From 77922c990f464416ab90970cd8bb5e369acd7511 Mon Sep 17 00:00:00 2001
From: ritchie <ritchie46@gmail.com>
Date: Mon, 9 Sep 2024 13:53:21 +0200
Subject: [PATCH] wip: [skip ci]

---
 .../src/executors/projection.rs               |  4 ++--
 .../src/executors/projection_utils.rs         | 19 ++++++++++++-------
 crates/polars-plan/src/plans/aexpr/mod.rs     |  1 +
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/crates/polars-mem-engine/src/executors/projection.rs b/crates/polars-mem-engine/src/executors/projection.rs
index 43ffdd98c753..0f1ee259dc57 100644
--- a/crates/polars-mem-engine/src/executors/projection.rs
+++ b/crates/polars-mem-engine/src/executors/projection.rs
@@ -37,7 +37,7 @@ impl ProjectionExec {
                     self.has_windows,
                     self.options.run_parallel,
                 )?;
-                check_expand_literals(selected_cols, df.is_empty(), self.options)
+                check_expand_literals(&self.expr, selected_cols, df.is_empty(), self.options)
             });
 
             let df = POOL.install(|| iter.collect::<PolarsResult<Vec<_>>>())?;
@@ -53,7 +53,7 @@ impl ProjectionExec {
                 self.has_windows,
                 self.options.run_parallel,
             )?;
-            check_expand_literals(selected_cols, df.is_empty(), self.options)?
+            check_expand_literals(&self.expr, selected_cols, df.is_empty(), self.options)?
         };
 
         // this only runs during testing and check if the runtime type matches the predicted schema
diff --git a/crates/polars-mem-engine/src/executors/projection_utils.rs b/crates/polars-mem-engine/src/executors/projection_utils.rs
index 979c29321cb9..cd41e9260c92 100644
--- a/crates/polars-mem-engine/src/executors/projection_utils.rs
+++ b/crates/polars-mem-engine/src/executors/projection_utils.rs
@@ -243,6 +243,7 @@ pub(super) fn evaluate_physical_expressions(
 }
 
 pub(super) fn check_expand_literals(
+    phys_expr: &[Arc<dyn PhysicalExpr>],
     mut selected_columns: Vec<Series>,
     zero_length: bool,
     options: ProjectionOptions,
@@ -282,21 +283,25 @@ pub(super) fn check_expand_literals(
     if !all_equal_len && should_broadcast {
         selected_columns = selected_columns
             .into_iter()
-            .map(|series| {
+            .zip(phys_expr)
+            .map(|(series, phys)| {
                 Ok(match series.len() {
                     0 if df_height == 1 => series,
                     1 => {
                         if has_empty {
-
-                        polars_ensure!(df_height == 1,
-                        ComputeError: "Series length {} doesn't match the DataFrame height of {}",
-                        series.len(), df_height
-                    );
-
+                            polars_ensure!(df_height == 1,
+                                ComputeError: "Series length {} doesn't match the DataFrame height of {}",
+                                series.len(), df_height
+                            );
                             series.slice(0, 0)
                         } else if df_height == 1 {
                             series
                         } else {
+                            polars_ensure!(phys.is_scalar(),
+                                InvalidOperation: "Series length {} doesn't match the DataFrame height of {}\n\n\
+                                If you want this Series to be broadcasted, ensure it is a scalar (for instance by adding '.first()'.",
+                                series.len(), df_height
+                            );
                             series.new_from_index(0, df_height)
                         }
                     },
diff --git a/crates/polars-plan/src/plans/aexpr/mod.rs b/crates/polars-plan/src/plans/aexpr/mod.rs
index 10ccc393a9d9..b13f06a3e523 100644
--- a/crates/polars-plan/src/plans/aexpr/mod.rs
+++ b/crates/polars-plan/src/plans/aexpr/mod.rs
@@ -22,6 +22,7 @@ use crate::constants::LEN;
 use crate::plans::Context;
 use crate::prelude::*;
 pub use scalar::is_scalar_ae;
+pub use traverse::*;
 
 #[derive(Clone, Debug, IntoStaticStr)]
 #[cfg_attr(feature = "ir_serde", derive(Serialize, Deserialize))]