Re: storage calculations

On Thu, Jul 31, 2003 at 08:51:09AM -0400, pgboy@guthrie.charm.net wrote:
>
> well, i can admit that i am confused. my assumption is that when a row
> is deleted in pg, that row is merely marked as 'gone' until a vacuum-full
> is done. my further assumption is that if i continue to add rows, those
> rows are not necessarily appended to the end of the physical data file,
> but can be written over 'deleted' rows.

Your assumption is wrong.  VACUUM without FULL will allow you to
write over the free space now available in your data files, subject
to the limitations of tracking as determined by your FSM settings.

VACUUM FULL actually shortens the data file.  Except for cases having
to do with large tuples that won't fit in the previous page, VACUUM
FULL means that you can't fit any more data in that file, once the
VACUUM FULL is done.

A

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