ASF GitHub Bot commented on FLINK-4108:

Github user fhueske commented on the issue:

    Reverting the change and merging

> NPE in Row.productArity
> -----------------------
>                 Key: FLINK-4108
>                 URL: https://issues.apache.org/jira/browse/FLINK-4108
>             Project: Flink
>          Issue Type: Bug
>          Components: Batch Connectors and Input/Output Formats, Type 
> Serialization System
>    Affects Versions: 1.1.0
>            Reporter: Martin Scholl
>            Assignee: Timo Walther
> [this is my first issue request here, please apologize if something is 
> missing]
>  JDBCInputFormat of flink 1.1-SNAPSHOT fails with an NPE in Row.productArity:
> {quote}
> java.io.IOException: Couldn't access resultSet
>         at 
> org.apache.flink.api.java.io.jdbc.JDBCInputFormat.nextRecord(JDBCInputFormat.java:288)
>         at 
> org.apache.flink.api.java.io.jdbc.JDBCInputFormat.nextRecord(JDBCInputFormat.java:98)
>         at 
> org.apache.flink.runtime.operators.DataSourceTask.invoke(DataSourceTask.java:162)
>         at org.apache.flink.runtime.taskmanager.Task.run(Task.java:588)
>         at java.lang.Thread.run(Thread.java:745)
> Caused by: java.lang.NullPointerException
>         at org.apache.flink.api.table.Row.productArity(Row.scala:28)
>         at 
> org.apache.flink.api.java.io.jdbc.JDBCInputFormat.nextRecord(JDBCInputFormat.java:279)
>         ... 4 more
> {quote}
> The code reproduce this can be found in this gist: 
> https://gist.github.com/zeitgeist/b91a60460661618ca4585e082895c616
> The reason for the NPE, I believe, is the way through which Flink creates Row 
> instances through Kryo. As Row expects the number of fields to allocate as a 
> parameter, which Kryo does not provide, the ‘fields’ member of Row ends up 
> being null. As I’m neither a reflection nor a Kryo expert, I rather leave a 
> true analysis to more knowledgable programmers.
> Part of the aforementioned example is a not very elegant workaround though a 
> custom type and a cast (function {{jdbcNoIssue}} + custom Row type {{MyRow}}) 
> to serve as a further hint towards my theory.

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