[FLINK-4108] NPE in Row.productArity

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.1.0
• Fix Version/s: 1.1.4, 1.2.0
• Component/s: API / DataSet, API / Type Serialization System
• Assignee: Timo Walther
• Reporter: Martin Scholl
• Created: 22/Jun/16 22:19
• Updated: 28/Feb/19 13:46
• Resolved: 15/Oct/16 07:54

Description

[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:

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

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.

Issue Links

• links to: GitHub Pull Request #2619