Re: dblink: add polymorphic functions.

Joe Conway <mail(at)joeconway(dot)com> writes:
> What about just TYPE then?

> SELECT x::TYPE(some_expression) FROM ...
> SELECT CAST (x AS TYPE(some_expression)) FROM ...

Yeah, that would work. Quick-hack proof-of-concept patch attached.
Some usage examples in the regression database:

regression=# select pg_typeof(43::type(q1)) from int8_tbl;
pg_typeof
-----------
bigint
bigint
bigint
bigint
bigint
(5 rows)

regression=# select pg_typeof(43::type(q1/0.0)) from int8_tbl;
pg_typeof
-----------
numeric
numeric
numeric
numeric
numeric
(5 rows)

regression=# select pg_typeof(43::type(f1)) from point_tbl;
ERROR: cannot cast type integer to point
LINE 1: select pg_typeof(43::type(f1)) from point_tbl;
^

The main limitation of this patch is that it won't work for call sites
that pass pstate == NULL to LookupTypeName. There are a fair number
of them, some of which wouldn't care because they could never invoke
this notation anyway, but for others we'd need to do some work to cons
up a suitable pstate.

regards, tom lane