[jira] [Created] (KYLIN-4731) Kylin query failing with 'null while executing SQL'

["Mateusz Jerzyk (Jira)" <ji...@apache.org>]

Mateusz Jerzyk created KYLIN-4731:
-------------------------------------

             Summary: Kylin query failing with 'null while executing SQL'
                 Key: KYLIN-4731
                 URL: https://issues.apache.org/jira/browse/KYLIN-4731
             Project: Kylin
          Issue Type: Bug
          Components: Query Engine
    Affects Versions: v3.1.0
            Reporter: Mateusz Jerzyk
         Attachments: error_logs, test_null_date_lookup_cube.json, test_null_date_lookup_model.json

Hello, 

we've recently upgraded Kylin from version 3.0.2 to 3.1.0 and some of the queries that worked well before started returning an error message `null while executing SQL: ...`.

After some investigation, we've found that the problem happens while executing left join on a date column, where the value in the left table is null and it is defined as derived dimension in the cube. 

Here are the steps to reproduce the issue:
 # Creating tables in Hive and filling it with some values

{code:java}
CREATE TABLE `default.test_null_date`
(
    `key1` string,
    `key2` string,
    `date_segment` date,
    `other_date` date
)
STORED AS ORC;

CREATE TABLE `default.test_null_date_lookup`
(
    `date`       date,
    `some_field` string
)
STORED AS ORC;

INSERT INTO TABLE default.test_null_date VALUES
 ('SOMETHING', 'SOMETHING', '2020-01-01', null),
 ('SOMETHING', 'SOMETHING', '2020-01-01', '2020-01-02'),
 ('SOMETHING', 'SOMETHING', '2020-01-01', '2020-01-03');


INSERT INTO TABLE default.test_null_date_lookup VALUES
 ('2020-01-01', 'SOMETHING'),
 ('2020-01-02', 'SOMETHING'),
 ('2020-01-03', 'SOMETHING');
{code}

 # Model definition in Kylin [^test_null_date_lookup_model.json]
 # Cube definition in Kylin [^test_null_date_lookup_cube.json]
 # The example query that fails
{code:java}
SELECT  COUNT(*), "SOME_FIELD"
  FROM  "DEFAULT"."TEST_NULL_DATE"
  LEFT  JOIN  "DEFAULT"."TEST_NULL_DATE_LOOKUP"
    ON  "TEST_NULL_DATE"."OTHER_DATE" = "TEST_NULL_DATE_LOOKUP"."DATE"
 GROUP  BY "SOME_FIELD"{code}

 # Please see also logs of query execution [^error_logs]

 

We think that the issue was introduced here: 
[https://github.com/apache/kylin/commit/6bd5b43bb06b6bf19d1a096d99146396aab8d5b2#diff-fa3dad06dc4edd4d139777c53492c9c2R303]
where the method 
[https://github.com/apache/kylin/blob/kylin-3.1.0/core-common/src/main/java/org/apache/kylin/common/util/DateFormat.java#L158-L168]
is not protected from getting null values and throws NullPointerException



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