| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | flyvholm(at)gfy(dot)ku(dot)dk |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: SQL - planet redundant data |
| Date: | 2005-09-09 04:41:17 |
| Message-ID: | 441.1126240877@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Poul Jensen <flyvholm(at)gfy(dot)ku(dot)dk> writes:
> One thought: PostgreSQL adds to every table a system column tableoid
> containing a constant value. Is that value really stored 1,000 times for
> a 1,000-row table? Or...?
No, tableoid is sort of a virtual column ... it doesn't exist on disk.
When you query it you get a value fetched from the internal data
structure representing the table.
There is plenty of *real* overhead per row, mind you, but tableoid isn't
part of it. You can read some details here:
http://developer.postgresql.org/docs/postgres/storage-page-layout.html
regards, tom lane
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