From: | Dawid Kuroczko <qnex42(at)gmail(dot)com> |
---|---|
To: | "Jim C(dot) Nasby" <decibel(at)decibel(dot)org> |
Cc: | Lincoln Yeoh <lyeoh(at)pop(dot)jaring(dot)my>, Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: Converting MySQL tinyint to PostgreSQL |
Date: | 2005-07-21 14:23:14 |
Message-ID: | 758d5e7f050721072357646781@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
On 7/19/05, Jim C. Nasby <decibel(at)decibel(dot)org> wrote:
> > CREATE TABLE sample1 (
> > a boolean,
> > b int,
> > c boolean
> > );
> >
> > ...it will take more storage than:
> >
> > CREATE TABLE sample2 (
> > b int,
> > a boolean,
> > c boolean
> > );
> >
> Actually, I believe that's the case with just about every database,
I tried making alternating int and boolean fields (8 columns total), and
the loss due to padding was around 30%.
Out of curiosity I repeated the test using MySQL 4.1 MyISAM (alternating
int and tinyint fields versus ints fist, then tinyints) -- the resulting files
had the same size. So, for this case, MySQL MyISAM either reorders
data or stores data without padding.
Regards,
Dawid
> though of course each one has different alignment constraints. The point
> is that I don't know of any database that will silently re-order fields
> under the covers to optimize storage.
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