In fact you can implement own composite data types (like Tuple, Pojo) that
can deal with nullable fields as keys but you need custom serializers and
comparators for that. These types won't be as efficient as types that
cannot handle null fields.
Cheers, Fabian
2015-07-02 20:17 GMT+02:00 Flavio Pompermaier <pomperma...@okkam.it>:
> ok, thanks for the help Stephan!
> On 2 Jul 2015 20:05, "Stephan Ewen" <se...@apache.org> wrote:
>
>> Hi Flavio!
>>
>> Keys cannot be null in Flink, that is a contract deep in the system.
>>
>> Filter out the null valued elements, or, if you want them in the result,
>> I would try to use a special value for "null". That should do it.
>>
>> BTW: In SQL, joining on null usually filters out elements, as key
>> operations on null are undefined.
>>
>> Greetings,
>> Stephan
>>
>>
>> On Thu, Jul 2, 2015 at 7:10 PM, Flavio Pompermaier <pomperma...@okkam.it>
>> wrote:
>>
>>> Hi to all,
>>>
>>> I'd like to join 2 datasets of POJO, let's say for example:
>>>
>>> Person:
>>> - name
>>> - birthPlaceId
>>>
>>> Place:
>>> - id
>>> - name
>>>
>>> I'd like to do
>>> people.coCoGroup(places).where("birthPlaceId").equalTo("id").with(...)
>>>
>>> However, not all people have a birthPlaceId value in my use case..so I
>>> get a NullPointer.
>>> Am I using the wrong operator for this?
>>> This is the stackTrace:
>>>
>>> java.lang.RuntimeException: A NullPointerException occured while
>>> accessing a key field in a POJO. Most likely, the value grouped/joined on
>>> is null. Field name: birthPlaceId
>>> at
>>> org.apache.flink.api.java.typeutils.runtime.PojoComparator.hash(PojoComparator.java:217)
>>> at
>>> org.apache.flink.runtime.operators.shipping.OutputEmitter.hashPartitionDefault(OutputEmitter.java:175)
>>> at
>>> org.apache.flink.runtime.operators.shipping.OutputEmitter.selectChannels(OutputEmitter.java:132)
>>> at
>>> org.apache.flink.runtime.operators.shipping.OutputEmitter.selectChannels(OutputEmitter.java:28)
>>> at
>>> org.apache.flink.runtime.io.network.api.writer.RecordWriter.emit(RecordWriter.java:78)
>>> at
>>> org.apache.flink.runtime.operators.shipping.OutputCollector.collect(OutputCollector.java:65)
>>>
>>> Best,
>>> Flavio
>>>
>>
>>
