[SPARK-7965] [SPARK-7972] [SQL] Handle expressions containing multiple window expressions and make parser match window frames in case insensitive way

JIRAs:
https://issues.apache.org/jira/browse/SPARK-7965
https://issues.apache.org/jira/browse/SPARK-7972

Author: Yin Huai <yhuai@databricks.com>

Closes #6524 from yhuai/7965-7972 and squashes the following commits:

c12c79c [Yin Huai] Add doc for returned value.
de64328 [Yin Huai] Address rxin's comments.
fc9b1ad [Yin Huai] wip
2996da4 [Yin Huai] scala style
20b65b7 [Yin Huai] Handle expressions containing multiple window expressions.
9568b21 [Yin Huai] case insensitive matches
41f633d [Yin Huai] Failed test case.

3 files changed, 134 insertions, 32 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
index df37889eed..8e9fec7070 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
@@ -633,10 +633,10 @@ class Analyzer(
    *    it into the plan tree.
    */
   object ExtractWindowExpressions extends Rule[LogicalPlan] {
-    def hasWindowFunction(projectList: Seq[NamedExpression]): Boolean =
+    private def hasWindowFunction(projectList: Seq[NamedExpression]): Boolean =
       projectList.exists(hasWindowFunction)
 
-    def hasWindowFunction(expr: NamedExpression): Boolean = {
+    private def hasWindowFunction(expr: NamedExpression): Boolean = {
       expr.find {
         case window: WindowExpression => true
         case _ => false
@@ -644,14 +644,24 @@ class Analyzer(
     }
 
     /**
-     * From a Seq of [[NamedExpression]]s, extract window expressions and
-     * other regular expressions.
+     * From a Seq of [[NamedExpression]]s, extract expressions containing window expressions and
+     * other regular expressions that do not contain any window expression. For example, for
+     * `col1, Sum(col2 + col3) OVER (PARTITION BY col4 ORDER BY col5)`, we will extract
+     * `col1`, `col2 + col3`, `col4`, and `col5` out and replace them appearances in
+     * the window expression as attribute references. So, the first returned value will be
+     * `[Sum(_w0) OVER (PARTITION BY _w1 ORDER BY _w2)]` and the second returned value will be
+     * [col1, col2 + col3 as _w0, col4 as _w1, col5 as _w2].
+     *
+     * @return (seq of expressions containing at lease one window expressions,
+     *          seq of non-window expressions)
      */
-    def extract(
+    private def extract(
         expressions: Seq[NamedExpression]): (Seq[NamedExpression], Seq[NamedExpression]) = {
-      // First, we simple partition the input expressions to two part, one having
-      // WindowExpressions and another one without WindowExpressions.
-      val (windowExpressions, regularExpressions) = expressions.partition(hasWindowFunction)
+      // First, we partition the input expressions to two part. For the first part,
+      // every expression in it contain at least one WindowExpression.
+      // Expressions in the second part do not have any WindowExpression.
+      val (expressionsWithWindowFunctions, regularExpressions) =
+        expressions.partition(hasWindowFunction)
 
       // Then, we need to extract those regular expressions used in the WindowExpression.
       // For example, when we have col1 - Sum(col2 + col3) OVER (PARTITION BY col4 ORDER BY col5),
@@ -660,8 +670,8 @@ class Analyzer(
       val extractedExprBuffer = new ArrayBuffer[NamedExpression]()
       def extractExpr(expr: Expression): Expression = expr match {
         case ne: NamedExpression =>
-          // If a named expression is not in regularExpressions, add extract it and replace it
-          // with an AttributeReference.
+          // If a named expression is not in regularExpressions, add it to
+          // extractedExprBuffer and replace it with an AttributeReference.
           val missingExpr =
             AttributeSet(Seq(expr)) -- (regularExpressions ++ extractedExprBuffer)
           if (missingExpr.nonEmpty) {
@@ -678,8 +688,9 @@ class Analyzer(
           withName.toAttribute
       }
 
-      // Now, we extract expressions from windowExpressions by using extractExpr.
-      val newWindowExpressions = windowExpressions.map {
+      // Now, we extract regular expressions from expressionsWithWindowFunctions
+      // by using extractExpr.
+      val newExpressionsWithWindowFunctions = expressionsWithWindowFunctions.map {
         _.transform {
           // Extracts children expressions of a WindowFunction (input parameters of
           // a WindowFunction).
@@ -705,37 +716,80 @@ class Analyzer(
         }.asInstanceOf[NamedExpression]
       }
 
