Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/6444#discussion_r34105095
--- Diff:
sql/catalyst/src/main/java/org/apache/spark/sql/execution/UnsafeExternalRowSorter.java
---
@@ -0,0 +1,231 @@
+/*
+ * 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.spark.sql.execution;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+import scala.collection.Iterator;
+import scala.math.Ordering;
+
+import com.google.common.annotations.VisibleForTesting;
+
+import org.apache.spark.SparkEnv;
+import org.apache.spark.TaskContext;
+import org.apache.spark.sql.AbstractScalaRowIterator;
+import org.apache.spark.sql.catalyst.InternalRow;
+import org.apache.spark.sql.catalyst.expressions.ObjectUnsafeColumnWriter;
+import org.apache.spark.sql.catalyst.expressions.UnsafeColumnWriter;
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow;
+import org.apache.spark.sql.catalyst.expressions.UnsafeRowConverter;
+import org.apache.spark.sql.catalyst.util.ObjectPool;
+import org.apache.spark.sql.types.StructField;
+import org.apache.spark.sql.types.StructType;
+import org.apache.spark.unsafe.PlatformDependent;
+import org.apache.spark.util.collection.unsafe.sort.PrefixComparator;
+import org.apache.spark.util.collection.unsafe.sort.RecordComparator;
+import org.apache.spark.util.collection.unsafe.sort.UnsafeExternalSorter;
+import org.apache.spark.util.collection.unsafe.sort.UnsafeSorterIterator;
+
+final class UnsafeExternalRowSorter {
+
+ /**
+ * If positive, forces records to be spilled to disk at the given
frequency (measured in numbers
+ * of records). This is only intended to be used in tests.
+ */
+ private int testSpillFrequency = 0;
+
+ private long numRowsInserted = 0;
+
+ private final StructType schema;
+ private final UnsafeRowConverter rowConverter;
+ private final PrefixComputer prefixComputer;
+ private final ObjectPool objPool = new ObjectPool(128);
+ private final UnsafeExternalSorter sorter;
+ private byte[] rowConversionBuffer = new byte[1024 * 8];
+
+ public static abstract class PrefixComputer {
+ abstract long computePrefix(InternalRow row);
+ }
+
+ public UnsafeExternalRowSorter(
+ StructType schema,
+ Ordering<InternalRow> ordering,
+ PrefixComparator prefixComparator,
+ PrefixComputer prefixComputer) throws IOException {
+ this.schema = schema;
+ this.rowConverter = new UnsafeRowConverter(schema);
+ this.prefixComputer = prefixComputer;
+ final SparkEnv sparkEnv = SparkEnv.get();
+ final TaskContext taskContext = TaskContext.get();
+ sorter = new UnsafeExternalSorter(
+ taskContext.taskMemoryManager(),
+ sparkEnv.shuffleMemoryManager(),
+ sparkEnv.blockManager(),
+ taskContext,
+ new RowComparator(ordering, schema.length(), objPool),
+ prefixComparator,
+ 4096,
+ sparkEnv.conf()
+ );
+ }
+
+ /**
+ * Forces spills to occur every `frequency` records. Only for use in
tests.
+ */
+ @VisibleForTesting
+ void setTestSpillFrequency(int frequency) {
+ assert frequency > 0 : "Frequency must be positive";
+ testSpillFrequency = frequency;
+ }
+
+ @VisibleForTesting
+ void insertRow(InternalRow row) throws IOException {
+ final int sizeRequirement = rowConverter.getSizeRequirement(row);
+ if (sizeRequirement > rowConversionBuffer.length) {
+ rowConversionBuffer = new byte[sizeRequirement];
+ } else {
+ // Zero out the buffer that's used to hold the current row. This is
necessary in order
+ // to ensure that rows hash properly, since garbage data from the
previous row could
+ // otherwise end up as padding in this row. As a performance
optimization, we only zero
+ // out the portion of the buffer that we'll actually write to.
+ Arrays.fill(rowConversionBuffer, 0, sizeRequirement, (byte) 0);
+ }
+ final int bytesWritten = rowConverter.writeRow(
+ row, rowConversionBuffer, PlatformDependent.BYTE_ARRAY_OFFSET,
objPool);
+ assert (bytesWritten == sizeRequirement);
+ final long prefix = prefixComputer.computePrefix(row);
+ sorter.insertRecord(
+ rowConversionBuffer,
+ PlatformDependent.BYTE_ARRAY_OFFSET,
+ sizeRequirement,
+ prefix
+ );
+ numRowsInserted++;
+ if (testSpillFrequency > 0 && (numRowsInserted % testSpillFrequency)
== 0) {
+ spill();
+ }
+ }
+
+ @VisibleForTesting
+ void spill() throws IOException {
+ sorter.spill();
+ }
+
+ private void cleanupResources() {
+ sorter.freeMemory();
+ }
+
+ @VisibleForTesting
+ Iterator<InternalRow> sort() throws IOException {
+ try {
+ final UnsafeSorterIterator sortedIterator =
sorter.getSortedIterator();
+ if (!sortedIterator.hasNext()) {
+ // Since we won't ever call next() on an empty iterator, we need
to clean up resources
+ // here in order to prevent memory leaks.
+ cleanupResources();
+ }
+ return new AbstractScalaRowIterator() {
+
+ private final int numFields = schema.length();
+ private final UnsafeRow row = new UnsafeRow();
+
+ @Override
+ public boolean hasNext() {
+ return sortedIterator.hasNext();
+ }
+
+ @Override
+ public InternalRow next() {
+ try {
+ sortedIterator.loadNext();
+ if (hasNext()) {
+ row.pointTo(
+ sortedIterator.getBaseObject(),
sortedIterator.getBaseOffset(), numFields, objPool);
+ return row;
+ } else {
+ final byte[] rowDataCopy = new
byte[sortedIterator.getRecordLength()];
+ PlatformDependent.copyMemory(
+ sortedIterator.getBaseObject(),
+ sortedIterator.getBaseOffset(),
+ rowDataCopy,
+ PlatformDependent.BYTE_ARRAY_OFFSET,
+ sortedIterator.getRecordLength()
+ );
+ row.backingArray = rowDataCopy;
--- End diff --
Do we really need this? row will hold rowDataCopy as `baseObject` anyway.
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