Обсуждение: Unique text index on a non-text column

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Unique text index on a non-text column

От
Craig James
Дата:
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?)

Thanks,
Craig

Re: Unique text index on a non-text column

От
"David G. Johnston"
Дата:
On Fri, Jul 15, 2016 at 1:26 PM, Craig James <cjames@emolecules.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.


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.

Re: Unique text index on a non-text column

От
Craig James
Дата:
On Fri, Jul 15, 2016 at 10:31 AM, David G. Johnston <david.g.johnston@gmail.com> wrote:
On Fri, Jul 15, 2016 at 1:26 PM, Craig James <cjames@emolecules.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.


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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