jon-wei commented on a change in pull request #6581: Moments Sketch custom aggregator URL: https://github.com/apache/incubator-druid/pull/6581#discussion_r252842035
########## File path: extensions-contrib/momentsketch/src/main/java/org/apache/druid/query/aggregation/momentsketch/aggregator/MomentSketchAggregatorFactory.java ########## @@ -0,0 +1,295 @@ +/* + * 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.momentsketch.aggregator; + +import com.fasterxml.jackson.annotation.JsonCreator; +import com.fasterxml.jackson.annotation.JsonProperty; +import org.apache.commons.codec.Charsets; +import org.apache.commons.codec.binary.Base64; +import org.apache.druid.java.util.common.ISE; +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.momentsketch.MomentSketchWrapper; +import org.apache.druid.query.cache.CacheKeyBuilder; +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 javax.annotation.Nullable; +import java.util.Collections; +import java.util.Comparator; +import java.util.List; +import java.util.Objects; + +/** + * Aggregation operations over the moment-based quantile sketch + * available on <a href="https://github.com/stanford-futuredata/momentsketch";>github</a> and described + * in the paper <a href="https://arxiv.org/abs/1803.01969";>Moment-based quantile sketches</a>. + * + * This sketch stores a set of (k) statistics about univariate metrics that can be used to + * solve for approximate quantiles of the original distribution at query time after aggregating + * the statistics. + */ +public class MomentSketchAggregatorFactory extends AggregatorFactory +{ + // Default number of moments (k) chosen for ~1% quantile error. + public static final int DEFAULT_K = 13; + // Safer to compress data with unknown ranges by default, but reduces accuracy on uniform data + public static final boolean DEFAULT_COMPRESS = true; + + private final String name; + private final String fieldName; + // Number of moments tracked. Larger k allows for better estimates but greater resource usage + private final int k; + // Controls whether or not data is compressed onto a smaller range using arcsinh + private final boolean compress; + private final byte cacheTypeId; + + public static final String TYPE_NAME = "momentSketch"; + + @JsonCreator + public MomentSketchAggregatorFactory( + @JsonProperty("name") final String name, + @JsonProperty("fieldName") final String fieldName, + @Nullable @JsonProperty("k") final Integer k, + @Nullable @JsonProperty("compress") final Boolean compress + ) + { + this(name, fieldName, k, compress, AggregatorUtil.MOMENTS_SKETCH_BUILD_CACHE_TYPE_ID); + } + + MomentSketchAggregatorFactory( + final String name, + final String fieldName, + @Nullable final Integer k, + @Nullable final Boolean compress, + final byte cacheTypeId + ) + { + Objects.requireNonNull(name, "Must have a valid, non-null aggregator name"); + this.name = name; + Objects.requireNonNull(fieldName, "Parameter fieldName must be specified"); + this.fieldName = fieldName; + this.k = k == null ? DEFAULT_K : k; + this.compress = compress == null ? DEFAULT_COMPRESS : compress; + this.cacheTypeId = cacheTypeId; + } + + + @Override + public byte[] getCacheKey() + { + return new CacheKeyBuilder( + cacheTypeId + ).appendString(fieldName).appendInt(k).appendBoolean(compress).build(); + } + + + @Override + public Aggregator factorize(ColumnSelectorFactory metricFactory) + { + ColumnCapabilities cap = metricFactory.getColumnCapabilities(fieldName); + if (cap == null || ValueType.isNumeric(cap.getType())) { + final ColumnValueSelector<Double> selector = metricFactory.makeColumnValueSelector(fieldName); + return new MomentSketchBuildAggregator(selector, k, getCompress()); + } else { + final ColumnValueSelector<MomentSketchWrapper> selector = metricFactory.makeColumnValueSelector(fieldName); + return new MomentSketchMergeAggregator(selector, k, getCompress()); + } + } + + @Override + public BufferAggregator factorizeBuffered(ColumnSelectorFactory metricFactory) + { + ColumnCapabilities cap = metricFactory.getColumnCapabilities(fieldName); + if (cap == null || ValueType.isNumeric(cap.getType())) { + final ColumnValueSelector<Double> selector = metricFactory.makeColumnValueSelector(fieldName); + return new MomentSketchBuildBufferAggregator(selector, k, getCompress()); + } else { + final ColumnValueSelector<MomentSketchWrapper> selector = metricFactory.makeColumnValueSelector(fieldName); + return new MomentSketchMergeBufferAggregator(selector, k, getCompress()); + } + } + + public static final Comparator<MomentSketchWrapper> COMPARATOR = Comparator.nullsFirst( + Comparator.comparingDouble(a -> a.getPowerSums()[0]) + ); + + @Override + public Comparator getComparator() + { + return COMPARATOR; + } + + @Override + public Object combine(@Nullable Object lhs, @Nullable Object rhs) + { + if (lhs == null) { + return rhs; + } + if (rhs == null) { + return lhs; + } + MomentSketchWrapper union = (MomentSketchWrapper) lhs; + union.merge((MomentSketchWrapper) rhs); + return union; + } + + @Override + public AggregatorFactory getCombiningFactory() + { + return new MomentSketchMergeAggregatorFactory(name, k, compress); + } + + @Override + public AggregatorFactory getMergingFactory(AggregatorFactory other) throws AggregatorFactoryNotMergeableException + { + if (other.getName().equals(this.getName()) && this.getClass() == other.getClass()) { + return getCombiningFactory(); + } else { + throw new AggregatorFactoryNotMergeableException(this, other); + } + } + + @Override + public List<AggregatorFactory> getRequiredColumns() + { + return Collections.singletonList( + new MomentSketchAggregatorFactory( + fieldName, + fieldName, + k, + compress + ) + ); + } + + private MomentSketchWrapper deserializeFromByteArray(byte[] bytes) + { + return MomentSketchWrapper.fromByteArray(bytes); + } + + @Override + public Object deserialize(Object serializedSketch) + { + if (serializedSketch instanceof String) { + String str = (String) serializedSketch; + return deserializeFromByteArray(Base64.decodeBase64(str.getBytes(Charsets.UTF_8))); Review comment: This should use `StringUtils.decodeBase64` and `StringUtils.toUtf8` to pass the style checks ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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