On Jul 5, 2007, at 15:53 , David F. Johnson wrote:
During the development of a database often there is a need to change a field's declaration from, say, VARCHAR(32) to, say, VARCHAR(64).
Is there a simple way to make a user-defined type that is a specific declaration of a built-in type (like VARCHAR(##)) without having to implement the type's support functions?
In PostgreSQL there's no performance advantage to limiting a varchar. I'd recommend making all of your references to any varchar columns not include a limit (i.e., just text or varchar), and perhaps setting the referenced column as text with a length check constraint if one is needed to satisfy some business rule. Then you can easily alter the allowed length by altering the check constraint. (Similarly you could use varchar(n) on the referenced column as well, and then just ALTER TABLE ALTER TYPE instead of altering the check constraint. I don't know if one has a performance advantage in checking the length of the value.)
Michael Glaesemann grzm seespotcode net
