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https://issues.apache.org/jira/browse/FLINK-6034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15940131#comment-15940131
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ASF GitHub Bot commented on FLINK-6034:
---------------------------------------
Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/3531#discussion_r107874660
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/KeyedStateHandle.java
---
@@ -0,0 +1,40 @@
+/*
+ * 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;
+
+/**
+ * Base for the handles of the checkpointed states in keyed streams. When
+ * recovering from failures, the handle will be passed to all tasks whose
key
+ * group ranges overlap with it.
+ */
+public interface KeyedStateHandle extends StateObject {
+
+ /**
+ * Returns the range of the key groups contained in the state.
+ */
+ KeyGroupRange getKeyGroupRange();
+
+ /**
+ * Returns a keyed state handle which contains the states for the given
--- End diff --
This comment is not correct. It does not necessarily contain the whole
given range, but the intersection of the given range with the range of the
handle. You can just copy-paste it from the method in `KeyGroupsStateHandle`.
> Add KeyedStateHandle for the snapshots in keyed streams
> -------------------------------------------------------
>
> Key: FLINK-6034
> URL: https://issues.apache.org/jira/browse/FLINK-6034
> Project: Flink
> Issue Type: Sub-task
> Components: State Backends, Checkpointing
> Reporter: Xiaogang Shi
> Assignee: Xiaogang Shi
>
> Currently, the only type of the snapshots in keyed streams is
> {{KeyGroupsStateHandle}} which is full and store the states one group after
> another. With the introduction of incremental checkpointing, we need a higher
> level abstraction of keyed snapshots to allow flexible snapshot formats.
> The implementation of {{KeyedStateHandle}} s may vary a lot in different
> backends. The only information needed in {{KeyedStateHandle}} s is their key
> group range. When recovering the job with a different degree of parallelism,
> {{KeyedStateHandle}} s will be assigned to those subtasks whose key group
> ranges overlap with their ranges.
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