Function generate_function_name

src/backend/utils/adt/ruleutils.c:12127–12219

* generate_function_name * Compute the name to display for a function specified by OID, * given that it is being called with the specified actual arg names and * types. (Those matter because of ambiguous-function resolution rules.) * * If we're dealing with a potentially variadic function (in practice, this * means a FuncExpr or Aggref, not some other way of calling a function), then *

 * The result includes all necessary quoting and schema-prefixing.
 */
static char *
generate_function_name(Oid funcid, int nargs, List *argnames, Oid *argtypes,
					   bool has_variadic, bool *use_variadic_p,
					   ParseExprKind special_exprkind)
{
	char	   *result;
	HeapTuple	proctup;
	Form_pg_proc procform;
	char	   *proname;
	bool		use_variadic;
	char	   *nspname;
	FuncDetailCode p_result;
	Oid			p_funcid;
	Oid			p_rettype;
	bool		p_retset;
	int			p_nvargs;
	Oid			p_vatype;
	Oid		   *p_true_typeids;
	bool		force_qualify = false;

	proctup = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
	if (!HeapTupleIsValid(proctup))
		elog(ERROR, "cache lookup failed for function %u", funcid);
	procform = (Form_pg_proc) GETSTRUCT(proctup);
	proname = NameStr(procform->proname);

	/*
	 * Due to parser hacks to avoid needing to reserve CUBE, we need to force
	 * qualification in some special cases.
	 */
	if (special_exprkind == EXPR_KIND_GROUP_BY)
	{
		if (strcmp(proname, "cube") == 0 || strcmp(proname, "rollup") == 0)
			force_qualify = true;
	}

	/*
	 * Determine whether VARIADIC should be printed.  We must do this first
	 * since it affects the lookup rules in func_get_detail().
	 *
	 * We always print VARIADIC if the function has a merged variadic-array
	 * argument.  Note that this is always the case for functions taking a
	 * VARIADIC argument type other than VARIADIC ANY.  If we omitted VARIADIC
	 * and printed the array elements as separate arguments, the call could
	 * match a newer non-VARIADIC function.
	 */
	if (use_variadic_p)
	{
		/* Parser should not have set funcvariadic unless fn is variadic */
		Assert(!has_variadic || OidIsValid(procform->provariadic));
		use_variadic = has_variadic;
		*use_variadic_p = use_variadic;
	}
	else
	{
		Assert(!has_variadic);
		use_variadic = false;
	}