Обсуждение: Typecast a user-defined type?

Hi,

I've created my own datatype for Postgres. I have found it necessary to be
able to convert it to text, so I could match it up with a text column in a
UNION. I figured Postgres would do this for me, but then, I'm naive. Can
someone give me a hint, or point me to the appropriate material on how to get
"value::text" to work with my new type?

Thanks,
Mark

Mark Volpe <volpe.mark@epamail.epa.gov> writes:
> someone give me a hint, or point me to the appropriate material on how to get
> "value::text" to work with my new type?

Write a function "text(yourtype) RETURNS text", and the parser will use
it for type coercions from yourtype to text.  In general any type
coercion can be provided this way --- a function of a single argument,
having the same name as its return type, represents a coercion path.
        regards, tom lane