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From: cloud-fan <git@git.apache.org>
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Subject: [GitHub] spark pull request #18540: [SPARK-19451][SQL] rangeBetween method should acc...
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Message-Id: <20170713071102.97C74E109B@git1-us-west.apache.org>
Date: Thu, 13 Jul 2017 07:11:02 +0000 (UTC)
archived-at: Thu, 13 Jul 2017 07:11:05 -0000

Github user cloud-fan commented on a diff in the pull request:

    https://github.com/apache/spark/pull/18540#discussion_r127142649
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala ---
    @@ -106,173 +105,164 @@ case class WindowSpecReference(name: String) extends WindowSpec
     /**
      * The trait used to represent the type of a Window Frame.
      */
    -sealed trait FrameType
    +sealed trait FrameType {
    +  def inputType: AbstractDataType
    +  def sql: String
    +}
     
     /**
    - * RowFrame treats rows in a partition individually. When a [[ValuePreceding]]
    - * or a [[ValueFollowing]] is used as its [[FrameBoundary]], the value is considered
    - * as a physical offset.
    + * RowFrame treats rows in a partition individually. Values used in a row frame are considered
    + * to be physical offsets.
      * For example, `ROW BETWEEN 1 PRECEDING AND 1 FOLLOWING` represents a 3-row frame,
      * from the row that precedes the current row to the row that follows the current row.
      */
    -case object RowFrame extends FrameType
    +case object RowFrame extends FrameType {
    +  override def inputType: AbstractDataType = IntegerType
    +  override def sql: String = "ROWS"
    +}
     
     /**
    - * RangeFrame treats rows in a partition as groups of peers.
    - * All rows having the same `ORDER BY` ordering are considered as peers.
    - * When a [[ValuePreceding]] or a [[ValueFollowing]] is used as its [[FrameBoundary]],
    - * the value is considered as a logical offset.
    + * RangeFrame treats rows in a partition as groups of peers. All rows having the same `ORDER BY`
    + * ordering are considered as peers. Values used in a range frame are considered to be logical
    + * offsets.
      * For example, assuming the value of the current row's `ORDER BY` expression `expr` is `v`,
      * `RANGE BETWEEN 1 PRECEDING AND 1 FOLLOWING` represents a frame containing rows whose values
      * `expr` are in the range of [v-1, v+1].
      *
      * If `ORDER BY` clause is not defined, all rows in the partition are considered as peers
      * of the current row.
      */
    -case object RangeFrame extends FrameType
    +case object RangeFrame extends FrameType {
    +  override def inputType: AbstractDataType = TypeCollection.NumericAndInterval
    +  override def sql: String = "RANGE"
    +}
     
     /**
    - * The trait used to represent the type of a Window Frame Boundary.
    + * The trait used to represent special boundaries used in a window frame.
      */
    -sealed trait FrameBoundary {
    -  def notFollows(other: FrameBoundary): Boolean
    -}
    +sealed trait SpecialFrameBoundary
    +
    +/** UNBOUNDED boundary. */
    +case object Unbounded extends SpecialFrameBoundary
    +
    +/** CURRENT ROW boundary. */
    +case object CurrentRow extends SpecialFrameBoundary
     
     /**
    - * Extractor for making working with frame boundaries easier.
    + * Represents a window frame.
      */
    -object FrameBoundary {
    -  def apply(boundary: FrameBoundary): Option[Int] = unapply(boundary)
    -  def unapply(boundary: FrameBoundary): Option[Int] = boundary match {
    -    case CurrentRow => Some(0)
    -    case ValuePreceding(offset) => Some(-offset)
    -    case ValueFollowing(offset) => Some(offset)
    -    case _ => None
    -  }
    +sealed trait WindowFrame extends Expression with Unevaluable {
    +  override lazy val children: Seq[Expression] = Nil
    +  override def dataType: DataType = throw new UnsupportedOperationException("dataType")
    +  override def foldable: Boolean = false
    +  override def nullable: Boolean = false
     }
     
    -/** UNBOUNDED PRECEDING boundary. */
    -case object UnboundedPreceding extends FrameBoundary {
    -  def notFollows(other: FrameBoundary): Boolean = other match {
    -    case UnboundedPreceding => true
    -    case vp: ValuePreceding => true
    -    case CurrentRow => true
    -    case vf: ValueFollowing => true
    -    case UnboundedFollowing => true
    -  }
    +/** Used as a placeholder when a frame specification is not defined. */
    +case object UnspecifiedFrame extends WindowFrame
     
    -  override def toString: String = "UNBOUNDED PRECEDING"
    -}
    +/**
    + * A specified Window Frame. The val lower/uppper can be either a foldable [[Expression]] or a
    + * [[SpecialFrameBoundary]].
    --- End diff --
    
    can we make `SpecialFrameBoundary` an expression?


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