Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/11177#discussion_r52700130
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/Expand.scala ---
@@ -71,9 +80,76 @@ case class Expand(
idx = 0
}
+ numOutputRows += 1
result
}
}
}
}
+
+ override def upstream(): RDD[InternalRow] = {
+ child.asInstanceOf[CodegenSupport].upstream()
+ }
+
+ protected override def doProduce(ctx: CodegenContext): String = {
+ child.asInstanceOf[CodegenSupport].produce(ctx, this)
+ }
+
+ override def doConsume(ctx: CodegenContext, input: Seq[ExprCode]):
String = {
+ val uniqExprs: IndexedSeq[Set[Expression]] = output.indices.map { i =>
+ projections.map(p => p(i)).toSet
+ }
+
+ ctx.currentVars = input
+ val resultVars = uniqExprs.zipWithIndex.map { case (exprs, i) =>
+ val expr = exprs.head
+ if (exprs.size == 1) {
+ // it's common to have same expression for some columns in all the
projections, for example,
+ // GroupingSet will copy all the output from child as the first
part of output.
+ // We should only generate the columns once.
+ BindReferences.bindReference(expr, child.output).gen(ctx)
+ } else {
+ val isNull = ctx.freshName("isNull")
+ val value = ctx.freshName("value")
+ val code =
+ s"""
+ |boolean $isNull = true;
+ |${ctx.javaType(expr.dataType)} $value =
${ctx.defaultValue(expr.dataType)};
+ """.stripMargin
+ ExprCode(code, isNull, value)
+ }
+ }
+
+ // In order to prevent code exploration, we can't call `consume()`
many times, so we call
+ // that in a loop, and use swith/case to select the projections.
+ val projectCodes = projections.zipWithIndex.map { case (exprs, i) =>
--- End diff --
i find the body of this loop pretty hard to understand. can we add some
high level comment to explain what's going on?
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