Re: table functions

Eric B.Ridge wrote:
> Let's say I've defined a table function named: myTableFunc() (written in
> C), and that I do this:
>
>    select a, b, c
>       from myTableFunc() as foo (a integer, b varchar(255), c text)
>    where a = 2;
>
> Is it possible for me to get the FROM, WHERE, and AS ... clauses from
> within my table function code?  I'd like to do this so my table function
> can be a little smarter about what it does and what it returns.

You can get the information related to the "as foo (a integer, b varchar(255),
c text)" aka column definition clause. It is passed in to the function. See
contrib/tablefunc/tablefunc.c:connectby_text(). The ReturnSetInfo structure
handed to the function includes a copy of the tupdesc formed by the parser
(expectedDesc).

This capability was added so late in the 7.3 developemnt cycle that I don't
think it is documented anywhere other than the source code and some posts Tom
Lane made to the list (although I'll have to look -- he may have snuck it in
somewhere).

As far as the FROM and WHERE clauses, I don't think there is any information
available to the function. Not sure it would be practical or even possible to
change that -- maybe someone else will comment on this.

Joe