jihoonson commented on a change in pull request #7331: TDigest backed sketch aggregators URL: https://github.com/apache/incubator-druid/pull/7331#discussion_r279134453
########## File path: extensions-contrib/tdigestsketch/src/main/java/org/apache/druid/query/aggregation/tdigestsketch/TDigestBuildSketchAggregatorFactory.java ########## @@ -0,0 +1,269 @@ +/* + * 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.tdigestsketch; + +import com.fasterxml.jackson.annotation.JsonCreator; +import com.fasterxml.jackson.annotation.JsonProperty; +import com.tdunning.math.stats.MergingDigest; +import com.tdunning.math.stats.TDigest; +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.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.Nonnull; +import javax.annotation.Nullable; +import java.util.Collections; +import java.util.Comparator; +import java.util.List; +import java.util.Objects; + +/** + * Aggregation operations over the tdigest-based quantile sketch + * available on <a href="https://github.com/tdunning/t-digest";>github</a> and described + * in the paper + * <a href="https://github.com/tdunning/t-digest/blob/master/docs/t-digest-paper/histo.pdf";> + * Computing extremely accurate quantiles using t-digests</a>. + * <p> + * <p> + * At the time of writing this implementation, there are two flavors of {@link TDigest} + * available - {@link MergingDigest} and {@link com.tdunning.math.stats.AVLTreeDigest}. + * This implementation uses {@link MergingDigest} since it is more suited for the cases + * when we have to merge intermediate aggregations which Druid needs to do as + * part of query processing. + */ +public class TDigestBuildSketchAggregatorFactory extends AggregatorFactory +{ + + // Default compression + public static final int DEFAULT_COMRESSION = 100; + + @Nonnull + private final String name; + @Nonnull + private final String fieldName; + @Nonnull + final Integer compression; + @Nonnull + private final byte cacheTypeId; + + public static final String TYPE_NAME = "buildTDigestSketch"; + + @JsonCreator + public TDigestBuildSketchAggregatorFactory( + @JsonProperty("name") final String name, + @JsonProperty("fieldName") final String fieldName, + @Nullable @JsonProperty("compression") final Integer compression + ) + { + this(name, fieldName, compression, AggregatorUtil.TDIGEST_BUILD_SKETCH_CACHE_TYPE_ID); + } + + TDigestBuildSketchAggregatorFactory( + final String name, + final String fieldName, + @Nullable final Integer compression, + 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.compression = compression == null ? DEFAULT_COMRESSION : compression; + this.cacheTypeId = cacheTypeId; + } + + + @Override + public byte[] getCacheKey() + { + return new CacheKeyBuilder( + cacheTypeId + ).appendString(fieldName).appendInt(compression).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 TDigestBuildSketchAggregator(selector, compression); + } else { + final ColumnValueSelector<MergingDigest> selector = metricFactory.makeColumnValueSelector(fieldName); + return new TDigestMergeSketchAggregator(selector, compression); + } + } + + @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 TDigestBuildSketchBufferAggregator(selector, compression); + } else { + final ColumnValueSelector<MergingDigest> selector = metricFactory.makeColumnValueSelector(fieldName); + return new TDigestMergeSketchBufferAggregator(selector, compression); + } + } + + public static final Comparator<TDigest> COMPARATOR = Comparator.nullsFirst( + Comparator.comparingLong(a -> a.size()) + ); + + @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; + } + TDigest union = (TDigest) lhs; + union.add((TDigest) rhs); + return union; + } + + @Override + public AggregatorFactory getCombiningFactory() + { + return new TDigestMergeSketchAggregatorFactory(name, name, compression); + } + + @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 TDigestBuildSketchAggregatorFactory( + fieldName, + fieldName, + compression + ) + ); + } + + @Override + public Object deserialize(Object serializedSketch) + { + return TDigestSketchOperations.deserialize(serializedSketch); + } + + @Override + public Object finalizeComputation(Object object) + { + return object; + } + + @Override + @JsonProperty + public String getName() + { + return name; + } + + @JsonProperty + public String getFieldName() + { + return fieldName; + } + + @JsonProperty + public int getCompression() + { + return compression; + } + + @Override + public List<String> requiredFields() + { + return Collections.singletonList(fieldName); + } + + @Override + public String getTypeName() + { + return TYPE_NAME; + } + + @Override + public int getMaxIntermediateSize() + { + //TODO: samarth need to come up with a good value here Review comment: Would you please raise an issue for this? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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