yhuang-db commented on code in PR #51236: URL: https://github.com/apache/spark/pull/51236#discussion_r2164444948
########## sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/ApproxTopKAggregates.scala: ########## @@ -0,0 +1,290 @@ +/* + * 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.spark.sql.catalyst.expressions.aggregate + +import org.apache.datasketches.common._ +import org.apache.datasketches.frequencies.{ErrorType, ItemsSketch} +import org.apache.datasketches.memory.Memory + +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.analysis.{FunctionRegistry, TypeCheckResult} +import org.apache.spark.sql.catalyst.analysis.TypeCheckResult.{TypeCheckFailure, TypeCheckSuccess} +import org.apache.spark.sql.catalyst.expressions.{ArrayOfDecimalsSerDe, Expression, ExpressionDescription, ImplicitCastInputTypes, Literal} +import org.apache.spark.sql.catalyst.trees.TernaryLike +import org.apache.spark.sql.catalyst.util.{CollationFactory, GenericArrayData} +import org.apache.spark.sql.errors.QueryExecutionErrors +import org.apache.spark.sql.types._ +import org.apache.spark.unsafe.types.UTF8String + +/** + * The ApproxTopK function (i.e., "approx_top_k") is an aggregate function that estimates + * the approximate top K (aka. k-most-frequent) items in a column. + * + * The result is an array of structs, each containing a frequent item and its estimated frequency. + * The items are sorted by their estimated frequency in descending order. + * + * The function uses the ItemsSketch from the DataSketches library to do the estimation. + * + * See [[https://datasketches.apache.org/docs/Frequency/FrequencySketches.html]] + * for more information. + * + * @param first the child expression to estimate the top K items from + * @param second the number of top items to return (K) + * @param third the maximum number of items to track in the sketch + */ +// scalastyle:off line.size.limit +@ExpressionDescription( + usage = + """ + _FUNC_(expr, k, maxItemsTracked) - Returns top k items with their frequency. + `k` An optional INTEGER literal greater than 0. If k is not specified, it defaults to 5. + `maxItemsTracked` An optional INTEGER literal greater than or equal to k. If maxItemsTracked is not specified, it defaults to 10000. + """, + examples = + """ + Examples: + > SELECT approx_top_k(expr, 10, 100) FROM VALUES (0), (1), (1), (2), (2), (2) AS tab(expr); + [{'item':2,'count':3},{'item':1,'count':2},{'item':0,'count':1}] + """, + group = "agg_funcs", + since = "4.1.0") +// scalastyle:on line.size.limit +case class ApproxTopK( + first: Expression, + second: Expression, + third: Expression, + mutableAggBufferOffset: Int = 0, + inputAggBufferOffset: Int = 0) + extends TypedImperativeAggregate[ItemsSketch[Any]] + with ImplicitCastInputTypes + with TernaryLike[Expression] { + + def this(child: Expression, topK: Expression, maxItemsTracked: Expression) = + this(child, topK, maxItemsTracked, 0, 0) + + def this(child: Expression, topK: Int, maxItemsTracked: Int) = + this(child, Literal(topK), Literal(maxItemsTracked), 0, 0) + + def this(child: Expression, topK: Expression) = + this(child, topK, Literal(ApproxTopK.DEFAULT_MAX_ITEMS_TRACKED), 0, 0) + + def this(child: Expression, topK: Int) = + this(child, Literal(topK), Literal(ApproxTopK.DEFAULT_MAX_ITEMS_TRACKED), 0, 0) + + def this(child: Expression) = + this(child, Literal(ApproxTopK.DEFAULT_K), Literal(ApproxTopK.DEFAULT_MAX_ITEMS_TRACKED), 0, 0) + + private lazy val itemDataType: DataType = first.dataType + private lazy val k: Int = { + ApproxTopK.checkExpressionNotNull(second, "k") + val k = second.eval().asInstanceOf[Int] + ApproxTopK.checkK(k) + k + } + private lazy val maxItemsTracked: Int = { + ApproxTopK.checkExpressionNotNull(third, "maxItemsTracked") + val maxItemsTracked = third.eval().asInstanceOf[Int] + ApproxTopK.checkMaxItemsTracked(maxItemsTracked, k) + maxItemsTracked + } + + override def inputTypes: Seq[AbstractDataType] = Seq(AnyDataType, IntegerType, IntegerType) + + override def checkInputDataTypes(): TypeCheckResult = { + val defaultCheck = super.checkInputDataTypes() + if (defaultCheck.isFailure) { + defaultCheck + } else if (!ApproxTopK.checkItemType(itemDataType)) { Review Comment: renamed -- This is an automated message from the Apache Git Service. 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