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From: Josh Berkus <josh@agliodbs.com>
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: Wei Weng <wweng@kencast.com>, pgsql-performance@postgresql.org
Subject: Re: Does this matter?
Date: Fri, 1 Nov 2002 12:23:48 -0800
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Message-Id: <200211011223.48962.josh@agliodbs.com>

Wei,

> Does it make a performance difference if I use a char(20) or a char(36)
> as the primary key? My thought is no, but I would like to hear more
> opinions.

Yes, it does, though probably minor unless you have millions of records.  C=
HAR=20
is padded out to the specified length.  Therefore the index on a char(36)=
=20
column will be a little larger, and thus a little slower, than the char(20)=
.=20=20

Now, there would be no difference between VARCHAR(20) and VARCHAR(36) unles=
s=20
you used some of the extra 16 characters on most rows.

Either way, for tables of a few thousand records, I doubt that you'll notic=
e=20
the difference.   BTW, why not use a SERIAL value as a surrogate primary ke=
y?

> And a little further off topic(since we have many database experts
> here), does it matter on MS SQL server 7?

Yes, same reason.

--=20
-Josh Berkus
 Aglio Database Solutions
 San Francisco