"Jay" <arrival123@xxxxxxxxx> 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
