> Sure -- use CREATE UNIQUE INDEX.
>
> alvherre=# create function singleton(int) returns int immutable language sql
as $$ select 1 $$;
> CREATE FUNCTION
> alvherre=# create table singleton (a int);
> CREATE TABLE
> alvherre=# create unique index only_one on singleton (singleton(a));
> CREATE IND
Alvaro Herrera writes:
> The reason it's not supported in table_constraint, IIUC, is that the
> standard doesn't allow it, and that syntax is standards-mandated.
The real problem is not so much extending the syntax as that there'd be
no way to represent the constraint in information_schema. Excl
Dmitry Fefelov wrote:
> So, deferrable uniques now can be based on column/columns list only. It will
> be very useful if there will be possibility to specify functions in this
> list.
> Is it possible?
Sure -- use CREATE UNIQUE INDEX.
alvherre=# create function singleton(int) returns int imm
On 31 March 2010 06:58, Dmitry Fefelov wrote:
> For now Postgres able to create deferrable uniques with following syntax:
>
> ...
> and table_constraint is:
>
> [ CONSTRAINT constraint_name ]
> { UNIQUE ( column_name [, ... ] ) index_parameters |
> PRIMARY KEY ( column_name [, ... ] ) index_param
For now Postgres able to create deferrable uniques with following syntax:
...
and table_constraint is:
[ CONSTRAINT constraint_name ]
{ UNIQUE ( column_name [, ... ] ) index_parameters |
PRIMARY KEY ( column_name [, ... ] ) index_parameters |
CHECK ( expression ) |
FOREIGN KEY ( column_name
