[jira] [Created] (FLINK-23740) SQL Full Outer Join bug

["Fu Kai (Jira)" <ji...@apache.org>]

Fu Kai created FLINK-23740:
------------------------------

             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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