viirya commented on code in PR #37195:
URL: https://github.com/apache/spark/pull/37195#discussion_r923046512
##########
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/V2ScanRelationPushDown.scala:
##########
@@ -378,8 +406,12 @@ object V2ScanRelationPushDown extends Rule[LogicalPlan]
with PredicateHelper wit
}
(operation, isPushed && !isPartiallyPushed)
case s @ Sort(order, _, operation @ ScanOperation(project, filter,
sHolder: ScanBuilderHolder))
- if filter.isEmpty && CollapseProject.canCollapseExpressions(
- order, project, alwaysInline = true) =>
+ // Without building the Scan, we do not know the resulting column
names after aggregate
+ // push-down, and thus can't push down Top-N which needs to know the
ordering column names.
+ // TODO: we can support simple cases like GROUP BY columns directly
and ORDER BY the same
+ // columns, which we know the resulting column names: the
original table columns.
+ if sHolder.pushedAggregate.isEmpty && filter.isEmpty &&
+ CollapseProject.canCollapseExpressions(order, project, alwaysInline
= true) =>
Review Comment:
Hmm, is this regression? I.e. previously we can pushdown, but now we cannot?
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