viirya commented on code in PR #44429:
URL: https://github.com/apache/spark/pull/44429#discussion_r1433407429
##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala:
##########
@@ -1602,12 +1595,6 @@ object EliminateSorts extends Rule[LogicalPlan] {
plan match {
case Sort(_, global, child) if canRemoveGlobalSort || !global =>
recursiveRemoveSort(child, canRemoveGlobalSort)
- case Sort(sortOrder, true, child) =>
- // For this case, the upper sort is local so the ordering of present
sort is unnecessary,
- // so here we only preserve its output partitioning using
`RepartitionByExpression`.
- // We should use `None` as the optNumPartitions so AQE can coalesce
shuffle partitions.
- // This behavior is same with original global sort.
- RepartitionByExpression(sortOrder, recursiveRemoveSort(child, true),
None)
Review Comment:
Said there are Sorts like
```
- Sort (local)
- Sort (global)
- Sort (local)
```
We reach:
```scala
case s @ Sort(_, global, child) => s.copy(child = recursiveRemoveSort(child,
global))
```
Previously we can get rid of the middle global Sort and the bottom local
Sort by `RepartitionByExpression(sortOrder, recursiveRemoveSort(child, true),
None)` and:
```scala
case Sort(_, global, child) if canRemoveGlobalSort || !global =>
recursiveRemoveSort(child, canRemoveGlobalSort)
```
How does `EliminateSorts` still do it?
The code you point is same (not changed in this PR):
```scala
case s @ Sort(_, global, child) => s.copy(child = recursiveRemoveSort(child,
global))
```
But in `recursiveRemoveSort`, as `canRemoveGlobalSort` is false, we don't
get rid of the middle global Sort now (it will be done in
`RemoveRedundantSorts` now).
Do I miss ore misread something?
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