Function IsThereFunctionInNamespace

src/backend/commands/functioncmds.c:2565–2580

* Subroutine for ALTER FUNCTION/AGGREGATE SET SCHEMA/RENAME * * Is there a function with the given name and signature already in the given * namespace? If so, raise an appropriate error message. */

 * namespace?  If so, raise an appropriate error message.
 */
void
IsThereFunctionInNamespace(const char *proname, int pronargs,
						   oidvector *proargtypes, Oid nspOid)
{
	/* check for duplicate name (more friendly than unique-index failure) */
	if (SearchSysCacheExists3(PROCNAMEARGSNSP,
							  CStringGetDatum(proname),
							  PointerGetDatum(proargtypes),
							  ObjectIdGetDatum(nspOid)))
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_FUNCTION),
				 errmsg("function %s already exists in schema \"%s\"",
						funcname_signature_string(proname, pronargs,
												  NIL, proargtypes->values),
						get_namespace_name(nspOid))));
}

/*
 * ExecuteDoStmt