[SPARK-8227][SQL]Add function unhex

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

@@ -156,6 +156,7 @@ object FunctionRegistry {
  expression[Substring]("substr"),
  expression[Substring]("substring"),
  expression[Upper]("ucase"),
+ expression[UnHex]("unhex"),
  expression[Upper]("upper")
  )
 

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

@@ -354,6 +354,58 @@ case class Pow(left: Expression, right: Expression)
  }
 }
 
+/**
+ * Performs the inverse operation of HEX.
+ * Resulting characters are returned as a byte array.
+ */
+case class UnHex(child: Expression) extends UnaryExpression with Serializable {
+
+ override def dataType: DataType = BinaryType
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ if (child.dataType.isInstanceOf[StringType] || child.dataType == NullType) {
+ TypeCheckResult.TypeCheckSuccess
+ } else {
+ TypeCheckResult.TypeCheckFailure(s"unHex accepts String type, not ${child.dataType}")
+ }
+ }
+
+ override def eval(input: InternalRow): Any = {
+ val num = child.eval(input)
+ if (num == null) {
+ null
+ } else {
+ unhex(num.asInstanceOf[UTF8String].getBytes)
+ }
+ }
+
+ private val unhexDigits = {
+ val array = Array.fill[Byte](128)(-1)
+ (0 to 9).foreach(i => array('0' + i) = i.toByte)
+ (0 to 5).foreach(i => array('A' + i) = (i + 10).toByte)
+ (0 to 5).foreach(i => array('a' + i) = (i + 10).toByte)
+ array
+ }
+
+ private def unhex(inputBytes: Array[Byte]): Array[Byte] = {
+ var bytes = inputBytes
+ if ((bytes.length & 0x01) != 0) {
+ bytes = '0'.toByte +: bytes
+ }
+ val out = new Array[Byte](bytes.length >> 1)
+ // two characters form the hex value.
+ var i = 0
+ while (i < bytes.length) {
+ val first = unhexDigits(bytes(i))
+ val second = unhexDigits(bytes(i + 1))
+ if (first == -1 || second == -1) { return null}
+ out(i / 2) = (((first << 4) | second) & 0xFF).toByte
+ i += 2
+ }
+ out
+ }
+}
+
 case class Hypot(left: Expression, right: Expression)
  extends BinaryMathExpression(math.hypot, "HYPOT")
 

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

@@ -238,6 +238,12 @@ class MathFunctionsSuite extends SparkFunSuite with ExpressionEvalHelper {
  // scalastyle:on
  }
 
+ test("unhex") {
+ checkEvaluation(UnHex(Literal("737472696E67")), "string".getBytes)
+ checkEvaluation(UnHex(Literal("")), new Array[Byte](0))
+ checkEvaluation(UnHex(Literal("0")), Array[Byte](0))
+ }
+
  test("hypot") {
  testBinary(Hypot, math.hypot)
  }

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

@@ -1062,6 +1062,24 @@ object functions {
  */
  def hex(colName: String): Column = hex(Column(colName))
 
+ /**
+ * Inverse of hex. Interprets each pair of characters as a hexadecimal number
+ * and converts to the byte representation of number.
+ *
+ * @group math_funcs
+ * @since 1.5.0
+ */
+ def unhex(column: Column): Column = UnHex(column.expr)
+
+ /**
+ * Inverse of hex. Interprets each pair of characters as a hexadecimal number
+ * and converts to the byte representation of number.
+ *
+ * @group math_funcs
+ * @since 1.5.0
+ */
+ def unhex(colName: String): Column = unhex(Column(colName))
+
  /**
  * Computes `sqrt(a^2^ + b^2^)` without intermediate overflow or underflow.
  *

sql/core/src/test/scala/org/apache/spark/sql/MathExpressionsSuite.scala

@@ -225,6 +225,16 @@ class MathExpressionsSuite extends QueryTest {
  checkAnswer(data.selectExpr("hex(cast(d as binary))"), Seq(Row("68656C6C6F")))
  }
 
+ test("unhex") {
+ val data = Seq(("1C", "737472696E67")).toDF("a", "b")
+ checkAnswer(data.select(unhex('a)), Row(Array[Byte](28.toByte)))
+ checkAnswer(data.select(unhex('b)), Row("string".getBytes))
+ checkAnswer(data.selectExpr("unhex(a)"), Row(Array[Byte](28.toByte)))
+ checkAnswer(data.selectExpr("unhex(b)"), Row("string".getBytes))
+ checkAnswer(data.selectExpr("""unhex("##")"""), Row(null))
+ checkAnswer(data.selectExpr("""unhex("G123")"""), Row(null))
+ }
+
  test("hypot") {
  testTwoToOneMathFunction(hypot, hypot, math.hypot)
  }

sql/hive/compatibility/src/test/scala/org/apache/spark/sql/hive/execution/HiveCompatibilitySuite.scala

@@ -949,6 +949,7 @@ class HiveCompatibilitySuite extends HiveQueryFileTest with BeforeAndAfter {
  "udf_trim",
  "udf_ucase",
  "udf_unix_timestamp",
+ "udf_unhex",
  "udf_upper",
  "udf_var_pop",
  "udf_var_samp",