Re: TODO list request: FK to unique expression indexes - Mailing list pgsql-hackers

On Nov 19, 2008, at 9:12 AM, Josh Berkus wrote:

> Folks,
>
> Since it's too late to look at this for 8.4, can the following go on  
> the TODO list?
>
> Referential Integrity
>
> [] Allow creation of FKs targeting unique expression indexes on the  
> referenced table.  Syntax: REFERENCES <reftable> ( ( column  
> expression ) )
>
> Reason: current FK rules do not allow creating FKs to columns which  
> are defined as, for example, unique(lower(column)).  This forces  
> users to either abandon RI for that table, to store duplicate data,  
> or create superfluous indexes.
>
> Hmmm ... I suppose the above would require enabling expression  
> indexes for PKs as well, no?

In 8.4 you should be able to get around this particular example using  
citext.

Best,

David