[SPARK-8279][SQL]Add math function round

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala

@@ -116,6 +116,7 @@ object FunctionRegistry {
     expression[Pow]("power"),
     expression[UnaryPositive]("positive"),
     expression[Rint]("rint"),
+    expression[Round]("round"),
     expression[ShiftLeft]("shiftleft"),
     expression[ShiftRight]("shiftright"),
     expression[ShiftRightUnsigned]("shiftrightunsigned"),

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala

@@ -19,8 +19,10 @@ package org.apache.spark.sql.catalyst.expressions
 
 import java.{lang => jl}
 
-import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.analysis.TypeCheckResult
+import org.apache.spark.sql.catalyst.analysis.TypeCheckResult.{TypeCheckSuccess, TypeCheckFailure}
 import org.apache.spark.sql.catalyst.expressions.codegen._
+import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.types._
 import org.apache.spark.unsafe.types.UTF8String
 
@@ -520,3 +522,202 @@ case class Logarithm(left: Expression, right: Expression)
     """
   }
 }
+
+/**
+ * Round the `child`'s result to `scale` decimal place when `scale` >= 0
+ * or round at integral part when `scale` < 0.
+ * For example, round(31.415, 2) would eval to 31.42 and round(31.415, -1) would eval to 30.
+ *
+ * Child of IntegralType would eval to itself when `scale` >= 0.
+ * Child of FractionalType whose value is NaN or Infinite would always eval to itself.
+ *
+ * Round's dataType would always equal to `child`'s dataType except for [[DecimalType.Fixed]],
+ * which leads to scale update in DecimalType's [[PrecisionInfo]]
+ *
+ * @param child expr to be round, all [[NumericType]] is allowed as Input
+ * @param scale new scale to be round to, this should be a constant int at runtime
+ */
+case class Round(child: Expression, scale: Expression)
+  extends BinaryExpression with ExpectsInputTypes {
+
+  import BigDecimal.RoundingMode.HALF_UP
+
+  def this(child: Expression) = this(child, Literal(0))
+
+  override def left: Expression = child
+  override def right: Expression = scale
+
+  // round of Decimal would eval to null if it fails to `changePrecision`
+  override def nullable: Boolean = true
+
+  override def foldable: Boolean = child.foldable
+
+  override lazy val dataType: DataType = child.dataType match {
+    // if the new scale is bigger which means we are scaling up,
+    // keep the original scale as `Decimal` does
+    case DecimalType.Fixed(p, s) => DecimalType(p, if (_scale > s) s else _scale)
+    case t => t
+  }
+
+  override def inputTypes: Seq[AbstractDataType] = Seq(NumericType, IntegerType)
+
+  override def checkInputDataTypes(): TypeCheckResult = {
+    super.checkInputDataTypes() match {
+      case TypeCheckSuccess =>
+        if (scale.foldable) {
+          TypeCheckSuccess
+        } else {
+          TypeCheckFailure("Only foldable Expression is allowed for scale arguments")
+        }
+      case f => f
+    }
+  }
+
+  // Avoid repeated evaluation since `scale` is a constant int,
+  // avoid unnecessary `child` evaluation in both codegen and non-codegen eval
+  // by checking if scaleV == null as well.
+  private lazy val scaleV: Any = scale.eval(EmptyRow)
+  private lazy val _scale: Int = scaleV.asInstanceOf[Int]
+
+  override def eval(input: InternalRow): Any = {
+    if (scaleV == null) { // if scale is null, no need to eval its child at all
+      null
+    } else {
+      val evalE = child.eval(input)
+      if (evalE == null) {
+        null
+      } else {
+        nullSafeEval(evalE)
+      }
+    }
+  }
+
+  // not overriding since _scale is a constant int at runtime
+  def nullSafeEval(input1: Any): Any = {
+    child.dataType match {
+      case _: DecimalType =>
+        val decimal = input1.asInstanceOf[Decimal]
+        if (decimal.changePrecision(decimal.precision, _scale)) decimal else null
+      case ByteType =>
+        BigDecimal(input1.asInstanceOf[Byte]).setScale(_scale, HALF_UP).toByte
+      case ShortType =>
+        BigDecimal(input1.asInstanceOf[Short]).setScale(_scale, HALF_UP).toShort
+      case IntegerType =>
+        BigDecimal(input1.asInstanceOf[Int]).setScale(_scale, HALF_UP).toInt
