[IMPALA-3125] Incorrect assignment of outer join On-clause that only references one side of the join.

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Impala 2.3.0, Impala 2.5.0
• Fix Version/s: Impala 2.8.0
• Component/s: Frontend
• Labels: correctness downgraded
• Target Version: Impala 2.8.0
• Assignee: Alexander Behm
• Reporter: Alexander Behm
• Created: 03/Mar/16 00:53
• Updated: 05/Dec/16 18:28
• Resolved: 05/Dec/16 18:28

Description

Impala may return incorrect results for queries that have an outer join with an On-clause predicate that references at least two tables, but not the right-hand side of the join.

Example query to repro and its plan:

select a.id aid, b.id bid, a.int_col aint, b.int_col bint
from functional.alltypes a
inner join functional.alltypes b
  on a.int_col = b.int_col
left outer join functional.alltypes c
  on a.id = b.id and b.bigint_col = c.bigint_col

+-----------------------------------------------------------+
| Explain String                                            |
+-----------------------------------------------------------+
| Estimated Per-Host Requirements: Memory=320.08MB VCores=3 |
|                                                           |
| 08:EXCHANGE [UNPARTITIONED]                               |
| |                                                         |
| 04:HASH JOIN [LEFT OUTER JOIN, BROADCAST]                 |
| |  hash predicates: b.bigint_col = c.bigint_col         <---  b.id = a.id should be here and not in join below|
| |                                                         |
| |--07:EXCHANGE [BROADCAST]                                |
| |  |                                                      |
| |  02:SCAN HDFS [functional.alltypes c]                   |
| |     partitions=24/24 files=24 size=478.45KB             |
| |                                                         |
| 03:HASH JOIN [INNER JOIN, PARTITIONED]                    |
| |  hash predicates: b.int_col = a.int_col, b.id = a.id    |
| |  runtime filters: RF000 <- a.int_col, RF001 <- a.id     |
| |                                                         |
| |--06:EXCHANGE [HASH(a.int_col,a.id)]                     |
| |  |                                                      |
| |  00:SCAN HDFS [functional.alltypes a]                   |
| |     partitions=24/24 files=24 size=478.45KB             |
| |                                                         |
| 05:EXCHANGE [HASH(b.int_col,b.id)]                        |
| |                                                         |
| 01:SCAN HDFS [functional.alltypes b]                      |
|    partitions=24/24 files=24 size=478.45KB                |
|    runtime filters: RF000 -> b.int_col, RF001 -> b.id     |
+-----------------------------------------------------------+