Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/5134#discussion_r29218551
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -115,6 +115,25 @@ object UnionPushdown extends Rule[LogicalPlan] {
*/
object ColumnPruning extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ // Eliminate unneeded attributes from Expand that is used in
GroupingSets
+ case a @ Aggregate(groupByExprs, aggregations, e @ Expand(projections,
output, child))
+ if (e.outputSet -- a.references).nonEmpty =>
+
+ val substitution = projections.map { groupExpr =>
--- End diff --
In `Analyzer.ResolveGroupingAnalytics`, the projections of `Expand` node
contain some `Literal`s that are constant null. Also the `groupingId` will be
replaced with concrete value (the bit mask). We need to keep these `Literal`s.
Because it performs `collect` on the `groupExpr: Seq[Expression]`, it just
keeps all `Literal`s and the `NamedExpression`s which are refered in `a:
Aggregate`.
So we do:
GroupExpression(a + 1, b, 1) => GroupExpression(a + 1, 1) # suppose
that b is not referred in above Aggregate
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