/*
* Licensed 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 com.facebook.presto.operator.aggregation;
import com.facebook.presto.spi.block.Block;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.block.BlockCursor;
import com.facebook.presto.operator.GroupByIdBlock;
import com.facebook.presto.spi.type.Type;
import com.google.common.base.Optional;
import com.google.common.primitives.Ints;
import io.airlift.slice.Murmur3;
import io.airlift.slice.SizeOf;
import io.airlift.slice.Slice;
import io.airlift.slice.Slices;
import java.util.ArrayList;
import java.util.List;
import static com.facebook.presto.spi.block.BlockBuilderStatus.DEFAULT_MAX_BLOCK_SIZE_IN_BYTES;
import static com.facebook.presto.spi.type.BigintType.BIGINT;
import static com.facebook.presto.spi.type.DoubleType.DOUBLE;
import static com.facebook.presto.spi.type.VarcharType.VARCHAR;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkState;
public class ApproximateCountDistinctAggregation
extends SimpleAggregationFunction
{
private static final HyperLogLog ESTIMATOR = new HyperLogLog(2048);
// 1 byte for null flag. We use the null flag to propagate a "null" field as intermediate
// and thereby avoid sending a full list of buckets when no value has been added (just an optimization)
private static final int ENTRY_SIZE = SizeOf.SIZE_OF_BYTE + ESTIMATOR.getSizeInBytes();
private static final int SLICE_SIZE = Math.max(ENTRY_SIZE, Ints.checkedCast((DEFAULT_MAX_BLOCK_SIZE_IN_BYTES / ENTRY_SIZE) * ENTRY_SIZE));
private static final int ENTRIES_PER_SLICE = SLICE_SIZE / ENTRY_SIZE;
private final Type parameterType;
public ApproximateCountDistinctAggregation(Type parameterType)
{
super(BIGINT, VARCHAR, parameterType);
checkArgument(parameterType == BIGINT || parameterType == DOUBLE || parameterType == VARCHAR,
"Expected parameter type to be BIGINT, DOUBLE, or VARCHAR, but was %s",
parameterType);
this.parameterType = parameterType;
}
@Override
protected GroupedAccumulator createGroupedAccumulator(Optional<Integer> maskChannel, Optional<Integer> sampleWeightChannel, double confidence, int valueChannel)
{
checkArgument(confidence == 1.0, "approximate count distinct does not support approximate queries");
return new ApproximateCountDistinctGroupedAccumulator(parameterType, valueChannel, maskChannel);
}
public static class ApproximateCountDistinctGroupedAccumulator
extends SimpleGroupedAccumulator
{
private final Type parameterType;
private final List<Slice> slices = new ArrayList<>();
public ApproximateCountDistinctGroupedAccumulator(Type parameterType, int valueChannel, Optional<Integer> maskChannel)
{
super(valueChannel, BIGINT, VARCHAR, maskChannel, Optional.<Integer>absent());
this.parameterType = parameterType;
}
@Override
public long getEstimatedSize()
{
return slices.size() * SLICE_SIZE;
}
@Override
protected void processInput(GroupByIdBlock groupIdsBlock, Block valuesBlock, Optional<Block> maskBlock, Optional<Block> sampleWeightBlock)
{
ensureCapacity(groupIdsBlock.getGroupCount());
BlockCursor values = valuesBlock.cursor();
BlockCursor masks = null;
if (maskBlock.isPresent()) {
masks = maskBlock.get().cursor();
}
for (int position = 0; position < groupIdsBlock.getPositionCount(); position++) {
checkState(values.advanceNextPosition());
checkState(masks == null || masks.advanceNextPosition());
// skip null values
if (!values.isNull() && (masks == null || masks.getBoolean())) {
long groupId = groupIdsBlock.getGroupId(position);
// todo do all of this with shifts and masks
long globalOffset = groupId * ENTRY_SIZE;
int sliceIndex = Ints.checkedCast(globalOffset / SLICE_SIZE);
Slice slice = slices.get(sliceIndex);
int sliceOffset = Ints.checkedCast(globalOffset - (sliceIndex * SLICE_SIZE));
long hash = hash(values, parameterType);
ESTIMATOR.update(hash, slice, sliceOffset + 1);
setNotNull(slice, sliceOffset);
}
}
checkState(!values.advanceNextPosition());
}
@Override
protected void processIntermediate(GroupByIdBlock groupIdsBlock, Block valuesBlock)
{
ensureCapacity(groupIdsBlock.getGroupCount());
BlockCursor intermediates = valuesBlock.cursor();
for (int position = 0; position < groupIdsBlock.getPositionCount(); position++) {
checkState(intermediates.advanceNextPosition());
// skip null values
if (!intermediates.isNull()) {
long groupId = groupIdsBlock.getGroupId(position);
// todo do all of this with shifts and masks
long globalOffset = groupId * ENTRY_SIZE;
int sliceIndex = Ints.checkedCast(globalOffset / SLICE_SIZE);
