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/*
* 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 org.apache.spark.SparkEnv;
import org.apache.spark.TaskContext;
import org.apache.spark.internal.config.package$;
import org.apache.spark.sql.catalyst.InternalRow;
import org.apache.spark.sql.catalyst.expressions.UnsafeProjection;
import org.apache.spark.sql.catalyst.expressions.UnsafeRow;
import org.apache.spark.sql.catalyst.plans.logical.Aggregate$;
import org.apache.spark.sql.types.StructType;
import org.apache.spark.unsafe.KVIterator;
import org.apache.spark.unsafe.Platform;
import org.apache.spark.unsafe.map.BytesToBytesMap;
/**
* Unsafe-based HashMap for performing aggregations where the aggregated values are fixed-width.
*
* This map supports a maximum of 2 billion keys.
*/
public final class UnsafeFixedWidthAggregationMap {
/**
* An empty aggregation buffer, encoded in UnsafeRow format. When inserting a new key into the
* map, we copy this buffer and use it as the value.
*/
private final byte[] emptyAggregationBuffer;
private final StructType aggregationBufferSchema;
private final StructType groupingKeySchema;
/**
* Encodes grouping keys as UnsafeRows.
*/
private final UnsafeProjection groupingKeyProjection;
/**
* A hashmap which maps from opaque bytearray keys to bytearray values.
*/
private final BytesToBytesMap map;
/**
* Re-used pointer to the current aggregation buffer
*/
private final UnsafeRow currentAggregationBuffer;
/**
* @return true if UnsafeFixedWidthAggregationMap supports aggregation buffers with the given
* schema, false otherwise.
*/
public static boolean supportsAggregationBufferSchema(StructType schema) {
return Aggregate$.MODULE$.isAggregateBufferMutable(schema);
}
/**
* Create a new UnsafeFixedWidthAggregationMap.
*
* @param emptyAggregationBuffer the default value for new keys (a "zero" of the agg. function)
* @param aggregationBufferSchema the schema of the aggregation buffer, used for row conversion.
* @param groupingKeySchema the schema of the grouping key, used for row conversion.
* @param taskContext the current task context.
* @param initialCapacity the initial capacity of the map (a sizing hint to avoid re-hashing).
* @param pageSizeBytes the data page size, in bytes; limits the maximum record size.
*/
public UnsafeFixedWidthAggregationMap(
InternalRow emptyAggregationBuffer,
StructType aggregationBufferSchema,
StructType groupingKeySchema,
TaskContext taskContext,
int initialCapacity,
long pageSizeBytes) {
this.aggregationBufferSchema = aggregationBufferSchema;
this.currentAggregationBuffer = new UnsafeRow(aggregationBufferSchema.length());
this.groupingKeyProjection = UnsafeProjection.create(groupingKeySchema);
this.groupingKeySchema = groupingKeySchema;
this.map = new BytesToBytesMap(
taskContext.taskMemoryManager(), initialCapacity, pageSizeBytes);
// Initialize the buffer for aggregation value
final UnsafeProjection valueProjection = UnsafeProjection.create(aggregationBufferSchema);
this.emptyAggregationBuffer = valueProjection.apply(emptyAggregationBuffer).getBytes();
// Register a cleanup task with TaskContext to ensure that memory is guaranteed to be freed at
// the end of the task. This is necessary to avoid memory leaks in when the downstream operator
// does not fully consume the aggregation map's output (e.g. aggregate followed by limit).
taskContext.addTaskCompletionListener(context -> {
free();
});
}
/**
* Return the aggregation buffer for the current group. For efficiency, all calls to this method
* return the same object. If additional memory could not be allocated, then this method will
* signal an error by returning null.
*/
public UnsafeRow getAggregationBuffer(InternalRow groupingKey) {
final UnsafeRow unsafeGroupingKeyRow = this.groupingKeyProjection.apply(groupingKey);
return getAggregationBufferFromUnsafeRow(unsafeGroupingKeyRow);
}
public UnsafeRow getAggregationBufferFromUnsafeRow(UnsafeRow key) {
return getAggregationBufferFromUnsafeRow(key, key.hashCode());
}
public UnsafeRow getAggregationBufferFromUnsafeRow(UnsafeRow key, int hash) {
// Probe our map using the serialized key
final BytesToBytesMap.Location loc = map.lookup(
key.getBaseObject(),
key.getBaseOffset(),
key.getSizeInBytes(),
hash);
if (!loc.isDefined()) {
// This is the first time that we've seen this grouping key, so we'll insert a copy of the
// empty aggregation buffer into the map:
boolean putSucceeded = loc.append(
key.getBaseObject(),
key.getBaseOffset(),
key.getSizeInBytes(),
emptyAggregationBuffer,
Platform.BYTE_ARRAY_OFFSET,
emptyAggregationBuffer.length
);
if (!putSucceeded) {
return null;
}
}
// Reset the pointer to point to the value that we just stored or looked up:
currentAggregationBuffer.pointTo(
loc.getValueBase(),
loc.getValueOffset(),
loc.getValueLength()
);
return currentAggregationBuffer;
}
/**
* Returns an iterator over the keys and values in this map. This uses destructive iterator of
* BytesToBytesMap. So it is illegal to call any other method on this map after `iterator()` has
* been called.
*
* For efficiency, each call returns the same object.
*/
public KVIterator iterator() {
return new KVIterator() {
private final BytesToBytesMap.MapIterator mapLocationIterator =
map.destructiveIterator();
private final UnsafeRow key = new UnsafeRow(groupingKeySchema.length());
private final UnsafeRow value = new UnsafeRow(aggregationBufferSchema.length());
@Override
public boolean next() {
if (mapLocationIterator.hasNext()) {
final BytesToBytesMap.Location loc = mapLocationIterator.next();
key.pointTo(
loc.getKeyBase(),
loc.getKeyOffset(),
loc.getKeyLength()
);
value.pointTo(
loc.getValueBase(),
loc.getValueOffset(),
loc.getValueLength()
);
return true;
} else {
return false;
}
}
@Override
public UnsafeRow getKey() {
return key;
}
@Override
public UnsafeRow getValue() {
return value;
}
@Override
public void close() {
// Do nothing.
}
};
}
/**
* Return the peak memory used so far, in bytes.
*/
public long getPeakMemoryUsedBytes() {
return map.getPeakMemoryUsedBytes();
}
/**
* Free the memory associated with this map. This is idempotent and can be called multiple times.
*/
public void free() {
map.free();
}
/**
* Gets the average number of hash probes per key lookup in the underlying `BytesToBytesMap`.
*/
public double getAvgHashProbesPerKey() {
return map.getAvgHashProbesPerKey();
}
/**
* Sorts the map's records in place, spill them to disk, and returns an [[UnsafeKVExternalSorter]]
*
* Note that the map will be reset for inserting new records, and the returned sorter can NOT be
* used to insert records.
*/
public UnsafeKVExternalSorter destructAndCreateExternalSorter() throws IOException {
return new UnsafeKVExternalSorter(
groupingKeySchema,
aggregationBufferSchema,
SparkEnv.get().blockManager(),
SparkEnv.get().serializerManager(),
map.getPageSizeBytes(),
(int) SparkEnv.get().conf().get(
package$.MODULE$.SHUFFLE_SPILL_NUM_ELEMENTS_FORCE_SPILL_THRESHOLD()),
map);
}
}
