[DRILL-3783] Incorrect results : COUNT(<column-name>) over results returned by UNION ALL

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Not A Problem
• Affects Version/s: 1.2.0
• Fix Version/s: 1.2.0
• Component/s: Execution - Relational Operators

Environment

4 node cluster on CentOS

• Assignee: Khurram Faraaz
• Reporter: Khurram Faraaz
• Created: 15/Sep/15 18:20
• Updated: 16/Sep/15 17:26
• Resolved: 16/Sep/15 16:19

Description

Count over results returned union all query, returns incorrect results. The below query returned an Exception (please se DRILL-2637) that JIRA was marked as fixed, however the query returns incorrect results.

0: jdbc:drill:schema=dfs.tmp> select count(c1) from (select cast(columns[0] as int) c1 from `testWindow.csv`) union all (select cast(columns[0] as int) c2 from `testWindow.csv`);
+---------+
| EXPR$0  |
+---------+
| 11      |
| 100     |
| 10      |
| 2       |
| 50      |
| 55      |
| 67      |
| 113     |
| 119     |
| 89      |
| 57      |
| 61      |
+---------+
12 rows selected (0.753 seconds)

Results returned by the query on LHS and RHS of Union all operator are

0: jdbc:drill:schema=dfs.tmp> select cast(columns[0] as int) c1 from `testWindow.csv`;
+------+
|  c1  |
+------+
| 100  |
| 10   |
| 2    |
| 50   |
| 55   |
| 67   |
| 113  |
| 119  |
| 89   |
| 57   |
| 61   |
+------+
11 rows selected (0.197 seconds)
0: jdbc:drill:schema=dfs.tmp> select cast(columns[0] as int) c2 from `testWindow.csv`;
+------+
|  c2  |
+------+
| 100  |
| 10   |
| 2    |
| 50   |
| 55   |
| 67   |
| 113  |
| 119  |
| 89   |
| 57   |
| 61   |
+------+
11 rows selected (0.173 seconds)

Note that enclosing the queries within correct parentheses returns correct results. We do not want to return incorrect results to user when the parentheses are missing.

0: jdbc:drill:schema=dfs.tmp> select count(c1) from ((select cast(columns[0] as int) c1 from `testWindow.csv`) union all (select cast(columns[0] as int) c2 from `testWindow.csv`));
+---------+
| EXPR$0  |
+---------+
| 22      |
+---------+
1 row selected (0.234 seconds)