[TD-2627]<test> add case for apercentile

tests/pytest/functions/function_percentile.py

@@ -142,6 +142,15 @@ class TDTestCase:
         tdSql.error("select percentile(voltage, 20) from meters")
         tdSql.query("select apercentile(voltage, 20) from meters")
         print("apercentile result: %s" % tdSql.getData(0, 0))
+
+        # Test case for: https://jira.taosdata.com:18080/browse/TD-2609
+        # modified for : https://jira.taosdata.com:18080/browse/TD-2627
+        tdSql.execute("create table st(ts timestamp, k int)")
+        tdSql.execute("insert into st values(now, -100)(now+1a,-99)")
+        tdSql.query("select apercentile(k, 20) from st")
+        tdSql.checkData(0, 0, -100.00)
+
+
         
     def stop(self):
         tdSql.close()