Github user pwendell commented on a diff in the pull request:
https://github.com/apache/spark/pull/136#discussion_r10635447
--- Diff: core/src/main/scala/org/apache/spark/rdd/SlidedRDD.scala ---
@@ -0,0 +1,102 @@
+/*
+ * 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.rdd
+
+import scala.collection.mutable
+import scala.reflect.ClassTag
+
+import org.apache.spark.{TaskContext, Partition}
+
+private[spark]
+class SlidedRDDPartition[T](val idx: Int, val prev: Partition, val tail:
Array[T])
+ extends Partition with Serializable {
+ override val index: Int = idx
+}
+
+/**
+ * Represents a RDD from grouping items of its parent RDD in fixed size
blocks by passing a sliding
+ * window over them. The ordering is first based on the partition index
and then the ordering of
+ * items within each partition. This is similar to sliding in Scala
collections, except that it
+ * becomes an empty RDD if the window size is greater than the total
number of items. It needs to
+ * trigger a Spark job if the parent RDD has more than one partitions.
+ *
+ * @param parent the parent RDD
+ * @param windowSize the window size, must be greater than 1
+ *
+ * @see [[org.apache.spark.rdd.RDD#sliding]]
+ */
+private[spark]
+class SlidedRDD[T: ClassTag](@transient val parent: RDD[T], val
windowSize: Int)
+ extends RDD[Array[T]](parent) {
+
+ require(windowSize > 1, "Window size must be greater than 1.")
--- End diff --
It would be nice to also print the provided window size. E.g. if it's
negative or something due to an overflow people might be confused to get this
error.
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