Function prepare_sql_fn_parse_info

src/backend/executor/functions.c:268–352

* Prepare the SQLFunctionParseInfo struct for parsing a SQL function body * * This includes resolving actual types of polymorphic arguments. * * call_expr can be passed as NULL, but then we will fail if there are any * polymorphic arguments. */

 * polymorphic arguments.
 */
SQLFunctionParseInfoPtr
prepare_sql_fn_parse_info(HeapTuple procedureTuple,
						  Node *call_expr,
						  Oid inputCollation)
{
	SQLFunctionParseInfoPtr pinfo;
	Form_pg_proc procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);
	int			nargs;

	pinfo = (SQLFunctionParseInfoPtr) palloc0(sizeof(SQLFunctionParseInfo));

	/* Function's name (only) can be used to qualify argument names */
	pinfo->fname = pstrdup(NameStr(procedureStruct->proname));

	/* Save the function's input collation */
	pinfo->collation = inputCollation;

	/*
	 * Copy input argument types from the pg_proc entry, then resolve any
	 * polymorphic types.
	 */
	pinfo->nargs = nargs = procedureStruct->pronargs;
	if (nargs > 0)
	{
		Oid		   *argOidVect;
		int			argnum;

		argOidVect = (Oid *) palloc(nargs * sizeof(Oid));
		memcpy(argOidVect,
			   procedureStruct->proargtypes.values,
			   nargs * sizeof(Oid));

		for (argnum = 0; argnum < nargs; argnum++)
		{
			Oid			argtype = argOidVect[argnum];

			if (IsPolymorphicType(argtype))
			{
				argtype = get_call_expr_argtype(call_expr, argnum);
				if (argtype == InvalidOid)
					ereport(ERROR,
							(errcode(ERRCODE_DATATYPE_MISMATCH),
							 errmsg("could not determine actual type of argument declared %s",
									format_type_be(argOidVect[argnum]))));
				argOidVect[argnum] = argtype;
			}
		}

		pinfo->argtypes = argOidVect;
	}

	/*
	 * Collect names of arguments, too, if any
	 */
	if (nargs > 0)
	{
		Datum		proargnames;
		Datum		proargmodes;