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https://issues.apache.org/jira/browse/SPARK-22552?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen reassigned SPARK-22552:
---------------------------------

         Assignee:     (was: Shixiong Zhu)
         Priority: Minor  (was: Major)
    Fix Version/s:     (was: 2.2.2)
                       (was: 2.3.0)

> Cannot Union multiple kafka streams
> -----------------------------------
>
>                 Key: SPARK-22552
>                 URL: https://issues.apache.org/jira/browse/SPARK-22552
>             Project: Spark
>          Issue Type: Bug
>          Components: Structured Streaming
>    Affects Versions: 2.2.0
>            Reporter: sachin malhotra
>            Priority: Minor
>
> When unioning multiple kafka streams I learned that the resulting dataframe 
> only contains the data that exists in the dataframe that initiated the union 
> i.e. if df1.union(df2) (or a chaining of unions) the result will only contain 
> the rows that exist in df1.
> Now to be more specific this occurs when data comes in during the same 
> micro-batch for all three streams. If you wait for each single row to be 
> processed for each stream the union does return the right results. 
> For example, if you have 3 kafka streams and you:
> send message 1 to stream 1, WAIT for batch to finish, send message 2 to 
> stream 2, wait for batch to finish, send message 3 to stream 3, wait for 
> batch to finish. Union will return the right data.
> But if you,
> send message 1,2,3, WAIT for batch to finish, you only receive data in the 
> first stream when unioning all three dataframes



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