Re: EXCLUDE constraint with not equals

> Given the following table, I would like to ensure that all the rows for an
> email that have a user defined map to the same user.
>
> CREATE TABLE person (
> id INTEGER PRIMARY KEY,
> user TEXT,
> email TEXT NOT NULL);
>
>
> What I think I'm looking for is something like this:
>
> CREATE TABLE person (
> id INTEGER PRIMARY KEY,
> user TEXT,
> email TEXT NOT NULL,
> EXCLUDE (email WITH =, user WITH <>)
> WHERE (user IS NOT NULL));
>
> The not equals comparison isn't supported, but it would be useful here.
>
> Is there another way to do this, short of creating a separate table that
> associates email and user?

You can use the btree_gist extension from contrib:

CREATE EXTENSION btree_gist;

CREATE TABLE person (
id INTEGER PRIMARY KEY,
"user" TEXT,
email TEXT NOT NULL,
EXCLUDE USING gist (email WITH =, "user" WITH <>)
WHERE ("user" IS NOT NULL));