FengZhou created IMPALA-13428:
---------------------------------
Summary: Using a left join with a window function results in
incorrect outcomes.
Key: IMPALA-13428
URL: https://issues.apache.org/jira/browse/IMPALA-13428
Project: IMPALA
Issue Type: Bug
Components: Backend
Affects Versions: Impala 4.1.2
Reporter: FengZhou
When using a window function, and performing a left join, filtering based on
the field used by the window function, inconsistencies can occur during the
pushdown process.
{code:java}
create table if not exists test.a(
a string
, b string
);
insert into test.a
values ('a', '1')
, ('b', '2')
;
create table if not exists test.b(
a string
, b string
, c string
);
insert into test.b
values ('a', '1', '1')
, ('b', '2', '2')
, ('c', '3', '3')
, ('c', '3', '4')
, ('c', '3', '5')
;
select *
from (SELECT
t2.b
FROM test.a t1
LEFT JOIN (SELECT a
, ROW_NUMBER() OVER(PARTITION BY a ORDER BY b) b
-- , count(1) b
FROM test.b) T2
ON t1.a=t2.a
) t
where b = 10{code}
The correct result should have no records at all. However, in version 4.1.2,
the result that was executed contains 4 records with *NULL* values.
Here is the execution plan.
{code:java}
PLAN-ROOT SINK
|
09:EXCHANGE [UNPARTITIONED]
|
05:HASH JOIN [RIGHT OUTER JOIN, PARTITIONED]
| hash predicates: a = t1.a
| row-size=44B cardinality=224
|
|--08:EXCHANGE [HASH(t1.a)]
| |
| 00:SCAN HDFS [test.a t1]
| HDFS partitions=1/1 files=2 size=1.06KB
| row-size=12B cardinality=224
|
04:SELECT
| predicates: row_number() = 10 <---- There seems to be a problem here.
| row-size=32B cardinality=218
|
03:ANALYTIC
| functions: row_number()
| partition by: a
| order by: b ASC
| window: ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
| row-size=32B cardinality=218
|
07:TOP-N
| partition by: a
| order by: b ASC
| partition limit: 10
| row-size=24B cardinality=218
|
06:EXCHANGE [HASH(a)]
|
02:TOP-N
| partition by: a
| order by: b ASC
| partition limit: 10
| source expr: row_number() = CAST(10 AS BIGINT)
| row-size=24B cardinality=218
|
01:SCAN HDFS [test.b]
HDFS partitions=1/1 files=2 size=1.54KB
row-size=24B cardinality=218{code}
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