From: Gregory Stark <stark@enterprisedb.com>
To: Jay <arrival123@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Using PK value as a String
Date: Mon, 11 Aug 2008 10:30:31 +0100
Message-ID: <874p5ruceg.fsf@oxford.xeocode.com> (raw)
In-Reply-To: <9e3be050-8b96-45d9-9bf3-b333bdee0405@i24g2000prf.googlegroups.com>
References: <9e3be050-8b96-45d9-9bf3-b333bdee0405@i24g2000prf.googlegroups.com>
"Jay" <arrival123@gmail.com> writes:
> I have a table named table_Users:
>
> CREATE TABLE table_Users (
> UserID character(40) NOT NULL default '',
> Username varchar(256) NOT NULL default '',
> Email varchar(256) NOT NULL default ''
> etc...
> );
>
> The UserID is a character(40) and is generated using UUID function. We
> started making making other tables and ended up not really using
> UserID, but instead using Username as the unique identifier for the
> other tables. Now, we pass and insert the Username to for discussions,
> wikis, etc, for all the modules we have developed. I was wondering if
> it would be a performance improvement to use the 40 Character UserID
> instead of Username when querying the other tables, or if we should
> change the UserID to a serial value and use that to query the other
> tables. Or just keep the way things are because it doesn't really make
> much a difference.
Username would not be any slower than UserID unless you have a lot of
usernames longer than 40 characters.
However making UserID an integer would be quite a bit more efficient. It would
take 4 bytes instead of as the length of the Username which adds up when it's
in all your other tables... Also internationalized text collations are quite a
bit more expensive than a simple integer comparison.
But the real question here is what's the better design. If you use Username
you'll be cursing if you ever want to provide a facility to allow people to
change their usernames. You may not want such a facility now but one day...
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's On-Demand Production Tuning
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: stark@enterprisedb.com, arrival123@gmail.com
Subject: Re: Using PK value as a String
In-Reply-To: <874p5ruceg.fsf@oxford.xeocode.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox