[IMPALA-765] Incorrect results when changing the order of aggregates in the select list with codegen enabled

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 1.2.3
• Fix Version/s: Impala 1.3
• Labels: impala
• Assignee: Nong Li
• Reporter: Srinath
• Created: 23/Jan/14 23:04
• Updated: 10/Mar/14 22:27
• Resolved: 10/Mar/14 22:27

Description

With codegen enabled, correct results are observed for the following query
(The type of tinyint_col is tinyint).

Query: select sum(tinyint_col * tinyint_col) , count(tinyint_col) from alltypesagg
+--------------------------------+--------------------+
| sum(tinyint_col * tinyint_col) | count(tinyint_col) |
+--------------------------------+--------------------+
| 285000                         | 9000               |
+--------------------------------+--------------------+

However, the sum is calculated incorrectly when the select list is flipped:

Query: select count(tinyint_col), sum(tinyint_col * tinyint_col) from alltypesagg
+--------------------+--------------------------------+
| count(tinyint_col) | sum(tinyint_col * tinyint_col) |
+--------------------+--------------------------------+
| 9000               | 0                              |
+--------------------+--------------------------------+

The same problem occurs when a column of type smallint is used,
but NOT when columns of type int or bigint are used.

With disable_codegen set to true, correct results are observed in both cases.