Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/3925#discussion_r116977075
--- Diff:
flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java
---
@@ -1116,13 +1116,27 @@ private void restoreKeyGroupsInStateHandle()
* @throws ClassNotFoundException
* @throws RocksDBException
*/
+ @SuppressWarnings("unchecked")
private void restoreKVStateMetaData() throws IOException,
ClassNotFoundException, RocksDBException {
KeyedBackendSerializationProxy serializationProxy =
new
KeyedBackendSerializationProxy(rocksDBKeyedStateBackend.userCodeClassLoader);
serializationProxy.read(currentStateHandleInView);
+ // check for key serializer compatibility; this also
reconfigures the
+ // key serializer to be compatible, if it is required
and is possible
+ if (StateMigrationUtil.resolveCompatibilityResult(
+ serializationProxy.getKeySerializer(),
+
TypeSerializerSerializationProxy.ClassNotFoundDummyTypeSerializer.class,
+
serializationProxy.getKeySerializerConfigSnapshot(),
+ (TypeSerializer)
rocksDBKeyedStateBackend.keySerializer)
+ .isRequiresMigration()) {
+
+ throw new RuntimeException("The new key
serializer is not compatible to read previous keys. " +
--- End diff --
In the future, we need to be extra careful in this case. If the key's hash
codes change through a state transformation, the their assignment to the
operator instances is broken. Maybe we should already leave a comment about
this here, so that we remember it in the future.
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