Function get_windowfunc_expr

src/backend/utils/adt/ruleutils.c:10309–10379

* get_windowfunc_expr - Parse back a WindowFunc node */

 * get_windowfunc_expr	- Parse back a WindowFunc node
 */
static void
get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
{
	StringInfo	buf = context->buf;
	Oid			argtypes[FUNC_MAX_ARGS];
	int			nargs;
	List	   *argnames;
	ListCell   *l;

	if (list_length(wfunc->args) >= FUNC_MAX_ARGS)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
				 errmsg("too many arguments")));
	nargs = 0;
	argnames = NIL;
	foreach(l, wfunc->args)
	{
		Node	   *arg = (Node *) lfirst(l);

		if (IsA(arg, NamedArgExpr))
			argnames = lappend(argnames, ((NamedArgExpr *) arg)->name);
		argtypes[nargs] = exprType(arg);
		nargs++;
	}

	appendStringInfo(buf, "%s(%s",
					 generate_function_name(wfunc->winfnoid, nargs,
											argnames, argtypes,
											false, NULL,
											context->special_exprkind),
					 wfunc->windistinct ? "DISTINCT " : "");
	/* winstar can be set only in zero-argument aggregates */
	if (wfunc->winstar)
		appendStringInfoChar(buf, '*');
	else
		get_rule_expr((Node *) wfunc->args, context, true);

	if (wfunc->aggfilter != NULL)
	{
		appendStringInfoString(buf, ") FILTER (WHERE ");
		get_rule_expr((Node *) wfunc->aggfilter, context, false);
	}

	appendStringInfoString(buf, ") OVER ");

	foreach(l, context->windowClause)
	{
		WindowClause *wc = (WindowClause *) lfirst(l);

		if (wc->winref == wfunc->winref)
		{
			if (wc->name)
				appendStringInfoString(buf, quote_identifier(wc->name));
			else
				get_rule_windowspec(wc, context->windowTList, context);
			break;
		}
	}