Github user chenghao-intel commented on a diff in the pull request:
https://github.com/apache/spark/pull/6971#discussion_r33906234
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/misc.scala
---
@@ -47,4 +48,44 @@ case class Md5(child: Expression)
"org.apache.spark.unsafe.types.UTF8String.fromString" +
s"(org.apache.commons.codec.digest.DigestUtils.md5Hex($c))")
}
+
+}
+
+/**
+ * A function that returns a hash value of the argument
+ */
+case class Hash(children: Expression*) extends Expression {
+
+ override def foldable: Boolean = children.forall(_.foldable)
+ override def nullable: Boolean = children(0).nullable
+ override def dataType: DataType = IntegerType
+
+ override def eval(input: InternalRow): Any = {
+ val arglist = children.map(_.eval(input).asInstanceOf[AnyRef])
+ hashCode(arglist)
+ }
+
+ def hashCode(v: Any): Int = v match {
+ case null => 0
+ case arr: Array[_] => {
+ arr.foldLeft(0) { (acc, n) => acc + hashCode(n) }
+ }
+ case seq: Seq[_] => {
+ seq.foldLeft(0) { (acc, n) => acc + hashCode(n) }
+ }
+ case m: Map[_, _] => {
+ var res: Int = 0
+ m.foreach { case (k, v) => res += (hashCode(k) + hashCode(v)) }
+ res
+ }
+ case r: Row => {
+ var res: Int = 0
+ for (i <- 0 until r.length) {
+ res += 31 * res + hashCode(r.get(i))
+ }
+ res
+ }
+ case others => others.hashCode()
+ }
+
--- End diff --
Actually I am thinking if we need to add wrappers for ALL of the internal
data type, which hide the details for the expression developers. e.g the
hashCode, serialization / deseriazliation, equality etc. Currently seems the
expression developers needs to keep eyes on those details.
Any ideas?
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