Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/20024#discussion_r159628763
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala
---
@@ -199,13 +199,60 @@ case class Cast(child: Expression, dataType:
DataType, timeZoneId: Option[String
// [[func]] assumes the input is no longer null because eval already
does the null check.
@inline private[this] def buildCast[T](a: Any, func: T => Any): Any =
func(a.asInstanceOf[T])
+ @inline private[this] def buildWriter[T](
+ a: Any, buffer: UTF8StringBuilder, writer: (T, UTF8StringBuilder) =>
Unit): Unit = {
+ writer(a.asInstanceOf[T], buffer)
+ }
+
+ private[this] def buildElemWriter(
+ from: DataType): (Any, UTF8StringBuilder) => Unit = from match {
+ case BinaryType => buildWriter[Array[Byte]](_, _, (b, buf) =>
buf.append(b))
+ case StringType => buildWriter[UTF8String](_, _, (b, buf) =>
buf.append(b))
+ case DateType => buildWriter[Int](_, _,
+ (d, buf) => buf.append(DateTimeUtils.dateToString(d)))
+ case TimestampType => buildWriter[Long](_, _,
+ (t, buf) => buf.append(DateTimeUtils.timestampToString(t)))
+ case ar: ArrayType =>
+ buildWriter[ArrayData](_, _, (array, buf) => {
+ buf.append("[")
+ if (array.numElements > 0) {
+ val writeElemToBuffer = buildElemWriter(ar.elementType)
+ writeElemToBuffer(array.get(0, ar.elementType), buf)
+ var i = 1
+ while (i < array.numElements) {
+ buf.append(", ")
+ writeElemToBuffer(array.get(i, ar.elementType), buf)
+ i += 1
+ }
+ }
+ buf.append("]")
+ })
+ case _ => buildWriter[Any](_, _, (o, buf) =>
buf.append(String.valueOf(o)))
+ }
// UDFToString
private[this] def castToString(from: DataType): Any => Any = from match {
case BinaryType => buildCast[Array[Byte]](_, UTF8String.fromBytes)
case DateType => buildCast[Int](_, d =>
UTF8String.fromString(DateTimeUtils.dateToString(d)))
case TimestampType => buildCast[Long](_,
t => UTF8String.fromString(DateTimeUtils.timestampToString(t,
timeZone)))
+ case ar: ArrayType =>
+ buildCast[ArrayData](_, array => {
+ val res = new UTF8StringBuilder
+ res.append("[")
+ if (array.numElements > 0) {
+ val writeElemToBuffer = buildElemWriter(ar.elementType)
+ writeElemToBuffer(array.get(0, ar.elementType), res)
--- End diff --
I don't get it, why do we need the `buildElemWriter`? I think it's as
simple as
```
val toUTF8String = castToString(et)
builder.append(toUTF8String(array.get(0, et)).asInstanceOf[UTF8String])
var i = 1
while ...
```
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