extensions-core/histogram/src/main/java/org/apache/druid/query/aggregation/histogram/ApproximateHistogramAggregatorFactory.java

/*
 * 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.histogram;


import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonTypeName;
import com.google.common.base.Preconditions;
import org.apache.druid.java.util.common.StringUtils;
import org.apache.druid.query.aggregation.AggregateCombiner;
import org.apache.druid.query.aggregation.Aggregator;
import org.apache.druid.query.aggregation.AggregatorFactory;
import org.apache.druid.query.aggregation.AggregatorFactoryNotMergeableException;
import org.apache.druid.query.aggregation.AggregatorUtil;
import org.apache.druid.query.aggregation.BufferAggregator;
import org.apache.druid.query.aggregation.ObjectAggregateCombiner;
import org.apache.druid.query.aggregation.VectorAggregator;
import org.apache.druid.query.cache.CacheKeyBuilder;
import org.apache.druid.segment.ColumnInspector;
import org.apache.druid.segment.ColumnSelectorFactory;
import org.apache.druid.segment.ColumnValueSelector;
import org.apache.druid.segment.column.ColumnCapabilities;
import org.apache.druid.segment.column.ValueType;
import org.apache.druid.segment.vector.VectorColumnSelectorFactory;

import javax.annotation.Nullable;
import java.nio.ByteBuffer;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;

@JsonTypeName("approxHistogram")
public class ApproximateHistogramAggregatorFactory extends AggregatorFactory
{
  protected final String name;
  protected final String fieldName;

  protected final int resolution;
  protected final int numBuckets;

  protected final float lowerLimit;
  protected final float upperLimit;

  protected final boolean finalizeAsBase64Binary;

  @JsonCreator
  public ApproximateHistogramAggregatorFactory(
      @JsonProperty("name") String name,
      @JsonProperty("fieldName") String fieldName,
      @JsonProperty("resolution") Integer resolution,
      @JsonProperty("numBuckets") Integer numBuckets,
      @JsonProperty("lowerLimit") Float lowerLimit,
      @JsonProperty("upperLimit") Float upperLimit,
      @JsonProperty("finalizeAsBase64Binary") @Nullable Boolean finalizeAsBase64Binary

  )
  {
    this.name = name;
    this.fieldName = fieldName;
    this.resolution = resolution == null ? ApproximateHistogram.DEFAULT_HISTOGRAM_SIZE : resolution;
    this.numBuckets = numBuckets == null ? ApproximateHistogram.DEFAULT_BUCKET_SIZE : numBuckets;
    this.lowerLimit = lowerLimit == null ? Float.NEGATIVE_INFINITY : lowerLimit;
    this.upperLimit = upperLimit == null ? Float.POSITIVE_INFINITY : upperLimit;
    this.finalizeAsBase64Binary = finalizeAsBase64Binary == null ? false : finalizeAsBase64Binary;

    Preconditions.checkArgument(this.resolution > 0, "resolution must be greater than 1");
    Preconditions.checkArgument(this.numBuckets > 0, "numBuckets must be greater than 1");
    Preconditions.checkArgument(this.upperLimit > this.lowerLimit, "upperLimit must be greater than lowerLimit");
  }

  @Override
  public Aggregator factorize(ColumnSelectorFactory metricFactory)
  {
    return new ApproximateHistogramAggregator(
        metricFactory.makeColumnValueSelector(fieldName),
        resolution,
        lowerLimit,
        upperLimit
    );
  }

  @Override
  public BufferAggregator factorizeBuffered(ColumnSelectorFactory metricFactory)
  {
    return new ApproximateHistogramBufferAggregator(
        metricFactory.makeColumnValueSelector(fieldName),
        resolution
    );
  }

  @Override
  public VectorAggregator factorizeVector(VectorColumnSelectorFactory metricVectorFactory)
  {
    return new ApproximateHistogramVectorAggregator(
        metricVectorFactory.makeValueSelector(fieldName),
        resolution
    );
  }

  @Override
  public boolean canVectorize(ColumnInspector columnInspector)
  {
    /* skip vectorization for string types which may be parseable to numbers. There is no vector equivalent of
     string value selector*/
    ColumnCapabilities capabilities = columnInspector.getColumnCapabilities(fieldName);
    return (capabilities != null) && capabilities.getType().isNumeric();
  }

  @Override
  public Comparator getComparator()
  {
    return ApproximateHistogramAggregator.COMPARATOR;
  }

  @Override
  public Object combine(Object lhs, Object rhs)
  {
    return ApproximateHistogramAggregator.combineHistograms(lhs, rhs);
  }

  @Override
  public AggregateCombiner makeAggregateCombiner()
  {
    // ApproximateHistogramAggregatorFactory.combine() delegates to ApproximateHistogramAggregator.combineHistograms()
    // and it doesn't check for nulls, so this AggregateCombiner neither.
    return new ObjectAggregateCombiner<ApproximateHistogram>()
    {
      private final ApproximateHistogram combined = new ApproximateHistogram();

      @Override
      public void reset(ColumnValueSelector selector)
      {
        ApproximateHistogram first = (ApproximateHistogram) selector.getObject();
        combined.copy(first);
      }

      @Override
      public void fold(ColumnValueSelector selector)
      {
        ApproximateHistogram other = (ApproximateHistogram) selector.getObject();
        combined.foldFast(other);
      }

      @Override
      public Class<ApproximateHistogram> classOfObject()
      {
        return ApproximateHistogram.class;
      }

      @Nullable
      @Override
      public ApproximateHistogram getObject()
      {
        return combined;
      }
    };
  }

