refactor: Small drive-by's (#20772)

Author: ritchie46

crates/polars-plan/src/plans/aexpr/mod.rs

@@ -47,6 +47,7 @@ pub enum IRAggExpr {
         method: QuantileMethod,
     },
     Sum(Node),
+    // include_nulls
     Count(Node, bool),
     Std(Node, u8),
     Var(Node, u8),

crates/polars-plan/src/plans/aexpr/traverse.rs

@@ -3,7 +3,7 @@ use super::*;
 impl AExpr {
     /// Push the inputs of this node to the given container, in reverse order.
     /// This ensures the primary node responsible for the name is pushed last.
-    pub(crate) fn inputs_rev<E>(&self, container: &mut E)
+    pub fn inputs_rev<E>(&self, container: &mut E)
     where
         E: Extend<Node>,
     {

crates/polars-stream/src/physical_plan/lower_group_by.rs

@@ -12,6 +12,7 @@ use polars_plan::prelude::GroupbyOptions;
 use polars_utils::arena::{Arena, Node};
 use polars_utils::itertools::Itertools;
 use polars_utils::pl_str::PlSmallStr;
+use recursive::recursive;
 use slotmap::SlotMap;
 
 use super::lower_expr::lower_exprs;
@@ -71,6 +72,7 @@ fn build_group_by_fallback(
 ///
 /// Such an expression is defined as the elementwise combination of scalar
 /// aggregations of elementwise combinations of the input columns / scalar literals.
+#[recursive]
 fn try_lower_elementwise_scalar_agg_expr(
     expr: Node,
     inside_agg: bool,
@@ -178,7 +180,10 @@ fn try_lower_elementwise_scalar_agg_expr(
         },
 
         AExpr::Agg(agg) => {
-            let orig_agg = agg.clone();
+            // Nested aggregates not supported.
+            if inside_agg {
+                return None;
+            }
             match agg {
                 IRAggExpr::Min { input, .. }
                 | IRAggExpr::Max { input, .. }
@@ -188,10 +193,7 @@ fn try_lower_elementwise_scalar_agg_expr(
                 | IRAggExpr::Sum(input)
                 | IRAggExpr::Var(input, ..)
                 | IRAggExpr::Std(input, ..) => {
-                    // Nested aggregates not supported.
-                    if inside_agg {
-                        return None;
-                    }
+                    let orig_agg = agg.clone();
                     // Lower and replace input.
                     let trans_input = lower_rec!(*input, true)?;
                     let mut trans_agg = orig_agg;
@@ -311,7 +313,8 @@ fn try_build_streaming_group_by(
             &mut trans_agg_exprs,
             &trans_input_cols,
         )?;
-        trans_output_exprs.push(ExprIR::new(trans_node, agg.output_name_inner().clone()));
+        let output_name = OutputName::Alias(agg.output_name().clone());
+        trans_output_exprs.push(ExprIR::new(trans_node, output_name));
     }
 
     let input_schema = &phys_sm[trans_input.node].output_schema;