[GitHub] [flink] aljoscha commented on a change in pull request #14782: [FLINK-21167] Make StateTable snapshots iterable

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aljoscha commented on a change in pull request #14782:
URL: https://github.com/apache/flink/pull/14782#discussion_r566205955



##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/IterableStateSnapshot.java
##########
@@ -0,0 +1,32 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.runtime.state;
+
+import org.apache.flink.annotation.Internal;
+
+import java.util.Iterator;
+
+/**
+ * A {@link StateSnapshot} that can be represented and thus iterated over {@link StateEntry
+ * StateEntries}.

Review comment:
       ```suggestion
    * A {@link StateSnapshot} that can return an iterator over all contained {@link StateEntry
    * StateEntries}.
   ```

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/heap/CopyOnWriteStateMapSnapshot.java
##########
@@ -110,6 +110,19 @@ int getSnapshotVersion() {
         return snapshotVersion;
     }
 
+    @Override
+    public SnapshotIterator<K, N, S> getIterator(

Review comment:
       That was easy... 😅

##########
File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/heap/NestedStateMapSnapshot.java
##########
@@ -48,6 +53,35 @@ public NestedStateMapSnapshot(NestedStateMap<K, N, S> owningStateMap) {
         super(owningStateMap);
     }
 
+    @Override
+    public Iterator<StateEntry<K, N, S>> getIterator(
+            @Nonnull TypeSerializer<K> keySerializer,
+            @Nonnull TypeSerializer<N> namespaceSerializer,
+            @Nonnull TypeSerializer<S> stateSerializer,
+            @Nullable StateSnapshotTransformer<S> stateSnapshotTransformer) {
+        if (stateSnapshotTransformer == null) {
+            return owningStateMap.iterator();
+        } else {
+            return StreamSupport.stream(
+                            Spliterators.spliteratorUnknownSize(owningStateMap.iterator(), 0),
+                            false)
+                    .map(entry -> transformEntry(stateSnapshotTransformer, entry))
+                    .filter(Objects::nonNull)
+                    .iterator();
+        }
+    }
+
+    private StateEntry<K, N, S> transformEntry(
+            StateSnapshotTransformer<S> stateSnapshotTransformer, StateEntry<K, N, S> entry) {
+        S transformedState = stateSnapshotTransformer.filterOrTransform(entry.getState());
+        if (transformedState != null) {
+            return new StateEntry.SimpleStateEntry<>(

Review comment:
       It seems a bit icky that we hardcode `SimpleStateEntry` here. Maybe adding a `StateEntry.filterOrTransform(StateSnapshotTransformer)` that returns a new `StateEntry` could do the trick?




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