Re: alter table type from double precision to real - Mailing list pgsql-general

Michael Fuhr <mike@fuhr.org> writes:
> On Mon, Jun 25, 2007 at 09:51:30AM +0900, ssoo@siliconfile.com wrote:
>> But PostgreSQL's data disk usage did not shrinked.
>> And pg_dump size remained same.
>> It seems that real takes 8 byte storage sizes.

> Real is 4 bytes but other columns' alignment requirements might
> result in no space being saved.

Even with no other columns involved, if you're on a machine with
MAXALIGN = 8 (which includes all 64-bit platforms as well as some
that aren't), the row width won't shrink.

As for that pg_dump measurement, the text form isn't going to get
smaller ... "1.2" is the same length as "1.2".

            regards, tom lane