-      (newWindowExpressions, regularExpressions ++ extractedExprBuffer)
-    }
+      (newExpressionsWithWindowFunctions, regularExpressions ++ extractedExprBuffer)
+    } // end of extract
 
     /**
      * Adds operators for Window Expressions. Every Window operator handles a single Window Spec.
      */
-    def addWindow(windowExpressions: Seq[NamedExpression], child: LogicalPlan): LogicalPlan = {
-      // First, we group window expressions based on their Window Spec.
-      val groupedWindowExpression = windowExpressions.groupBy { expr =>
-        val windowSpec = expr.collectFirst {
+    private def addWindow(
+        expressionsWithWindowFunctions: Seq[NamedExpression],
+        child: LogicalPlan): LogicalPlan = {
+      // First, we need to extract all WindowExpressions from expressionsWithWindowFunctions
+      // and put those extracted WindowExpressions to extractedWindowExprBuffer.
+      // This step is needed because it is possible that an expression contains multiple
+      // WindowExpressions with different Window Specs.
+      // After extracting WindowExpressions, we need to construct a project list to generate
+      // expressionsWithWindowFunctions based on extractedWindowExprBuffer.
+      // For example, for "sum(a) over (...) / sum(b) over (...)", we will first extract
+      // "sum(a) over (...)" and "sum(b) over (...)" out, and assign "_we0" as the alias to
+      // "sum(a) over (...)" and "_we1" as the alias to "sum(b) over (...)".
+      // Then, the projectList will be [_we0/_we1].
+      val extractedWindowExprBuffer = new ArrayBuffer[NamedExpression]()
+      val newExpressionsWithWindowFunctions = expressionsWithWindowFunctions.map {
+        // We need to use transformDown because we want to trigger
+        // "case alias @ Alias(window: WindowExpression, _)" first.
+        _.transformDown {
+          case alias @ Alias(window: WindowExpression, _) =>
+            // If a WindowExpression has an assigned alias, just use it.
+            extractedWindowExprBuffer += alias
+            alias.toAttribute
+          case window: WindowExpression =>
+            // If there is no alias assigned to the WindowExpressions. We create an
+            // internal column.
+            val withName = Alias(window, s"_we${extractedWindowExprBuffer.length}")()
+            extractedWindowExprBuffer += withName
+            withName.toAttribute
+        }.asInstanceOf[NamedExpression]
+      }
+
+      // Second, we group extractedWindowExprBuffer based on their Window Spec.
+      val groupedWindowExpressions = extractedWindowExprBuffer.groupBy { expr =>
+        val distinctWindowSpec = expr.collect {
           case window: WindowExpression => window.windowSpec
+        }.distinct
+
+        // We do a final check and see if we only have a single Window Spec defined in an
+        // expressions.
+        if (distinctWindowSpec.length == 0 ) {
+          failAnalysis(s"$expr does not have any WindowExpression.")
+        } else if (distinctWindowSpec.length > 1) {
+          // newExpressionsWithWindowFunctions only have expressions with a single
+          // WindowExpression. If we reach here, we have a bug.
+          failAnalysis(s"$expr has multiple Window Specifications ($distinctWindowSpec)." +
+            s"Please file a bug report with this error message, stack trace, and the query.")
+        } else {
+          distinctWindowSpec.head
         }
-        windowSpec.getOrElse(
-          failAnalysis(s"$windowExpressions does not have any WindowExpression."))
       }.toSeq
 
-      // For every Window Spec, we add a Window operator and set currentChild as the child of it.
+      // Third, for every Window Spec, we add a Window operator and set currentChild as the
+      // child of it.
       var currentChild = child
       var i = 0
-      while (i < groupedWindowExpression.size) {
-        val (windowSpec, windowExpressions) = groupedWindowExpression(i)
+      while (i < groupedWindowExpressions.size) {
+        val (windowSpec, windowExpressions) = groupedWindowExpressions(i)
         // Set currentChild to the newly created Window operator.
         currentChild = Window(currentChild.output, windowExpressions, windowSpec, currentChild)
 
-        // Move to next WindowExpression.
+        // Move to next Window Spec.
         i += 1
       }
 
-      // We return the top operator.
-      currentChild
-    }
+      // Finally, we create a Project to output currentChild's output
+      // newExpressionsWithWindowFunctions.
+      Project(currentChild.output ++ newExpressionsWithWindowFunctions, currentChild)
+    } // end of addWindow
 
