[GitHub] [flink] wsry commented on a change in pull request #13595: [FLINK-19582][network] Introduce sort-merge based blocking shuffle to Flink

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wsry commented on a change in pull request #13595:
URL: https://github.com/apache/flink/pull/13595#discussion_r511591531



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File path: flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/PartitionSortedBuffer.java
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@@ -0,0 +1,390 @@
+/*
+ * 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.io.network.partition;
+
+import org.apache.flink.core.memory.MemorySegment;
+import org.apache.flink.core.memory.MemorySegmentFactory;
+import org.apache.flink.runtime.io.network.buffer.Buffer;
+import org.apache.flink.runtime.io.network.buffer.BufferBuilder;
+import org.apache.flink.runtime.io.network.buffer.BufferPool;
+import org.apache.flink.runtime.io.network.buffer.NetworkBuffer;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+import static org.apache.flink.runtime.io.network.buffer.Buffer.DataType;
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * A {@link SortBuffer} implementation which sorts all appended records only by subpartition index. Records of the
+ * same subpartition keep the appended order.
+ *
+ * <p>It maintains a list of {@link MemorySegment}s as a joint buffer. Data will be appended to the joint buffer
+ * sequentially. When writing a record, an index entry will be appended first. Each index entry has 4 fields: 4
+ * bytes record length, 4 bytes {@link DataType} and 8 bytes address pointing to the next index entry of the same
+ * channel which will be used to index the next record to read when coping data from this {@link SortBuffer}. For
+ * simplicity, no index entry can span multiple segments. The corresponding record data sits right after its index
+ * entry and different from the index entry, records have variable length thus may span multiple segments.
+ */
+@NotThreadSafe
+public class PartitionSortedBuffer implements SortBuffer {
+
+	/**
+	 * Size of an index entry: 4 bytes for record length, 4 bytes for data type and 8 bytes
+	 * for pointer to next entry.
+	 */
+	private static final int INDEX_ENTRY_SIZE = 4 + 4 + 8;

Review comment:
       Good point, I can further optimize it in the future PRs.




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