+      case LongType =>
+        BigDecimal(input1.asInstanceOf[Long]).setScale(_scale, HALF_UP).toLong
+      case FloatType =>
+        val f = input1.asInstanceOf[Float]
+        if (f.isNaN || f.isInfinite) {
+          f
+        } else {
+          BigDecimal(f).setScale(_scale, HALF_UP).toFloat
+        }
+      case DoubleType =>
+        val d = input1.asInstanceOf[Double]
+        if (d.isNaN || d.isInfinite) {
+          d
+        } else {
+          BigDecimal(d).setScale(_scale, HALF_UP).toDouble
+        }
+    }
+  }
+
+  override def genCode(ctx: CodeGenContext, ev: GeneratedExpressionCode): String = {
+    val ce = child.gen(ctx)
+
+    val evaluationCode = child.dataType match {
+      case _: DecimalType =>
+        s"""
+        if (${ce.primitive}.changePrecision(${ce.primitive}.precision(), ${_scale})) {
+          ${ev.primitive} = ${ce.primitive};
+        } else {
+          ${ev.isNull} = true;
+        }"""
+      case ByteType =>
+        if (_scale < 0) {
+          s"""
+          ${ev.primitive} = new java.math.BigDecimal(${ce.primitive}).
+            setScale(${_scale}, java.math.BigDecimal.ROUND_HALF_UP).byteValue();"""
+        } else {
+          s"${ev.primitive} = ${ce.primitive};"
+        }
+      case ShortType =>
+        if (_scale < 0) {
+          s"""
+          ${ev.primitive} = new java.math.BigDecimal(${ce.primitive}).
+            setScale(${_scale}, java.math.BigDecimal.ROUND_HALF_UP).shortValue();"""
+        } else {
+          s"${ev.primitive} = ${ce.primitive};"
+        }
+      case IntegerType =>
+        if (_scale < 0) {
+          s"""
+          ${ev.primitive} = new java.math.BigDecimal(${ce.primitive}).
+            setScale(${_scale}, java.math.BigDecimal.ROUND_HALF_UP).intValue();"""
+        } else {
+          s"${ev.primitive} = ${ce.primitive};"
+        }
+      case LongType =>
+        if (_scale < 0) {
+          s"""
+          ${ev.primitive} = new java.math.BigDecimal(${ce.primitive}).
+            setScale(${_scale}, java.math.BigDecimal.ROUND_HALF_UP).longValue();"""
+        } else {
+          s"${ev.primitive} = ${ce.primitive};"
+        }
+      case FloatType => // if child eval to NaN or Infinity, just return it.
+        if (_scale == 0) {
+          s"""
+            if (Float.isNaN(${ce.primitive}) || Float.isInfinite(${ce.primitive})){
+              ${ev.primitive} = ${ce.primitive};
+            } else {
+              ${ev.primitive} = Math.round(${ce.primitive});
+            }"""
+        } else {
+          s"""
+            if (Float.isNaN(${ce.primitive}) || Float.isInfinite(${ce.primitive})){
+              ${ev.primitive} = ${ce.primitive};
+            } else {
+              ${ev.primitive} = java.math.BigDecimal.valueOf(${ce.primitive}).
+                setScale(${_scale}, java.math.BigDecimal.ROUND_HALF_UP).floatValue();
+            }"""
+        }
+      case DoubleType => // if child eval to NaN or Infinity, just return it.
+        if (_scale == 0) {
+          s"""
+            if (Double.isNaN(${ce.primitive}) || Double.isInfinite(${ce.primitive})){
+              ${ev.primitive} = ${ce.primitive};
+            } else {
+              ${ev.primitive} = Math.round(${ce.primitive});
+            }"""
+        } else {
+          s"""
+            if (Double.isNaN(${ce.primitive}) || Double.isInfinite(${ce.primitive})){
+              ${ev.primitive} = ${ce.primitive};
+            } else {
+              ${ev.primitive} = java.math.BigDecimal.valueOf(${ce.primitive}).
+                setScale(${_scale}, java.math.BigDecimal.ROUND_HALF_UP).doubleValue();
+            }"""
+        }
+    }
+
+    if (scaleV == null) { // if scale is null, no need to eval its child at all
+      s"""
+        boolean ${ev.isNull} = true;
+        ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+      """
+    } else {
+      s"""
+        ${ce.code}
+        boolean ${ev.isNull} = ${ce.isNull};
+        ${ctx.javaType(dataType)} ${ev.primitive} = ${ctx.defaultValue(dataType)};
+        if (!${ev.isNull}) {
+          $evaluationCode
+        }
+      """
+    }
+  }
+
+  override def prettyName: String = "round"
+}

