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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