| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Michael Fuhr <mike(at)fuhr(dot)org> |
| Cc: | ssoo(at)siliconfile(dot)com, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: alter table type from double precision to real |
| Date: | 2007-06-25 04:35:11 |
| Message-ID: | 12671.1182746111@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Michael Fuhr <mike(at)fuhr(dot)org> writes:
> On Mon, Jun 25, 2007 at 09:51:30AM +0900, ssoo(at)siliconfile(dot)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
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