Re: Unique text index on a non-text column

On Fri, Jul 15, 2016 at 10:31 AM, David G. Johnston <
david(dot)g(dot)johnston(at)gmail(dot)com> wrote:

> On Fri, Jul 15, 2016 at 1:26 PM, Craig James <cjames(at)emolecules(dot)com>
> wrote:
>
>> 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.
>
> https://www.postgresql.org/docs/9.6/static/sql-createindex.html
>
> Note the extra set of paretheses surrounding "expression".
>

Ah, I'd overlooked that.

>
> ​create unique index i_unique_molecule on molecules ((cast(moltext as
> text)))
>
> ((moltext::text)) might work...
>

Thanks, that did the trick.

Craig

> David J.
>

--
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Craig A. James
Chief Technology Officer
eMolecules, Inc.
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