HyukjinKwon commented on code in PR #38375: URL: https://github.com/apache/spark/pull/38375#discussion_r1003159352
########## sql/core/src/main/scala/org/apache/spark/sql/execution/stat/FrequentItems.scala: ########## @@ -85,42 +51,142 @@ object FrequentItems extends Logging { cols: Seq[String], support: Double): DataFrame = { require(support >= 1e-4 && support <= 1.0, s"Support must be in [1e-4, 1], but got $support.") - val numCols = cols.length + // number of max items to keep counts for val sizeOfMap = (1 / support).toInt - val countMaps = Seq.tabulate(numCols)(i => new FreqItemCounter(sizeOfMap)) - - val freqItems = df.select(cols.map(Column(_)) : _*).rdd.treeAggregate(countMaps)( - seqOp = (counts, row) => { - var i = 0 - while (i < numCols) { - val thisMap = counts(i) - val key = row.get(i) - thisMap.add(key, 1L) - i += 1 - } - counts - }, - combOp = (baseCounts, counts) => { - var i = 0 - while (i < numCols) { - baseCounts(i).merge(counts(i)) - i += 1 + + val frequentItemCols = cols.map { col => + val aggExpr = new CollectFrequentItems(functions.col(col).expr, sizeOfMap) + Column(aggExpr.toAggregateExpression(isDistinct = false)).as(s"${col}_freqItems") + } + + df.select(frequentItemCols: _*) + } +} + +case class CollectFrequentItems( + child: Expression, + size: Int, + mutableAggBufferOffset: Int = 0, + inputAggBufferOffset: Int = 0) extends TypedImperativeAggregate[mutable.Map[Any, Long]] + with ImplicitCastInputTypes with UnaryLike[Expression] { + require(size > 0) + + def this(child: Expression, size: Int) = this(child, size, 0, 0) + + // Returns empty array for empty inputs + override def nullable: Boolean = false + + override def dataType: DataType = ArrayType(child.dataType, containsNull = child.nullable) + + override def inputTypes: Seq[AbstractDataType] = Seq(AnyDataType) + + override def prettyName: String = "collect_frequent_items" + + override def createAggregationBuffer(): mutable.Map[Any, Long] = + mutable.Map.empty[Any, Long] + + private def add(map: mutable.Map[Any, Long], key: Any, count: Long): mutable.Map[Any, Long] = { + if (map.contains(key)) { + map(key) += count + } else { + if (map.size < size) { + map += key -> count + } else { + val minCount = if (map.values.isEmpty) 0 else map.values.min + val remainder = count - minCount + if (remainder >= 0) { + map += key -> count // something will get kicked out, so we can add this + map.retain((k, v) => v > minCount) + map.transform((k, v) => v - minCount) + } else { + map.transform((k, v) => v - count) } - baseCounts } - ) - val justItems = freqItems.map(m => m.baseMap.keys.toArray) - val resultRow = Row(justItems : _*) + } + map + } + + override def update( + buffer: mutable.Map[Any, Long], + input: InternalRow): mutable.Map[Any, Long] = { + val key = child.eval(input) + if (key != null) { + this.add(buffer, InternalRow.copyValue(key), 1L) + } else { + this.add(buffer, key, 1L) + } + } + + override def merge( + buffer: mutable.Map[Any, Long], + input: mutable.Map[Any, Long]): mutable.Map[Any, Long] = { + input.foreach { case (k, v) => Review Comment: If this is a hot path, you can just use a plan `for` loop or `while.` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org