Fu Kai created FLINK-23740:
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Summary: SQL Full Outer Join bug
Key: FLINK-23740
URL: https://issues.apache.org/jira/browse/FLINK-23740
Project: Flink
Issue Type: Bug
Components: Table SQL / Runtime
Affects Versions: 1.13.2, 1.13.1
Reporter: Fu Kai
Hi team,
We encountered an issue about FULL OUTER JOIN of Flink SQL, which happens
occasionally at very low probability that join output records can be cannot be
correctly updated. We cannot locate the issue for now by glancing at the code
of
[StreamingJoinOperator.|https://github.com/apache/flink/blob/master/flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/operators/join/stream/StreamingJoinOperator.java#L198]
It cannot be stably reproduced and it happens with massive data volume.
The reason we suspect it's the FULL OUER join problem instead of others like
LEFT OUTER join is because the issue only arises after we introduced FULL OUTER
into the join flow. The query we are using is like the following. The are two
join code pieces, the fist one contains solely left join(though with nested)
and there is no issue detected; the second one contains both left and full
outer join, and the problem is that sometimes update from the left table A(and
other tables before the full outer join operator) cannot be reflected in the
final output. We suspect it could be the introduce of full outer join caused
the problem though at a very low probability(~10 out of 30million).
The bug also could be something else, the FULL OUT join issue is just based on
our current experiment and observation.
{code:java}
create table A(
k1 int,
k2 int,
k3 int,
k4 int,
k5 int,
PRIMARY KEY (k1, k2, k3, k4, k5) NOT ENFORCED
) WITH ();create table B(
k1 int,
k2 int,
k3 int,
PRIMARY KEY (k1, k2, k3) NOT ENFORCED
) WITH ();create table C(
k1 int,
k2 int,
k3 int,
PRIMARY KEY (k1, k2, k3) NOT ENFORCED
) WITH ();create table D(
k1 int,
k2 int,
PRIMARY KEY (k1, k2) NOT ENFORCED
) WITH ();
// query with left join, no issue detected
select * from A
left outer join
(select * from B
left outer join C
on
B.k1 = C.k1
B.k2 = C.k2
B.k3 = C.k3
) as BC
on
A.k1 = BC.k1
A.k2 = BC.k2
A.k3 = BC.k3
left outer join D
on
A.k1 = D.k1
A.k2 = D.k2
;
// query with full outer join combined with left outer join, record updates
from left table A cannot be updated in the final output record some times
select * from A
left outer join
(select * from B
full outer join C
on
B.k1 = C.k1
B.k2 = C.k2
B.k3 = C.k3
) as BC
on
A.k1 = BC.k1
A.k2 = BC.k2
A.k3 = BC.k3
left outer join D
on
A.k1 = D.k1
A.k2 = D.k2
;
{code}
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