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/ExpressionTypeCheckingSuite.scala

@@ -52,6 +52,13 @@ class ExpressionTypeCheckingSuite extends SparkFunSuite {
       s"differing types in ${expr.getClass.getSimpleName} (IntegerType and BooleanType).")
   }
 
+  def assertErrorWithImplicitCast(expr: Expression, errorMessage: String): Unit = {
+    val e = intercept[AnalysisException] {
+      assertSuccess(expr)
+    }
+    assert(e.getMessage.contains(errorMessage))
+  }
+
   test("check types for unary arithmetic") {
     assertError(UnaryMinus('stringField), "operator - accepts numeric type")
     assertError(Abs('stringField), "function abs accepts numeric type")
@@ -171,4 +178,14 @@ class ExpressionTypeCheckingSuite extends SparkFunSuite {
       CreateNamedStruct(Seq('a.string.at(0), "a", "b", 2.0)),
         "Odd position only allow foldable and not-null StringType expressions")
   }
+
+  test("check types for ROUND") {
+    assertErrorWithImplicitCast(Round(Literal(null), 'booleanField),
+      "data type mismatch: argument 2 is expected to be of type int")
+    assertErrorWithImplicitCast(Round(Literal(null), 'complexField),
+      "data type mismatch: argument 2 is expected to be of type int")
+    assertSuccess(Round(Literal(null), Literal(null)))
+    assertError(Round('booleanField, 'intField),
+      "data type mismatch: argument 1 is expected to be of type numeric")
+  }
 }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/MathFunctionsSuite.scala

@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.catalyst.expressions
 
+import scala.math.BigDecimal.RoundingMode
+
 import com.google.common.math.LongMath
 
 import org.apache.spark.SparkFunSuite
@@ -336,4 +338,46 @@ class MathFunctionsSuite extends SparkFunSuite with ExpressionEvalHelper {
       null,
       create_row(null))
   }
+
+  test("round") {
+    val domain = -6 to 6
+    val doublePi: Double = math.Pi
+    val shortPi: Short = 31415
+    val intPi: Int = 314159265
+    val longPi: Long = 31415926535897932L
+    val bdPi: BigDecimal = BigDecimal(31415927L, 7)
+
+    val doubleResults: Seq[Double] = Seq(0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 3.0, 3.1, 3.14, 3.142,
+      3.1416, 3.14159, 3.141593)
+
+    val shortResults: Seq[Short] = Seq[Short](0, 0, 30000, 31000, 31400, 31420) ++
+      Seq.fill[Short](7)(31415)
+
+    val intResults: Seq[Int] = Seq(314000000, 314200000, 314160000, 314159000, 314159300,
+      314159270) ++ Seq.fill(7)(314159265)
+
+    val longResults: Seq[Long] = Seq(31415926536000000L, 31415926535900000L,
+      31415926535900000L, 31415926535898000L, 31415926535897900L, 31415926535897930L) ++
+      Seq.fill(7)(31415926535897932L)
+
+    val bdResults: Seq[BigDecimal] = Seq(BigDecimal(3.0), BigDecimal(3.1), BigDecimal(3.14),
+      BigDecimal(3.142), BigDecimal(3.1416), BigDecimal(3.14159),
+      BigDecimal(3.141593), BigDecimal(3.1415927))
+
+    domain.zipWithIndex.foreach { case (scale, i) =>
+      checkEvaluation(Round(doublePi, scale), doubleResults(i), EmptyRow)
+      checkEvaluation(Round(shortPi, scale), shortResults(i), EmptyRow)
+      checkEvaluation(Round(intPi, scale), intResults(i), EmptyRow)
+      checkEvaluation(Round(longPi, scale), longResults(i), EmptyRow)
+    }
+
+    // round_scale > current_scale would result in precision increase
+    // and not allowed by o.a.s.s.types.Decimal.changePrecision, therefore null
+    (0 to 7).foreach { i =>
+      checkEvaluation(Round(bdPi, i), bdResults(i), EmptyRow)
+    }
+    (8 to 10).foreach { scale =>
+      checkEvaluation(Round(bdPi, scale), null, EmptyRow)
+    }
+  }
 }

