Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/7181#discussion_r33752809
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/math.scala
---
@@ -303,6 +295,66 @@ case class Hex(child: Expression) extends
UnaryExpression with Serializable {
}
}
+/**
+ * Performs the inverse operation of HEX.
+ * Resulting characters are returned as a byte array.
+ */
+case class Unhex(child: Expression)
+ extends UnaryExpression with AutoCastInputTypes with Serializable {
+
+ override def nullable: Boolean = true
+ override def dataType: DataType = BinaryType
+ override def inputTypes: Seq[DataType] = Seq(BinaryType)
+
+ override def eval(input: InternalRow): Any = {
+ val num = child.eval(input)
+ if (num == null) {
+ null
+ } else {
+ unhex(num.asInstanceOf[UTF8String].getBytes)
+ }
+ }
+
+ // lookup table to translate '0' -> 0 ... 'F'/'f' -> 15
+ private[this] val unhexDigits = {
--- End diff --
Less code is better than more code. From performance's point of view, there
is never an end to stop optimize it. I think we could go with something that's
good enough (won't be the bottle neck).
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