/**
* 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 storm.trident.operation.builtin;
import backtype.storm.tuple.Fields;
import java.util.Comparator;
import java.util.PriorityQueue;
import storm.trident.Stream;
import storm.trident.operation.Aggregator;
import storm.trident.operation.Assembly;
import storm.trident.operation.BaseAggregator;
import storm.trident.operation.TridentCollector;
import storm.trident.tuple.TridentTuple;
public class FirstN implements Assembly {
Aggregator _agg;
public FirstN(int n, String sortField) {
this(n, sortField, false);
}
public FirstN(int n, String sortField, boolean reverse) {
if(sortField!=null) {
_agg = new FirstNSortedAgg(n, sortField, reverse);
} else {
_agg = new FirstNAgg(n);
}
}
@Override
public Stream apply(Stream input) {
Fields outputFields = input.getOutputFields();
return input.partitionAggregate(outputFields, _agg, outputFields)
.global()
.partitionAggregate(outputFields, _agg, outputFields);
}
public static class FirstNAgg extends BaseAggregator<FirstNAgg.State> {
int _n;
public FirstNAgg(int n) {
_n = n;
}
static class State {
int emitted = 0;
}
@Override
public State init(Object batchId, TridentCollector collector) {
return new State();
}
@Override
public void aggregate(State val, TridentTuple tuple, TridentCollector collector) {
if(val.emitted < _n) {
collector.emit(tuple);
val.emitted++;
}
}
@Override
public void complete(State val, TridentCollector collector) {
}
}
public static class FirstNSortedAgg extends BaseAggregator<PriorityQueue> {
int _n;
String _sortField;
boolean _reverse;
public FirstNSortedAgg(int n, String sortField, boolean reverse) {
_n = n;
_sortField = sortField;
_reverse = reverse;
}
@Override
public PriorityQueue init(Object batchId, TridentCollector collector) {
return new PriorityQueue(_n, new Comparator<TridentTuple>() {
@Override
public int compare(TridentTuple t1, TridentTuple t2) {
Comparable c1 = (Comparable) t1.getValueByField(_sortField);
Comparable c2 = (Comparable) t2.getValueByField(_sortField);
int ret = c1.compareTo(c2);
if(_reverse) ret *= -1;
return ret;
}
});
}
@Override
public void aggregate(PriorityQueue state, TridentTuple tuple, TridentCollector collector) {
state.add(tuple);
}
@Override
public void complete(PriorityQueue val, TridentCollector collector) {
int total = val.size();
for(int i=0; i<_n && i < total; i++) {
TridentTuple t = (TridentTuple) val.remove();
collector.emit(t);
}
}
}
}