Github user marmbrus commented on the pull request:
https://github.com/apache/spark/pull/10311#issuecomment-164846751
Scala always puts the parameter names in the `scalasig` and you can get
them from the `Type` (which they describe how to get
[here](http://stackoverflow.com/questions/16724588/is-it-possible-to-get-the-typetag-of-a-runtime-instance))
```scala
def parameterNames: Seq[String] = {
import scala.reflect.runtime.universe._
val m = runtimeMirror(this.getClass.getClassLoader)
val classSymbol = m.staticClass(this.getClass.getName)
val t = classSymbol.selfType
val formalTypeArgs = t.typeSymbol.asClass.typeParams
val TypeRef(_, _, actualTypeArgs) = t
val constructorSymbol = t.member(nme.CONSTRUCTOR)
val params = if (constructorSymbol.isMethod) {
constructorSymbol.asMethod.paramss
} else {
// Find the primary constructor, and use its parameter ordering.
val primaryConstructorSymbol: Option[Symbol] =
constructorSymbol.asTerm.alternatives.find(
s => s.isMethod && s.asMethod.isPrimaryConstructor)
if (primaryConstructorSymbol.isEmpty) {
sys.error("Internal SQL error: Product object did not have a
primary constructor.")
} else {
primaryConstructorSymbol.get.asMethod.paramss
}
}
params.head.map(_.name.toString)
}
```
```scala
scala> sql("SELECT 1").queryExecution.logical.parameterNames
res1: Seq[String] = List(projectList, child)
```
Note thats just a quick draft and you could probably simplify it (or pull
this out into a utility since I think we do it in several places now).
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