Github user rxin commented on a diff in the pull request: https://github.com/apache/spark/pull/6104#discussion_r30825593 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/Window.scala --- @@ -0,0 +1,222 @@ +/* + * 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 scala.language.implicitConversions + +import org.apache.spark.annotation.Experimental +import org.apache.spark.sql.catalyst.expressions._ + + +sealed private[sql] class Frame(private[sql] var boundary: FrameBoundary = null) + +/** + * :: Experimental :: + * An utility to specify the Window Frame Range. + */ +object Frame { + val currentRow: Frame = new Frame(CurrentRow) + val unbounded: Frame = new Frame() + def preceding(n: Int): Frame = if (n == 0) { + new Frame(CurrentRow) + } else { + new Frame(ValuePreceding(n)) + } + + def following(n: Int): Frame = if (n == 0) { + new Frame(CurrentRow) + } else { + new Frame(ValueFollowing(n)) + } +} + +/** + * :: Experimental :: + * A Window object with everything unset. But can build new Window object + * based on it. + */ +@Experimental +object Window extends Window() + +/** + * :: Experimental :: + * A set of methods for window function definition for aggregate expressions. + * For example: + * {{{ + * // predefine a window + * val w = Window.partitionBy("name").orderBy("id") + * .rowsBetween(Frame.unbounded, Frame.currentRow) + * df.select( + * avg("age").over(Window.partitionBy("..", "..").orderBy("..", "..") + * .rowsBetween(Frame.unbounded, Frame.currentRow)) + * ) + * + * df.select( + * avg("age").over(Window.partitionBy("..", "..").orderBy("..", "..") + * .rowsBetween(Frame.preceding(50), Frame.following(10))) + * ) + * + * }}} + * + */ +@Experimental +class Window { + private var column: Column = _ + private var partitionSpec: Seq[Expression] = Nil + private var orderSpec: Seq[SortOrder] = Nil + private var frame: WindowFrame = UnspecifiedFrame + + private def this( --- End diff -- this ctor is not necessary
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