chenboat commented on code in PR #11098: URL: https://github.com/apache/pinot/pull/11098#discussion_r1281307520
########## pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/FrequentLongsSketchAggregationFunction.java: ########## @@ -0,0 +1,251 @@ +/** + * 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.pinot.core.query.aggregation.function; + +import com.google.common.base.Preconditions; +import java.util.List; +import java.util.Map; +import org.apache.datasketches.frequencies.LongsSketch; +import org.apache.datasketches.memory.Memory; +import org.apache.pinot.common.request.context.ExpressionContext; +import org.apache.pinot.common.utils.DataSchema; +import org.apache.pinot.core.common.BlockValSet; +import org.apache.pinot.core.query.aggregation.AggregationResultHolder; +import org.apache.pinot.core.query.aggregation.ObjectAggregationResultHolder; +import org.apache.pinot.core.query.aggregation.groupby.GroupByResultHolder; +import org.apache.pinot.core.query.aggregation.groupby.ObjectGroupByResultHolder; +import org.apache.pinot.segment.local.customobject.SerializedFrequentLongsSketch; +import org.apache.pinot.segment.spi.AggregationFunctionType; +import org.apache.pinot.spi.data.FieldSpec; + + +/** + * <p> + * {@code FrequentLongsSketchAggregationFunction} provides an approximate FrequentItems aggregation function based on + * <a href="https://datasketches.apache.org/docs/Frequency/FrequentItemsOverview.html";>Apache DataSketches library</a>. + * It is memory efficient compared to exact counting. + * </p> + * <p> + * The function takes an INT or LONG column as input and returns a Base64 encoded sketch object which can be + * deserialized and used to estimate the frequency of items in the dataset (how many times they appear). + * </p> + * <p><b>FREQUENT_STRINGS_SKETCH(col, maxMapSize=256)</b></p> + * <p>E.g.:</p> + * <ul> + * <li><b>FREQUENT_LONGS_SKETCH(col)</b></li> + * <li><b>FREQUENT_LONGS_SKETCH(col, 1024)</b></li> + * </ul> + * + * <p> + * If the column type is BYTES, the aggregation function will assume it is a serialized FrequentItems data sketch + * of type `LongsSketch`and will attempt to deserialize it for merging with other sketch objects. + * </p> + * + * <p> + * There is a variation of the function (<b>FREQUENT_STRINGS_SKETCH</b>) which accepts STRING type input columns. + * </p> + */ +public class FrequentLongsSketchAggregationFunction + extends BaseSingleInputAggregationFunction<LongsSketch, Comparable<?>> { + protected static final int DEFAULT_MAX_MAP_SIZE = 256; + + protected int _maxMapSize; + + public FrequentLongsSketchAggregationFunction(List<ExpressionContext> arguments) { + super(arguments.get(0)); + int numArguments = arguments.size(); + Preconditions.checkArgument(numArguments == 1 || numArguments == 2, + "Expecting 1 or 2 arguments for FrequentLongsSketch function: FREQUENTITEMSSKETCH(column, maxMapSize"); + _maxMapSize = numArguments == 2 ? arguments.get(1).getLiteral().getIntValue() : DEFAULT_MAX_MAP_SIZE; + } + + @Override + public AggregationFunctionType getType() { + return AggregationFunctionType.FREQUENTLONGSSKETCH; + } + + @Override + public AggregationResultHolder createAggregationResultHolder() { + return new ObjectAggregationResultHolder(); + } + + @Override + public GroupByResultHolder createGroupByResultHolder(int initialCapacity, int maxCapacity) { + return new ObjectGroupByResultHolder(initialCapacity, maxCapacity); + } + + @Override + public void aggregate(int length, AggregationResultHolder aggregationResultHolder, + Map<ExpressionContext, BlockValSet> blockValSetMap) { + BlockValSet valueSet = blockValSetMap.get(_expression); + FieldSpec.DataType valueType = valueSet.getValueType(); + + LongsSketch sketch = getOrCreateSketch(aggregationResultHolder); + + if (valueType == FieldSpec.DataType.BYTES) { Review Comment: NIT: can we use switch-case here? -- This is an automated message from the Apache Git Service. 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