it gets the value from smgr which gets it from the physical
file sizes); the only inaccuracy is that it is correct only as of the time
that the pg_class row was last updated (as done by any VACUUM, any ANALYZE,
any CLUSTER or any CREATE INDEX on the table, at minimum).

-- 
Andrew, Supernews
http://www.supernews.com - individual and corporate NNTP services