cloud-fan commented on a change in pull request #33397:
URL: https://github.com/apache/spark/pull/33397#discussion_r672106833
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -647,6 +647,11 @@ object LimitPushDown extends Rule[LogicalPlan] {
// There is a Project between LocalLimit and Join if they do not have the
same output.
case LocalLimit(exp, project @ Project(_, join: Join)) =>
LocalLimit(exp, project.copy(child = pushLocalLimitThroughJoin(exp,
join)))
+ // Push down limit 1 through Aggregate if it is group only.
Review comment:
seems we can also turn Aggregate into Project in this case?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -647,6 +647,11 @@ object LimitPushDown extends Rule[LogicalPlan] {
// There is a Project between LocalLimit and Join if they do not have the
same output.
case LocalLimit(exp, project @ Project(_, join: Join)) =>
LocalLimit(exp, project.copy(child = pushLocalLimitThroughJoin(exp,
join)))
+ // Push down limit 1 through Aggregate if it is group only.
Review comment:
can we mention it in the comment?
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -647,6 +647,11 @@ object LimitPushDown extends Rule[LogicalPlan] {
// There is a Project between LocalLimit and Join if they do not have the
same output.
case LocalLimit(exp, project @ Project(_, join: Join)) =>
LocalLimit(exp, project.copy(child = pushLocalLimitThroughJoin(exp,
join)))
+ // Push down limit 1 and turn Aggregate into Project through Aggregate if
it is group only.
Review comment:
```suggestion
// Push down limit 1 through Aggregate and turn Aggregate into Project
if it is group only.
```
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