[SPARK-8207] [SQL] Add math function bin

JIRA: https://issues.apache.org/jira/browse/SPARK-8207

Author: Liang-Chi Hsieh <viirya@gmail.com>

Closes #6721 from viirya/expr_bin and squashes the following commits:

07e1c8f [Liang-Chi Hsieh] Remove AbstractUnaryMathExpression and let BIN inherit UnaryExpression.
0677f1a [Liang-Chi Hsieh] For comments.
cf62b95 [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
0cf20f2 [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
dea9c12 [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
d4f4774 [Liang-Chi Hsieh] Add @ignore_unicode_prefix.
7a0196f [Liang-Chi Hsieh] Fix python style.
ac2bacd [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
a0a2d0f [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
4cb764d [Liang-Chi Hsieh] For comments.
0f78682 [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
c0c3197 [Liang-Chi Hsieh] Add bin to FunctionRegistry.
824f761 [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into expr_bin
50e0c3b [Liang-Chi Hsieh] Add math function bin(a: long): string.

2 files changed, 28 insertions, 0 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 d8a91bead7..40ae9f5df8 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
@@ -890,6 +890,24 @@ object functions {
   def atan2(l: Double, rightName: String): Column = atan2(l, Column(rightName))
 
   /**
+   * An expression that returns the string representation of the binary value of the given long
+   * column. For example, bin("12") returns "1100".
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def bin(e: Column): Column = Bin(e.expr)
+
+  /**
+   * An expression that returns the string representation of the binary value of the given long
+   * column. For example, bin("12") returns "1100".
+   *
+   * @group math_funcs
+   * @since 1.5.0
+   */
+  def bin(columnName: String): Column = bin(Column(columnName))
+
+  /**
    * Computes the cube-root of the given value.
    *
    * @group math_funcs
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
index cfd23867a9..70819fe287 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameFunctionsSuite.scala
@@ -110,6 +110,16 @@ class DataFrameFunctionsSuite extends QueryTest {
       testData2.collect().toSeq.map(r => Row(~r.getInt(0))))
   }
 
+  test("bin") {
+    val df = Seq[(Integer, Integer)]((12, null)).toDF("a", "b")
+    checkAnswer(
+      df.select(bin("a"), bin("b")),
+      Row("1100", null))
+    checkAnswer(
+      df.selectExpr("bin(a)", "bin(b)"),
+      Row("1100", null))
+  }
+
   test("if function") {
     val df = Seq((1, 2)).toDF("a", "b")
     checkAnswer(