[IMPALA-4479] Evaluation of a constant boolean expr results in a NULL instead of FALSE.

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: Impala 2.8.0
• Fix Version/s: Impala 2.8.0
• Component/s: Frontend
• Labels: correctness
• Target Version: Impala 2.8.0
• Assignee: Alexander Behm
• Reporter: Alexander Behm
• Created: 12/Nov/16 05:31
• Updated: 15/Nov/16 15:38
• Resolved: 15/Nov/16 15:38

Description

When folding constant expressions Impala may incorrectly replace a constant boolean expression with NULL instead of FALSE. This may lead to incorrect results.

Repro:

explain select * from functional_kudu.alltypes
where bool_col = (true and false);

+------------------------------------------------------------------------------------+
| Explain String                                                                     |
+------------------------------------------------------------------------------------+
| Estimated Per-Host Requirements: Memory=0B VCores=1                                |
| WARNING: The following tables are missing relevant table and/or column statistics. |
| functional_kudu.alltypes                                                           |
|                                                                                    |
| PLAN-ROOT SINK                                                                     |
| |                                                                                  |
| 01:EXCHANGE [UNPARTITIONED]                                                        |
| |                                                                                  |
| 00:SCAN KUDU [functional_kudu.alltypes]                                            |
|    predicates: bool_col = NULL      <--- Should be FALSE                                               |
+------------------------------------------------------------------------------------+

The underlying issue is a simple one. We are not calling the correct isSet() function on a thrift struct. See LiteralExpr.create():

...
case BOOLEAN:
  if (val.isBool_val()) result = new BoolLiteral(val.bool_val);
  break;
...

The check should be: val.isSetBool_val()