[SOLVED] In PostgreSQL, How can I identify a type is composite based on its type Oid in C function?

In PostgreSQL, How can I identify a type is composite based on its type Oid in C function?

I am writing a trigger with C in PostgreSQL that would need to identify whether the type is composite or not based on its Oid in pg_type.

It is one of the few information that is not included in FormData_pg_attribute structure.

Can anyone help? Thanks a lot.

Solution

You could proceed like this (untested):

#include "access/htup.h"
#include "catalog/pg_type.h"
#include "utils/syscache.h"

bool is_composite(Oid typoid)
{
    HeapTuple   tup;
    Form_pg_type typtup;
    bool result;

    tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typoid));
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "cache lookup failed for type %u", basetypoid);
    typtup = (Form_pg_type) GETSTRUCT(tup);

    result = (typtup->typtype == TYPTYPE_COMPOSITE);

    ReleaseSysCache(tup);

    return result;
}