[SPARK-8213][SQL]Add function factorial

Author: zhichao.li <zhichao.li@intel.com>

Closes #6822 from zhichao-li/factorial and squashes the following commits:

26edf4f [zhichao.li] add factorial

2 files changed, 28 insertions, 1 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
index 4ee1fb8374..0d5d49c3dd 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/functions.scala
@@ -1023,6 +1023,22 @@ object functions {
   def expm1(columnName: String): Column = expm1(Column(columnName))
 
   /**
+   * Computes the factorial of the given value.
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def factorial(e: Column): Column = Factorial(e.expr)
+
+  /**
+   * Computes the factorial of the given column.
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def factorial(columnName: String): Column = factorial(Column(columnName))
+
+  /**
    * Computes the floor of the given value.
    *
    * @group math_funcs
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/MathExpressionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/MathExpressionsSuite.scala
index 4c5696deaf..dc8f994adb 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/MathExpressionsSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/MathExpressionsSuite.scala
@@ -20,7 +20,6 @@ package org.apache.spark.sql
 import org.apache.spark.sql.functions._
 import org.apache.spark.sql.functions.{log => logarithm}
 
-
 private object MathExpressionsTestData {
   case class DoubleData(a: java.lang.Double, b: java.lang.Double)
   case class NullDoubles(a: java.lang.Double)
@@ -183,6 +182,18 @@ class MathExpressionsSuite extends QueryTest {
     testOneToOneMathFunction(floor, math.floor)
   }
 
+  test("factorial") {
+    val df = (0 to 5).map(i => (i, i)).toDF("a", "b")
+    checkAnswer(
+      df.select(factorial('a)),
+      Seq(Row(1), Row(1), Row(2), Row(6), Row(24), Row(120))
+    )
+    checkAnswer(
+      df.selectExpr("factorial(a)"),
+      Seq(Row(1), Row(1), Row(2), Row(6), Row(24), Row(120))
+    )
+  }
+
   test("rint") {
     testOneToOneMathFunction(rint, math.rint)
   }