Composite types as parameters

Hello all,

I am trying to add support for composite types to my ORM, which uses libpq
and the binary format.

Given a schema like this one:

create type composite as (...);
create table sometable (field composite, ...);

I want to execute a query like this:

PQexecParams("insert into sometable values($1, ...);", paramValues[0] = serialize some record, ...)

However this fails in coerce_record_to_complex(), because it receives a
node of type Param, but it can only handle RowExpr and Var. There is a
comment suggesting that this is not a fundamental limitation, but (not
being familiar with postgres codebase) I'm not sure how to go about fixing
it. I assume there is a mapping somewhere from param ids to objects, but
am unable to find it.

Does anyone have any pointers or suggestions? Am I going about this in
entirely the wrong way?

-E