[GitHub] [iceberg] openinx commented on a change in pull request #1145: Implement the flink stream writer to accept the row data and emit the complete data files event to downstream

[GitBox <gi...@apache.org>]

openinx commented on a change in pull request #1145:
URL: https://github.com/apache/iceberg/pull/1145#discussion_r448709770



##########
File path: core/src/main/java/org/apache/iceberg/BaseFile.java
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@@ -360,7 +360,7 @@ public ByteBuffer keyMetadata() {
     if (list != null) {
       List<E> copy = Lists.newArrayListWithExpectedSize(list.size());
       copy.addAll(list);
-      return Collections.unmodifiableList(copy);

Review comment:
       Because flink is depending on the `com.esotericsoftware.kryo.serializers` to serialize & deserialize the class/object, it will fill few `null` value into the fields which is a collection data type. the code is here: https://github.com/EsotericSoftware/kryo/blob/46ef9788fa1d3fb020ce6e8f33f431c9fb54cb35/src/com/esotericsoftware/kryo/serializers/CollectionSerializer.java#L102. 
   
   And if we don't make it modifiable, then it will throw the stacktrace : 
   
   ```
   java.lang.UnsupportedOperationException
   Serialization trace:
   splitOffsets (org.apache.iceberg.GenericDataFile)
   com.esotericsoftware.kryo.KryoException: java.lang.UnsupportedOperationException
   Serialization trace:
   splitOffsets (org.apache.iceberg.GenericDataFile)
   	at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:125)
   	at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:528)
   	at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:657)
   	at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.copy(KryoSerializer.java:262)
   	at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.copy(PojoSerializer.java:239)
   	at org.apache.flink.streaming.util.AbstractStreamOperatorTestHarness$MockOutput.collect(AbstractStreamOperatorTestHarness.java:693)
   	at org.apache.flink.streaming.util.AbstractStreamOperatorTestHarness$MockOutput.collect(AbstractStreamOperatorTestHarness.java:661)
   	at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:730)
   	at org.apache.flink.streaming.api.operators.AbstractStreamOperator$CountingOutput.collect(AbstractStreamOperator.java:708)
   	at org.apache.iceberg.flink.IcebergStreamWriter.emit(IcebergStreamWriter.java:149)
   	at org.apache.iceberg.flink.IcebergStreamWriter.prepareSnapshotPreBarrier(IcebergStreamWriter.java:119)
   	at org.apache.flink.streaming.util.AbstractStreamOperatorTestHarness.prepareSnapshotPreBarrier(AbstractStreamOperatorTestHarness.java:565)
   	at org.apache.iceberg.flink.TestIcebergStreamWriter.testWritingTable(TestIcebergStreamWriter.java:101)
   Caused by: java.lang.UnsupportedOperationException
   	at java.util.Collections$UnmodifiableCollection.add(Collections.java:1057)
   	at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:109)
   	at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:22)
   	at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:679)
   	at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:106)
   	... 70 more
   ```




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