add test cases

tests/system-test/2-query/interp.py

@@ -2382,6 +2382,14 @@ class TDTestCase:
         tdSql.error(f"select interp('abcd') from {dbname}.{tbname} range('2020-02-10 00:00:05', '2020-02-15 00:00:05') every(1d) fill(null)")
         tdSql.error(f"select interp('中文字符') from {dbname}.{tbname} range('2020-02-10 00:00:05', '2020-02-15 00:00:05') every(1d) fill(null)")
 
+        # invalid pseudo column usage
+        tdSql.error(f"select interp(_irowts) from {dbname}.{tbname} range('2020-02-10 00:00:05', '2020-02-15 00:00:05') every(1d) fill(null)")
+        tdSql.error(f"select interp(_isfilled) from {dbname}.{tbname} range('2020-02-10 00:00:05', '2020-02-15 00:00:05') every(1d) fill(null)")
+        tdSql.error(f"select interp(c0) from {dbname}.{tbname} where _isfilled = true range('2020-02-10 00:00:05', '2020-02-15 00:00:05') every(1d) fill(null)")
+        tdSql.error(f"select interp(c0) from {dbname}.{tbname} where _irowts > 0 range('2020-02-10 00:00:05', '2020-02-15 00:00:05') every(1d) fill(null)")
+
+
+
 
         tdLog.printNoPrefix("==========step13:stable cases")