RyanBerti commented on code in PR #40615: URL: https://github.com/apache/spark/pull/40615#discussion_r1181937235
########## sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/datasketchesAggregates.scala: ########## @@ -0,0 +1,368 @@ +/* + * 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.SketchesArgumentException +import org.apache.datasketches.hll.{HllSketch, Union} +import org.apache.datasketches.memory.Memory + +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.expressions.{ExpectsInputTypes, Expression, ExpressionDescription, Literal} +import org.apache.spark.sql.catalyst.trees.BinaryLike +import org.apache.spark.sql.types.{AbstractDataType, BinaryType, BooleanType, DataType, IntegerType, LongType, StringType, TypeCollection} +import org.apache.spark.unsafe.types.UTF8String + + +/** + * The HllSketchAgg function utilizes a Datasketches HllSketch instance to + * probabilistically count the number of unique values in a given column, and + * outputs the binary representation of the HllSketch. + * + * See [[https://datasketches.apache.org/docs/HLL/HLL.html]] for more information + * + * @param child child expression against which unique counting will occur + * @param lgConfigK the log-base-2 of K, where K is the number of buckets or slots for the sketch + */ +// scalastyle:off line.size.limit +@ExpressionDescription( + usage = """ + _FUNC_(expr, lgConfigK) - Returns the HllSketch's updateable binary representation. + `lgConfigK` (optional) the log-base-2 of K, with K is the number of buckets or + slots for the HllSketch. """, + examples = """ + Examples: + > SELECT hll_sketch_estimate(_FUNC_(col, 12)) FROM VALUES (1), (1), (2), (2), (3) tab(col); + 3 + """, + group = "agg_funcs", + since = "3.5.0") +// scalastyle:on line.size.limit +case class HllSketchAgg( + child: Expression, + lgConfigKExpression: Expression, + mutableAggBufferOffset: Int = 0, + inputAggBufferOffset: Int = 0) + extends TypedImperativeAggregate[HllSketch] with BinaryLike[Expression] with ExpectsInputTypes { + + // Hllsketch config - mark as lazy so that they're not evaluated during tree transformation. + + lazy val lgConfigK: Int = { + val lgConfigK = lgConfigKExpression.eval().asInstanceOf[Int] + // can't use HllUtil.checkLgK so replicate the check + if (lgConfigK < 4 || lgConfigK > 21) { + throw new SketchesArgumentException("Invalid lgConfigK value") + } else { + lgConfigK + } + } + + // Constructors + + def this(child: Expression) = { + this(child, Literal(HllSketch.DEFAULT_LG_K), 0, 0) + } + + def this(child: Expression, lgConfigK: Expression) = { + this(child, lgConfigK, 0, 0) + } + + def this(child: Expression, lgConfigK: Int) = { + this(child, Literal(lgConfigK), 0, 0) + } + + // Copy constructors required by ImperativeAggregate + + override def withNewMutableAggBufferOffset(newMutableAggBufferOffset: Int): HllSketchAgg = + copy(mutableAggBufferOffset = newMutableAggBufferOffset) + + override def withNewInputAggBufferOffset(newInputAggBufferOffset: Int): HllSketchAgg = + copy(inputAggBufferOffset = newInputAggBufferOffset) + + override protected def withNewChildrenInternal(newLeft: Expression, + newRight: Expression): HllSketchAgg = + copy(child = newLeft, lgConfigKExpression = newRight) + + // Overrides for TernaryLike + + override def left: Expression = child + + override def right: Expression = lgConfigKExpression + + // Overrides for TypedImperativeAggregate + + override def prettyName: String = "hll_sketch_agg" + + override def inputTypes: Seq[AbstractDataType] = + Seq(TypeCollection(IntegerType, LongType, StringType, BinaryType), IntegerType) + + override def dataType: DataType = BinaryType + + override def nullable: Boolean = false + + /** + * Instantiate an HllSketch instance using the lgConfigK param. + * + * @return an HllSketch instance + */ + override def createAggregationBuffer(): HllSketch = { + new HllSketch(lgConfigK) + } + + /** + * Evaluate the input row and update the HllSketch instance with the row's value. + * The update function only supports a subset of Spark SQL types, and an + * UnsupportedOperationException will be thrown for unsupported types. + * + * @param sketch The HllSketch instance. + * @param input an input row Review Comment: Updated arg references + descriptions. -- This is an automated message from the Apache Git Service. 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