Re: unique index on more than one field using functions

On 22 Jul 2001, Domingo Alvarez Duarte wrote:

> I'm trying create a unique index using more than one field and
> applying a function in one field to achieve case insensitive
> uniqueness but postgresql doesn't accept.
>
> create table a(
>
> id int primary key,
> id2 int not null,
> name varchar(50),
> unique(id2, lower(name))
> );
>
> Anyone have an idea ?

IIRC, Functional indexes are constrained to a single function
with one or more column references (no constants, etc), so
you can't precisely do the above directly. You might be
able to make a function which takes id2 and name and combines
them in some way returning a single varchar and make the unique
index on that result.