SubhamSinghal commented on code in PR #21621:
URL: https://github.com/apache/datafusion/pull/21621#discussion_r3986864957
##########
datafusion/optimizer/src/push_down_limit.rs:
##########
@@ -29,6 +29,9 @@ use datafusion_common::utils::combine_limit;
use datafusion_expr::logical_plan::{Join, JoinType, Limit, LogicalPlan};
use datafusion_expr::{FetchType, SkipType, lit};
+mod topk_through_join;
+use topk_through_join::push_topk_through_join;
+
/// Optimization rule that tries to push down `LIMIT`.
Review Comment:
Addressed in 8dbc1dd53034ec22e39c20a515f54f1addf60cc1
##########
datafusion/optimizer/src/push_down_limit.rs:
##########
@@ -47,146 +50,159 @@ impl OptimizerRule for PushDownLimit {
true
}
- #[expect(clippy::only_used_in_recursion)]
fn rewrite(
&self,
plan: LogicalPlan,
config: &dyn OptimizerConfig,
) -> Result<Transformed<LogicalPlan>> {
- let LogicalPlan::Limit(mut limit) = plan else {
- return Ok(Transformed::no(plan));
- };
+ match plan {
+ LogicalPlan::Limit(limit) => rewrite_limit(limit, config),
+ LogicalPlan::Sort(s) if s.fetch.is_some() => {
+ push_topk_through_join(LogicalPlan::Sort(s))
+ }
+ other => Ok(Transformed::no(other)),
+ }
+ }
- // Currently only rewrite if skip and fetch are both literals
- let SkipType::Literal(skip) = limit.get_skip_type()? else {
+ fn name(&self) -> &str {
+ "push_down_limit"
+ }
+
+ fn apply_order(&self) -> Option<ApplyOrder> {
+ Some(ApplyOrder::TopDown)
+ }
+}
+
+/// Limit-side dispatch (split out from `rewrite` so that the top-level
+/// match in `OptimizerRule::rewrite` reads as a parallel branch alongside
+/// the Sort-with-fetch handler).
+#[expect(clippy::only_used_in_recursion)]
Review Comment:
Addressed in
https://github.com/apache/datafusion/commit/8dbc1dd53034ec22e39c20a515f54f1addf60cc1
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