diff options
5 files changed, 256 insertions, 5 deletions
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala index 2669300029..7be2a01da1 100644 --- a/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala +++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala @@ -331,6 +331,17 @@ class DataFrame private[sql]( def na: DataFrameNaFunctions = new DataFrameNaFunctions(this) /** + * Returns a [[DataFrameStatFunctions]] for working statistic functions support. + * {{{ + * // Finding frequent items in column with name 'a'. + * df.stat.freqItems(Seq("a")) + * }}} + * + * @group dfops + */ + def stat: DataFrameStatFunctions = new DataFrameStatFunctions(this) + + /** * Cartesian join with another [[DataFrame]]. * * Note that cartesian joins are very expensive without an extra filter that can be pushed down. diff --git a/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala new file mode 100644 index 0000000000..42e5cbc05e --- /dev/null +++ b/sql/core/src/main/scala/org/apache/spark/sql/DataFrameStatFunctions.scala @@ -0,0 +1,68 @@ +/* +* 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 + +import org.apache.spark.annotation.Experimental +import org.apache.spark.sql.execution.stat.FrequentItems + +/** + * :: Experimental :: + * Statistic functions for [[DataFrame]]s. + */ +@Experimental +final class DataFrameStatFunctions private[sql](df: DataFrame) { + + /** + * Finding frequent items for columns, possibly with false positives. Using the + * frequent element count algorithm described in + * [[http://dx.doi.org/10.1145/762471.762473, proposed by Karp, Schenker, and Papadimitriou]]. + * The `support` should be greater than 1e-4. + * + * @param cols the names of the columns to search frequent items in. + * @param support The minimum frequency for an item to be considered `frequent`. Should be greater + * than 1e-4. + * @return A Local DataFrame with the Array of frequent items for each column. + */ + def freqItems(cols: Array[String], support: Double): DataFrame = { + FrequentItems.singlePassFreqItems(df, cols, support) + } + + /** + * Runs `freqItems` with a default `support` of 1%. + * + * @param cols the names of the columns to search frequent items in. + * @return A Local DataFrame with the Array of frequent items for each column. + */ + def freqItems(cols: Array[String]): DataFrame = { + FrequentItems.singlePassFreqItems(df, cols, 0.01) + } + + /** + * Python friendly implementation for `freqItems` + */ + def freqItems(cols: List[String], support: Double): DataFrame = { + FrequentItems.singlePassFreqItems(df, cols, support) + } + + /** + * Python friendly implementation for `freqItems` with a default `support` of 1%. + */ + def freqItems(cols: List[String]): DataFrame = { + FrequentItems.singlePassFreqItems(df, cols, 0.01) + } +} diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/FrequentItems.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/FrequentItems.scala new file mode 100644 index 0000000000..5ae7e10754 --- /dev/null +++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/stat/FrequentItems.scala @@ -0,0 +1,121 @@ +/* +* 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.execution.stat + +import scala.collection.mutable.{Map => MutableMap} + +import org.apache.spark.Logging +import org.apache.spark.sql.{Column, DataFrame, Row} +import org.apache.spark.sql.catalyst.plans.logical.LocalRelation +import org.apache.spark.sql.types.{ArrayType, StructField, StructType} + +private[sql] object FrequentItems extends Logging { + + /** A helper class wrapping `MutableMap[Any, Long]` for simplicity. */ + private class FreqItemCounter(size: Int) extends Serializable { + val baseMap: MutableMap[Any, Long] = MutableMap.empty[Any, Long] + + /** + * Add a new example to the counts if it exists, otherwise deduct the count + * from existing items. + */ + def add(key: Any, count: Long): this.type = { + if (baseMap.contains(key)) { + baseMap(key) += count + } else { + if (baseMap.size < size) { + baseMap += key -> count + } else { + // TODO: Make this more efficient... A flatMap? + baseMap.retain((k, v) => v > count) + baseMap.transform((k, v) => v - count) + } + } + this + } + + /** + * Merge two maps of counts. + * @param other The map containing the counts for that partition + */ + def merge(other: FreqItemCounter): this.type = { + other.baseMap.foreach { case (k, v) => + add(k, v) + } + this + } + } + + /** + * Finding frequent items for columns, possibly with false positives. Using the + * frequent element count algorithm described in + * [[http://dx.doi.org/10.1145/762471.762473, proposed by Karp, Schenker, and Papadimitriou]]. + * The `support` should be greater than 1e-4. + * For Internal use only. + * + * @param df The input DataFrame + * @param cols the names of the columns to search frequent items in + * @param support The minimum frequency for an item to be considered `frequent`. Should be greater + * than 1e-4. + * @return A Local DataFrame with the Array of frequent items for each column. + */ + private[sql] def singlePassFreqItems( + df: DataFrame, + cols: Seq[String], + support: Double): DataFrame = { + require(support >= 1e-4, s"support ($support) must be greater than 1e-4.") + val numCols = cols.length + // number of max items to keep counts for + val sizeOfMap = (1 / support).toInt + val countMaps = Seq.tabulate(numCols)(i => new FreqItemCounter(sizeOfMap)) + val originalSchema = df.schema + val colInfo = cols.map { name => + val index = originalSchema.fieldIndex(name) + (name, originalSchema.fields(index).dataType) + } + + val freqItems = df.select(cols.map(Column(_)):_*).rdd.aggregate(countMaps)( + seqOp = (counts, row) => { + var i = 0 + while (i < numCols) { + val thisMap = counts(i) + val key = row.get(i) + thisMap.add(key, 1L) + i += 1 + } + counts + }, + combOp = (baseCounts, counts) => { + var i = 0 + while (i < numCols) { + baseCounts(i).merge(counts(i)) + i += 1 + } + baseCounts + } + ) + val justItems = freqItems.map(m => m.baseMap.keys.toSeq) + val resultRow = Row(justItems:_*) + // append frequent Items to the column name for easy debugging + val outputCols = colInfo.map { v => + StructField(v._1 + "_freqItems", ArrayType(v._2, false)) + } + val schema = StructType(outputCols).toAttributes + new DataFrame(df.sqlContext, LocalRelation(schema, Seq(resultRow))) + } +} diff --git a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java index e5c9504d21..966d879e1f 100644 --- a/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java +++ b/sql/core/src/test/java/test/org/apache/spark/sql/JavaDataFrameSuite.java @@ -22,10 +22,7 @@ import com.google.common.primitives.Ints; import org.apache.spark.api.java.JavaRDD; import org.apache.spark.api.java.JavaSparkContext; -import org.apache.spark.sql.DataFrame; -import org.apache.spark.sql.Row; -import org.apache.spark.sql.SQLContext; -import org.apache.spark.sql.TestData$; +import org.apache.spark.sql.*; import org.apache.spark.sql.test.TestSQLContext; import org.apache.spark.sql.test.TestSQLContext$; import org.apache.spark.sql.types.*; @@ -178,5 +175,12 @@ public class JavaDataFrameSuite { Assert.assertEquals(bean.getD().get(i), d.apply(i)); } } - + + @Test + public void testFrequentItems() { + DataFrame df = context.table("testData2"); + String[] cols = new String[]{"a"}; + DataFrame results = df.stat().freqItems(cols, 0.2); + Assert.assertTrue(results.collect()[0].getSeq(0).contains(1)); + } } diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameStatSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameStatSuite.scala new file mode 100644 index 0000000000..bb1d29c71d --- /dev/null +++ b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameStatSuite.scala @@ -0,0 +1,47 @@ +/* + * 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 + +import org.scalatest.FunSuite +import org.scalatest.Matchers._ + +import org.apache.spark.sql.test.TestSQLContext +import org.apache.spark.sql.test.TestSQLContext.implicits._ + +class DataFrameStatSuite extends FunSuite { + + val sqlCtx = TestSQLContext + + test("Frequent Items") { + def toLetter(i: Int): String = (i + 96).toChar.toString + val rows = Array.tabulate(1000) { i => + if (i % 3 == 0) (1, toLetter(1), -1.0) else (i, toLetter(i), i * -1.0) + } + val df = sqlCtx.sparkContext.parallelize(rows).toDF("numbers", "letters", "negDoubles") + + val results = df.stat.freqItems(Array("numbers", "letters"), 0.1) + val items = results.collect().head + items.getSeq[Int](0) should contain (1) + items.getSeq[String](1) should contain (toLetter(1)) + + val singleColResults = df.stat.freqItems(Array("negDoubles"), 0.1) + val items2 = singleColResults.collect().head + items2.getSeq[Double](0) should contain (-1.0) + + } +} |