| From: | Andrew - Supernews <andrew+nonews(at)supernews(dot)com> |
|---|---|
| To: | pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Server instrumentation for 8.1 |
| Date: | 2005-05-12 09:43:15 |
| Message-ID: | slrnd8699j.1c8o.andrew+nonews@trinity.supernews.net |
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| Lists: | pgsql-hackers |
On 2005-05-12, Andreas Pflug <pgadmin(at)pse-consulting(dot)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
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