Re: Problem with ALTER TYPE, Indexes and cast

Marc Mamin <M(dot)Mamin(at)intershop(dot)de> writes:
> Now I have generated queries that include cast information in order to ensure that the indexes get used.

> e.g.: WHERE month1.foo = cast('XY' as character(2))

> with mixed type, this should become something like:

> SELECT ... FROM month1
> WHERE month1.foo = cast('XY' as character(2))
> UNION ALL
> SELECT... FROM month2
> WHERE month2.foo = cast('XY' as varchar)

> which is quite complicated to resolve in our "query builder framework"

> There seems to be no way to have dynamic casting, something like:

> WHERE month2.foo = cast('XY' as 'month2.foo'::regtype)

> Is there a way for it ?

If the comparison values are always string literals, then you should just
drop the casts altogether, ie

WHERE month2.foo = 'XY'

In this sort of situation the literal's type is preferentially resolved as
being the same as whatever it's being compared to.

regards, tom lane