I'd like to enforce text uniqueness on a non-text column (it's of type "molecule" from a third-party plugin). The third-party plugin doesn't support unique indexes. My guess was something like this, but it doesn't work:create table molecules(id integer primary key, moltext molecule('my-type'));create unique index i_unique_molecule on molecules(moltext::text);The "molecule" column does contain an ordinary string, and when selected returns ordinary text data.Is there a way to do this? (And if so, what did I miss in the documentation?)
It helps to show what "doesn't work" actually is.
Note the extra set of paretheses surrounding "_expression_".
create unique index i_unique_molecule on molecules ((cast(moltext as text)))
((moltext::text)) might work...
David J.
