Alternatives to a unique indexes with NULL

From: Peter Hicks <peter(dot)hicks(at)poggs(dot)co(dot)uk>
To: pgsql-general(at)postgresql(dot)org
Subject: Alternatives to a unique indexes with NULL
Date: 2015-01-17 12:27:49
Message-ID: 54BA5545.2080904@poggs.co.uk
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All,

I have a Rails application on 9.3 in which I want to enforce a unique
index on a set of fields, one of which includes a NULL-able column.

According to
http://www.postgresql.org/docs/9.3/static/indexes-unique.html, btree
indexes can't handle uniqueness on NULL columns, so I'm looking for
another way to achieve what I need.

My initial thought is to replace the null with a single space (it's a
character varying(1) column), which will require some changes to
application code, but result in a cleaner process than the application
enforcing the uniqueness constraint.

Is there a better or cleaner way to do what I want?

Peter

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