Slice slice = slices.get(sliceIndex);
int sliceOffset = Ints.checkedCast(globalOffset - (sliceIndex * SLICE_SIZE));
Slice input = intermediates.getSlice();
ESTIMATOR.mergeInto(slice, sliceOffset + 1, input, 0);
setNotNull(slice, sliceOffset);
}
}
checkState(!intermediates.advanceNextPosition());
}
private void ensureCapacity(long groupCount)
{
long neededPages = (groupCount + ENTRIES_PER_SLICE) / ENTRIES_PER_SLICE;
while (slices.size() < neededPages) {
slices.add(Slices.allocate(SLICE_SIZE));
}
}
@Override
public void evaluateIntermediate(int groupId, BlockBuilder output)
{
// todo do all of this with shifts and masks
long globalOffset = groupId * ENTRY_SIZE;
int sliceIndex = Ints.checkedCast(globalOffset / SLICE_SIZE);
Slice valueSlice = slices.get(sliceIndex);
int valueOffset = Ints.checkedCast(globalOffset - (sliceIndex * SLICE_SIZE));
if (isNull(valueSlice, valueOffset)) {
output.appendNull();
}
else {
Slice intermediate = valueSlice.slice(valueOffset + 1, ESTIMATOR.getSizeInBytes());
output.appendSlice(intermediate); // TODO: add BlockBuilder.appendSlice(slice, offset, length) to avoid creating intermediate slice
}
}
@Override
public void evaluateFinal(int groupId, BlockBuilder output)
{
// todo do all of this with shifts and masks
long globalOffset = groupId * ENTRY_SIZE;
int sliceIndex = Ints.checkedCast(globalOffset / SLICE_SIZE);
Slice valueSlice = slices.get(sliceIndex);
int valueOffset = Ints.checkedCast(globalOffset - (sliceIndex * SLICE_SIZE));
if (isNull(valueSlice, valueOffset)) {
output.appendLong(0);
}
else {
output.appendLong(ESTIMATOR.estimate(valueSlice, valueOffset + 1));
}
}
}
@Override
protected Accumulator createAccumulator(Optional<Integer> maskChannel, Optional<Integer> sampleWeightChannel, double confidence, int valueChannel)
{
checkArgument(confidence == 1.0, "approximate count distinct does not support approximate queries");
return new ApproximateCountDistinctAccumulator(parameterType, valueChannel, maskChannel);
}
public static class ApproximateCountDistinctAccumulator
extends SimpleAccumulator
{
private final Type parameterType;
private final Slice slice = Slices.allocate(ENTRY_SIZE);
private boolean notNull;
public ApproximateCountDistinctAccumulator(Type parameterType, int valueChannel, Optional<Integer> maskChannel)
{
super(valueChannel, BIGINT, VARCHAR, maskChannel, Optional.<Integer>absent());
this.parameterType = parameterType;
}
@Override
protected void processInput(Block block, Optional<Block> maskBlock, Optional<Block> sampleWeightBlock)
{
BlockCursor values = block.cursor();
BlockCursor masks = null;
if (maskBlock.isPresent()) {
masks = maskBlock.get().cursor();
}
for (int position = 0; position < block.getPositionCount(); position++) {
checkState(values.advanceNextPosition());
checkState(masks == null || masks.advanceNextPosition());
if (!values.isNull() && (masks == null || masks.getBoolean())) {
notNull = true;
long hash = hash(values, parameterType);
ESTIMATOR.update(hash, slice, 0);
}
}
}
@Override
protected void processIntermediate(Block block)
{
BlockCursor intermediates = block.cursor();
for (int position = 0; position < block.getPositionCount(); position++) {
checkState(intermediates.advanceNextPosition());
if (!intermediates.isNull()) {
notNull = true;
Slice input = intermediates.getSlice();
ESTIMATOR.mergeInto(slice, 0, input, 0);
}
}
}
@Override
public void evaluateIntermediate(BlockBuilder out)
{
if (notNull) {
out.appendSlice(slice);
}
else {
out.appendNull();
}
}
@Override
public void evaluateFinal(BlockBuilder out)
{
if (notNull) {
out.appendLong(ESTIMATOR.estimate(slice, 0));
}
else {
out.appendLong(0);
}
}
}
public static double getStandardError()
{
return ESTIMATOR.getStandardError();
}
private static boolean isNull(Slice valueSlice, int offset)
{
// first byte in value region is null flag
return valueSlice.getByte(offset) == 0;
}
private static void setNotNull(Slice valueSlice, int offset)
{
valueSlice.setByte(offset, 1);
}
private static long hash(BlockCursor values, Type parameterType)
{
if (parameterType == BIGINT) {
long value = values.getLong();
return Murmur3.hash64(value);
}
else if (parameterType == DOUBLE) {
double value = values.getDouble();
return Murmur3.hash64(Double.doubleToLongBits(value));
}
else if (parameterType == VARCHAR) {
return Murmur3.hash64(values.getSlice());
}
else {
throw new IllegalArgumentException("Expected parameter type to be BIGINT, DOUBLE, or VARCHAR");
}
}
}