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https://issues.apache.org/jira/browse/FLINK-8411?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16362843#comment-16362843
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Bowen Li commented on FLINK-8411:
---------------------------------

[~aljoscha] 
For the 1st functionality, isn't [the PR of this 
ticket|https://github.com/apache/flink/pull/5300] merged into 1.5.0 already? If 
not, I think we can just rebase any other changes to it.

For the 2nd functionality, supporting {{null}} doesn't feel right logically... 
with my own experience, allowing null to be added will hide even more user 
bugs. BTW, how to represent {{null}} in RocksDBListState? Is it going to be a 
special char to represent {{null}} in serialization, and handle it specially in 
deserialization?

Please feel free to implement it yourself to save time from back-and-forth 
communication and code review.

> HeapListState#add(null) will wipe out entire list state
> -------------------------------------------------------
>
>                 Key: FLINK-8411
>                 URL: https://issues.apache.org/jira/browse/FLINK-8411
>             Project: Flink
>          Issue Type: Improvement
>          Components: State Backends, Checkpointing
>    Affects Versions: 1.4.0
>            Reporter: Bowen Li
>            Assignee: Bowen Li
>            Priority: Blocker
>             Fix For: 1.5.0
>
>
> You can see that {{HeapListState#add(null)}} will result in the whole state 
> being cleared or wiped out. There's never a unit test for {{List#add(null)}} 
> in {{StateBackendTestBase}}
> {code:java}
> // HeapListState
> @Override
>       public void add(V value) {
>               final N namespace = currentNamespace;
>               if (value == null) {
>                       clear();
>                       return;
>               }
>               final StateTable<K, N, ArrayList<V>> map = stateTable;
>               ArrayList<V> list = map.get(namespace);
>               if (list == null) {
>                       list = new ArrayList<>();
>                       map.put(namespace, list);
>               }
>               list.add(value);
>       }
> {code}
> {code:java}
> // RocksDBListState
> @Override
>       public void add(V value) throws IOException {
>               try {
>                       writeCurrentKeyWithGroupAndNamespace();
>                       byte[] key = keySerializationStream.toByteArray();
>                       keySerializationStream.reset();
>                       DataOutputViewStreamWrapper out = new 
> DataOutputViewStreamWrapper(keySerializationStream);
>                       valueSerializer.serialize(value, out);
>                       backend.db.merge(columnFamily, writeOptions, key, 
> keySerializationStream.toByteArray());
>               } catch (Exception e) {
>                       throw new RuntimeException("Error while adding data to 
> RocksDB", e);
>               }
>       }
> {code}
> The fix should correct the behavior to be consistent between the two state 
> backends, as well as adding a unit test for {{ListState#add(null)}}. For the 
> correct behavior, I believe adding null with {{add(null)}} should simply be 
> ignored without any consequences.
> cc [~srichter]



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