sql/catalyst/src/test/scala/org/apache/spark/sql/types/decimal/DecimalSuite.scala

@@ -24,14 +24,14 @@ import org.scalatest.PrivateMethodTester
 import scala.language.postfixOps
 
 class DecimalSuite extends SparkFunSuite with PrivateMethodTester {
-  test("creating decimals") {
-    /** Check that a Decimal has the given string representation, precision and scale */
-    def checkDecimal(d: Decimal, string: String, precision: Int, scale: Int): Unit = {
-      assert(d.toString === string)
-      assert(d.precision === precision)
-      assert(d.scale === scale)
-    }
+  /** Check that a Decimal has the given string representation, precision and scale */
+  private def checkDecimal(d: Decimal, string: String, precision: Int, scale: Int): Unit = {
+    assert(d.toString === string)
+    assert(d.precision === precision)
+    assert(d.scale === scale)
+  }
 
+  test("creating decimals") {
     checkDecimal(new Decimal(), "0", 1, 0)
     checkDecimal(Decimal(BigDecimal("10.030")), "10.030", 5, 3)
     checkDecimal(Decimal(BigDecimal("10.030"), 4, 1), "10.0", 4, 1)
@@ -53,6 +53,15 @@ class DecimalSuite extends SparkFunSuite with PrivateMethodTester {
     intercept[IllegalArgumentException](Decimal(1e17.toLong, 17, 0))
   }
 
+  test("creating decimals with negative scale") {
+    checkDecimal(Decimal(BigDecimal("98765"), 5, -3), "9.9E+4", 5, -3)
+    checkDecimal(Decimal(BigDecimal("314.159"), 6, -2), "3E+2", 6, -2)
+    checkDecimal(Decimal(BigDecimal(1.579e12), 4, -9), "1.579E+12", 4, -9)
+    checkDecimal(Decimal(BigDecimal(1.579e12), 4, -10), "1.58E+12", 4, -10)
+    checkDecimal(Decimal(103050709L, 9, -10), "1.03050709E+18", 9, -10)
+    checkDecimal(Decimal(1e8.toLong, 10, -10), "1.00000000E+18", 10, -10)
+  }
+
   test("double and long values") {
     /** Check that a Decimal converts to the given double and long values */
     def checkValues(d: Decimal, doubleValue: Double, longValue: Long): Unit = {

sql/core/src/main/scala/org/apache/spark/sql/functions.scala

@@ -1385,6 +1385,38 @@ object functions {
    */
   def rint(columnName: String): Column = rint(Column(columnName))
 
+  /**
+   * Returns the value of the column `e` rounded to 0 decimal places.
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def round(e: Column): Column = round(e.expr, 0)
+
+  /**
+   * Returns the value of the given column rounded to 0 decimal places.
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def round(columnName: String): Column = round(Column(columnName), 0)
+
+  /**
+   * Returns the value of `e` rounded to `scale` decimal places.
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def round(e: Column, scale: Int): Column = Round(e.expr, Literal(scale))
+
+  /**
+   * Returns the value of the given column rounded to `scale` decimal places.
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def round(columnName: String, scale: Int): Column = round(Column(columnName), scale)
+
   /**
    * Shift the the given value numBits left. If the given value is a long value, this function
    * will return a long value else it will return an integer value.