/*
* 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.operator.aggregation.state.AccumulatorStateSerializer;
import com.facebook.presto.operator.aggregation.state.HyperLogLogState;
import com.facebook.presto.operator.aggregation.state.StateCompiler;
import com.facebook.presto.spi.block.BlockBuilder;
import com.facebook.presto.spi.type.HyperLogLogType;
import com.facebook.presto.type.SqlType;
import io.airlift.slice.Slice;
import io.airlift.stats.cardinality.HyperLogLog;
@AggregationFunction("merge")
public final class MergeHyperLogLogAggregation
{
private static final AccumulatorStateSerializer<HyperLogLogState> serializer = new StateCompiler().generateStateSerializer(HyperLogLogState.class);
private MergeHyperLogLogAggregation() {}
@InputFunction
@IntermediateInputFunction
public static void merge(HyperLogLogState state, @SqlType(HyperLogLogType.class) Slice value)
{
HyperLogLog input = HyperLogLog.newInstance(value);
HyperLogLog previous = state.getHyperLogLog();
if (previous == null) {
state.setHyperLogLog(input);
state.addMemoryUsage(input.estimatedInMemorySize());
}
else {
state.addMemoryUsage(-previous.estimatedInMemorySize());
previous.mergeWith(input);
state.addMemoryUsage(previous.estimatedInMemorySize());
}
}
@OutputFunction(HyperLogLogType.class)
public static void output(HyperLogLogState state, BlockBuilder out)
{
serializer.serialize(state, out);
}
}