org.apache.flink.api.java.functions.FirstReducer Maven / Gradle / Ivy
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* 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
*
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* distributed under the License is distributed on an "AS IS" BASIS,
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*/
package org.apache.flink.api.java.functions;
import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.functions.GroupCombineFunction;
import org.apache.flink.api.common.functions.GroupReduceFunction;
import org.apache.flink.util.Collector;
/**
* Reducer that only emits the first N elements in a group.
*
* @param
*/
@Internal
public class FirstReducer implements GroupReduceFunction, GroupCombineFunction {
private static final long serialVersionUID = 1L;
private final int count;
public FirstReducer(int n) {
this.count = n;
}
@Override
public void reduce(Iterable values, Collector out) throws Exception {
int emitCnt = 0;
for (T val : values) {
out.collect(val);
emitCnt++;
if (emitCnt == count) {
break;
}
}
}
@Override
public void combine(Iterable values, Collector out) throws Exception {
reduce(values, out);
}
}