  @Override
  public AggregatorFactory getCombiningFactory()
  {
    return new ApproximateHistogramFoldingAggregatorFactory(
        name,
        name,
        resolution,
        numBuckets,
        lowerLimit,
        upperLimit,
        finalizeAsBase64Binary
    );
  }

  @Override
  public AggregatorFactory getMergingFactory(AggregatorFactory other) throws AggregatorFactoryNotMergeableException
  {
    if (other.getName().equals(this.getName()) && other instanceof ApproximateHistogramAggregatorFactory) {
      ApproximateHistogramAggregatorFactory castedOther = (ApproximateHistogramAggregatorFactory) other;

      return new ApproximateHistogramFoldingAggregatorFactory(
          name,
          name,
          Math.max(resolution, castedOther.resolution),
          numBuckets,
          Math.min(lowerLimit, castedOther.lowerLimit),
          Math.max(upperLimit, castedOther.upperLimit),
          finalizeAsBase64Binary
      );

    } else {
      throw new AggregatorFactoryNotMergeableException(this, other);
    }
  }

  @Override
  public List<AggregatorFactory> getRequiredColumns()
  {
    return Collections.singletonList(
        new ApproximateHistogramAggregatorFactory(
            fieldName,
            fieldName,
            resolution,
            numBuckets,
            lowerLimit,
            upperLimit,
            finalizeAsBase64Binary
        )
    );
  }

  @Override
  public Object deserialize(Object object)
  {
    if (object instanceof byte[]) {
      final ApproximateHistogram ah = ApproximateHistogram.fromBytes((byte[]) object);
      ah.setLowerLimit(lowerLimit);
      ah.setUpperLimit(upperLimit);

      return ah;
    } else if (object instanceof ByteBuffer) {
      final ApproximateHistogram ah = ApproximateHistogram.fromBytes((ByteBuffer) object);
      ah.setLowerLimit(lowerLimit);
      ah.setUpperLimit(upperLimit);

      return ah;
    } else if (object instanceof String) {
      byte[] bytes = StringUtils.decodeBase64(StringUtils.toUtf8((String) object));
      final ApproximateHistogram ah = ApproximateHistogram.fromBytes(bytes);
      ah.setLowerLimit(lowerLimit);
      ah.setUpperLimit(upperLimit);

      return ah;
    } else {
      return object;
    }
  }

  @Nullable
  @Override
  public Object finalizeComputation(@Nullable Object object)
  {
    if (finalizeAsBase64Binary) {
      return object;
    } else {
      return object == null ? null : ((ApproximateHistogram) object).toHistogram(numBuckets);
    }
  }

  @JsonProperty
  @Override
  public String getName()
  {
    return name;
  }

  @JsonProperty
  public String getFieldName()
  {
    return fieldName;
  }

  @JsonProperty
  public int getResolution()
  {
    return resolution;
  }

  @JsonProperty
  public float getLowerLimit()
  {
    return lowerLimit;
  }

  @JsonProperty
  public float getUpperLimit()
  {
    return upperLimit;
  }

  @JsonProperty
  public int getNumBuckets()
  {
    return numBuckets;
  }

  @Override
  public List<String> requiredFields()
  {
    return Collections.singletonList(fieldName);
  }

  @Override
  public byte[] getCacheKey()
  {
    CacheKeyBuilder builder = new CacheKeyBuilder(AggregatorUtil.APPROX_HIST_CACHE_TYPE_ID)
        .appendString(fieldName)
        .appendInt(resolution)
        .appendInt(numBuckets)
        .appendFloat(lowerLimit)
        .appendFloat(upperLimit)
        .appendBoolean(finalizeAsBase64Binary);

    return builder.build();
  }

  @Override
  public String getComplexTypeName()
  {
    return "approximateHistogram";
  }

  /**
   * actual type is {@link ApproximateHistogram}
   */
  @Override
  public ValueType getType()
  {
    return ValueType.COMPLEX;
  }

  /**
   * actual type is {@link ApproximateHistogram} if {@link #finalizeAsBase64Binary} is set, else {@link Histogram}
   */
  @Override
  public ValueType getFinalizedType()
  {
    return ValueType.COMPLEX;
  }

  @Override
  public int getMaxIntermediateSize()
  {
    return new ApproximateHistogram(resolution).getMaxStorageSize();
  }

  @Override
  public String toString()
  {
    return "ApproximateHistogramAggregatorFactory{" +
           "name='" + name + '\'' +
           ", fieldName='" + fieldName + '\'' +
           ", resolution=" + resolution +
           ", numBuckets=" + numBuckets +
           ", lowerLimit=" + lowerLimit +
           ", upperLimit=" + upperLimit +
           ", finalizeAsBase64Binary=" + finalizeAsBase64Binary +
           '}';
  }

  @Override
  public boolean equals(Object o)
  {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    ApproximateHistogramAggregatorFactory that = (ApproximateHistogramAggregatorFactory) o;
    return resolution == that.resolution &&
           numBuckets == that.numBuckets &&
           Float.compare(that.lowerLimit, lowerLimit) == 0 &&
           Float.compare(that.upperLimit, upperLimit) == 0 &&
           finalizeAsBase64Binary == that.finalizeAsBase64Binary &&
           Objects.equals(name, that.name) &&
           Objects.equals(fieldName, that.fieldName);
  }

  @Override
  public int hashCode()
  {
    return Objects.hash(name, fieldName, resolution, numBuckets, lowerLimit, upperLimit, finalizeAsBase64Binary);
  }
}