Java tutorial
/* * 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.druid.query.aggregation; import com.fasterxml.jackson.annotation.JsonCreator; import com.fasterxml.jackson.annotation.JsonProperty; import com.google.common.base.Preconditions; import com.google.common.collect.Lists; import org.apache.commons.codec.binary.Base64; import org.apache.druid.java.util.common.StringUtils; import org.apache.druid.segment.ColumnSelectorFactory; import org.apache.druid.segment.ColumnValueSelector; import javax.annotation.Nullable; import java.nio.ByteBuffer; import java.util.Arrays; import java.util.Collections; import java.util.Comparator; import java.util.List; public class HistogramAggregatorFactory extends AggregatorFactory { private final String name; private final String fieldName; private final List<Float> breaksList; private final float[] breaks; @JsonCreator public HistogramAggregatorFactory(@JsonProperty("name") String name, @JsonProperty("fieldName") final String fieldName, @JsonProperty("breaks") final List<Float> breaksList) { Preconditions.checkNotNull(name, "Must have a valid, non-null aggregator name"); Preconditions.checkNotNull(fieldName, "Must have a valid, non-null fieldName"); this.name = name; this.fieldName = fieldName; this.breaksList = (breaksList == null) ? Lists.newArrayList() : breaksList; this.breaks = new float[this.breaksList.size()]; for (int i = 0; i < this.breaksList.size(); ++i) { this.breaks[i] = this.breaksList.get(i); } } @Override public Aggregator factorize(ColumnSelectorFactory metricFactory) { return new HistogramAggregator(metricFactory.makeColumnValueSelector(fieldName), breaks); } @Override public BufferAggregator factorizeBuffered(ColumnSelectorFactory metricFactory) { return new HistogramBufferAggregator(metricFactory.makeColumnValueSelector(fieldName), breaks); } @Override public Comparator getComparator() { return HistogramAggregator.COMPARATOR; } @Override public Object combine(Object lhs, Object rhs) { return HistogramAggregator.combineHistograms(lhs, rhs); } @Override public AggregateCombiner makeAggregateCombiner() { // HistogramAggregatorFactory.combine() delegates to HistogramAggregator.combineHistograms() and it doesn't check // for nulls, so this AggregateCombiner neither. return new ObjectAggregateCombiner<Histogram>() { private Histogram combined; @Override public void reset(ColumnValueSelector selector) { Histogram first = (Histogram) selector.getObject(); if (combined == null) { combined = new Histogram(first); } else { combined.copyFrom(first); } } @Override public void fold(ColumnValueSelector selector) { Histogram other = (Histogram) selector.getObject(); combined.fold(other); } @Override public Class<Histogram> classOfObject() { return Histogram.class; } @Nullable @Override public Histogram getObject() { return combined; } }; } @Override public AggregatorFactory getCombiningFactory() { return new HistogramAggregatorFactory(name, name, breaksList); } @Override public List<AggregatorFactory> getRequiredColumns() { return Collections.singletonList(new HistogramAggregatorFactory(fieldName, fieldName, breaksList)); } @Override public Object deserialize(Object object) { if (object instanceof byte[]) { return Histogram.fromBytes((byte[]) object); } else if (object instanceof ByteBuffer) { return Histogram.fromBytes((ByteBuffer) object); } else if (object instanceof String) { byte[] bytes = Base64.decodeBase64(StringUtils.toUtf8((String) object)); return Histogram.fromBytes(bytes); } return object; } @Override public Object finalizeComputation(Object object) { return ((Histogram) object).asVisual(); } @Override @JsonProperty public String getName() { return name; } @JsonProperty public String getFieldName() { return fieldName; } @JsonProperty public List<Float> getBreaks() { return breaksList; } @Override public List<String> requiredFields() { return Collections.singletonList(fieldName); } @Override public byte[] getCacheKey() { byte[] fieldNameBytes = StringUtils.toUtf8(fieldName); ByteBuffer buf = ByteBuffer.allocate(1 + fieldNameBytes.length + Float.BYTES * breaks.length) .put(AggregatorUtil.HIST_CACHE_TYPE_ID).put(fieldNameBytes).put((byte) 0xFF); buf.asFloatBuffer().put(breaks); return buf.array(); } @Override public String getTypeName() { return "histogram"; } @Override public int getMaxIntermediateSize() { return Long.BYTES * (breaks.length + 1) + Float.BYTES * 2; } @Override public String toString() { return "HistogramAggregatorFactory{" + "name='" + name + '\'' + ", fieldName='" + fieldName + '\'' + ", breaks=" + Arrays.toString(breaks) + '}'; } @Override public boolean equals(Object o) { if (this == o) { return true; } if (o == null || getClass() != o.getClass()) { return false; } HistogramAggregatorFactory that = (HistogramAggregatorFactory) o; if (!Arrays.equals(breaks, that.breaks)) { return false; } if (breaksList != null ? !breaksList.equals(that.breaksList) : that.breaksList != null) { return false; } if (fieldName != null ? !fieldName.equals(that.fieldName) : that.fieldName != null) { return false; } if (name != null ? !name.equals(that.name) : that.name != null) { return false; } return true; } @Override public int hashCode() { int result = name != null ? name.hashCode() : 0; result = 31 * result + (fieldName != null ? fieldName.hashCode() : 0); result = 31 * result + (breaksList != null ? breaksList.hashCode() : 0); result = 31 * result + (breaks != null ? Arrays.hashCode(breaks) : 0); return result; } }