Martin Scholl created FLINK-4108:
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Summary: 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
[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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