Fix the incorrect string limit when declaring NVARCHAR(Max) (#482)

Previously, the limit on the max length of NVARCHAR(Max) was 4000, longer characters will be truncated. But
NVARCHAR(MAX) should be capable of handling strings far longer than 4,000 characters. This pr change the column
size to default -1 (0xffff).

Task: BABEL-5054
Signed-off-by: Chenxiao Wang <[email protected]>

src/backend/utils/adt/jsonpath_exec.c

@@ -573,7 +573,7 @@ tsql_openjson_with_columnize(Jsonb *jb, char *col_info)
 		if (token)
 		{
 			token = strtok(NULL, ")");
-			if (token)
+			if (token && atoi(token) > 0)
 				col_size = atoi(token);
 		}
 	}