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From "Andras Istvan Nagy (Jira)" <j...@apache.org>
Subject [jira] [Created] (KYLIN-4246) Wrong results from real-time streaming when an optional field is used as a dimension
Date Mon, 11 Nov 2019 13:06:00 GMT
Andras Istvan Nagy created KYLIN-4246:
-----------------------------------------

             Summary: Wrong results from real-time streaming when an optional field is used
as a dimension
                 Key: KYLIN-4246
                 URL: https://issues.apache.org/jira/browse/KYLIN-4246
             Project: Kylin
          Issue Type: Bug
          Components: Real-time Streaming
    Affects Versions: v3.0.0-alpha
            Reporter: Andras Istvan Nagy


We run into an issue which seems to be related to the real-time streaming receiver.

We have an optional field in the kafka messages, that is, in some cases it has a value, in
other cases it is missing from the JSON message. This field is defined as a dimension and
is used in the queries. We were assuming that when this field is missing from the JSON message,
its value will be interpreted as null (as is the case with the Kylin batch engine).

The results for queries that include this field are correct for those segments that have been
rebuilt with the Kylin batch engine, but incorrect when they are built by the streaming receiver.

E.g. in the example query below (simplified version of our actual queries), optional_field
is an optional field, and mandatory_field always has a value. In our case, the below query
should produce 0 as output, because we have no such records where optional_field has a value
(is not null), and mandatory_field='X'. Still, for those segments that are coming from the
streaming receiver, we get non-0 values.

{{select count(*)}}
{{from movement_events}}
{{where mandatory_field='X'}}
{{and optional_field is not null;}}

Is this a known issue? Can we avoid this somehow, without changing the source events?

 



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