From: "Raj Mathur (=?utf-8?b?4KSw4KS+4KSc?=
	=?utf-8?b?IOCkruCkvuCkpeClgeCksA==?=)" <raju@linux-delhi.org>
Reply-To: raju@linux-delhi.org
Organization: Kandalaya
To: pgsql-sql@postgresql.org
Subject: Re: Generic design: char vs varchar primary keys
Date: Thu, 4 Aug 2011 07:28:25 +0530
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On Thursday 04 Aug 2011, Josh Kupershmidt wrote:
> 2011/8/3 Raj Mathur (=E0=A4=B0=E0=A4=BE=E0=A4=9C =E0=A4=AE=E0=A4=BE=E0=A4=
=A5=E0=A5=81=E0=A4=B0) <raju@linux-delhi.org>:
> > Can you point me to any pages that explain the difference between
> > using, say CHAR(8) vs VARCHAR(8) as the primary key for a table?
> >  Is there any impact on the database in terms of:
> >=20
> > - Speed of indexed retrieval
> > - Speed of join from a referencing table
> > - Storage (I presume VARHAR(8) would have a slight edge, in
> > general) - Any other issue
> I suspect the tiny size differences between char(8) and varchar(8)
> are going to be negligible. In fact, this post talks precisely about
> this concern, and more:
> =20
> http://www.depesz.com/index.php/2010/03/02/charx-vs-varcharx-vs-varc
> har-vs-text/
>=20
> Personally I'd be most worried about the different semantics of the
> types (i.e. treatment of trailing spaces), and perhaps the ease of
> expanding the length constraint in the future.

Thanks, that's useful for benchmarking the various textual data types. =20
Anything specific about using CHAR vs VARCHAR for primary keys that are=20
going to be referenced from multiple tables that comes to mind?

Regards,

=2D- Raj
=2D-=20
Raj Mathur                raju@kandalaya.org      http://kandalaya.org/
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