     // We have to use transformDown at here to make sure the rule of
     // "Aggregate with Having clause" will be triggered.
diff --git a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
index 253bf11252..a5ca3613c5 100644
--- a/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
+++ b/sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala
@@ -1561,6 +1561,10 @@ https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation%2C+Cube%2C
          """.stripMargin)
   }
 
+  /* Case insensitive matches for Window Specification */
+  val PRECEDING = "(?i)preceding".r
+  val FOLLOWING = "(?i)following".r
+  val CURRENT = "(?i)current".r
   def nodesToWindowSpecification(nodes: Seq[ASTNode]): WindowSpec = nodes match {
     case Token(windowName, Nil) :: Nil =>
       // Refer to a window spec defined in the window clause.
@@ -1614,11 +1618,19 @@ https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation%2C+Cube%2C
         } else {
           val frameType = rowFrame.map(_ => RowFrame).getOrElse(RangeFrame)
           def nodeToBoundary(node: Node): FrameBoundary = node match {
-            case Token("preceding", Token(count, Nil) :: Nil) =>
-              if (count == "unbounded") UnboundedPreceding else ValuePreceding(count.toInt)
-            case Token("following", Token(count, Nil) :: Nil) =>
-              if (count == "unbounded") UnboundedFollowing else ValueFollowing(count.toInt)
-            case Token("current", Nil) => CurrentRow
+            case Token(PRECEDING(), Token(count, Nil) :: Nil) =>
+              if (count.toLowerCase() == "unbounded") {
+                UnboundedPreceding
+              } else {
+                ValuePreceding(count.toInt)
+              }
+            case Token(FOLLOWING(), Token(count, Nil) :: Nil) =>
+              if (count.toLowerCase() == "unbounded") {
+                UnboundedFollowing
+              } else {
+                ValueFollowing(count.toInt)
+              }
+            case Token(CURRENT(), Nil) => CurrentRow
             case _ =>
               throw new NotImplementedError(
                 s"""No parse rules for the Window Frame Boundary based on Node ${node.getName}
diff --git a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/SQLQuerySuite.scala b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/SQLQuerySuite.scala
index 27863a6014..aba3becb1b 100644
--- a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/SQLQuerySuite.scala
+++ b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/SQLQuerySuite.scala
@@ -780,6 +780,42 @@ class SQLQuerySuite extends QueryTest {
       ).map(i => Row(i._1, i._2, i._3, i._4)))
   }
 
+  test("window function: multiple window expressions in a single expression") {
+    val nums = sparkContext.parallelize(1 to 10).map(x => (x, x % 2)).toDF("x", "y")
+    nums.registerTempTable("nums")
+
+    val expected =
+      Row(1, 1, 1, 55, 1, 57) ::
+      Row(0, 2, 3, 55, 2, 60) ::
+      Row(1, 3, 6, 55, 4, 65) ::
+      Row(0, 4, 10, 55, 6, 71) ::
+      Row(1, 5, 15, 55, 9, 79) ::
+      Row(0, 6, 21, 55, 12, 88) ::
+      Row(1, 7, 28, 55, 16, 99) ::
+      Row(0, 8, 36, 55, 20, 111) ::
+      Row(1, 9, 45, 55, 25, 125) ::
+      Row(0, 10, 55, 55, 30, 140) :: Nil
+
+    val actual = sql(
+      """
+        |SELECT
+        |  y,
+        |  x,
+        |  sum(x) OVER w1 AS running_sum,
+        |  sum(x) OVER w2 AS total_sum,
+        |  sum(x) OVER w3 AS running_sum_per_y,
+        |  ((sum(x) OVER w1) + (sum(x) OVER w2) + (sum(x) OVER w3)) as combined2
+        |FROM nums
+        |WINDOW w1 AS (ORDER BY x ROWS BETWEEN UnBOUNDED PRECEDiNG AND CuRRENT RoW),
+        |       w2 AS (ORDER BY x ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOuNDED FoLLOWING),
+        |       w3 AS (PARTITION BY y ORDER BY x ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
+      """.stripMargin)
+
+    checkAnswer(actual, expected)
+
+    dropTempTable("nums")
+  }
+
   test("test case key when") {
     (1 to 5).map(i => (i, i.toString)).toDF("k", "v").registerTempTable("t")
     checkAnswer(