Geoff Winkless wrote:
[trying to account for the disk space used]
> Of course I got that slightly wrong: ItemIdData is for each row, not for each column; an extra 4 bytes
> for each row makes the per-row space 290MB, leaving 167MB unexplained.
> I'm assuming the remaining 167MB is related to the alignment requirements, although that does seem
> quite a lot at 15 bytes per row (perhaps I'm just unfortunate with the data sizes resulting in poor
> alignment).
>
> I guess the answer to my question is that there is no answer to my question; pg just does use a
> massive (especially in relation to thin but tall tables) proportion of diskspace for its own purposes.
I doubt that PostgreSQL has substantially more disk overhead
than other DBMS with comparable capabilities (comparison with
flat files or MyISAM would be unfair).
Have you tried using pg_filedump
(http://pgfoundry.org/frs/?group_id=1000541)
to dump a page or two of your table and figure
out what is where and where the space went?
Yours,
Laurenz Albe