fix: Fix projection pushdown with literal joins (#16981)

crates/polars-plan/src/logical_plan/optimizer/projection_pushdown/joins.rs

@@ -19,10 +19,15 @@ fn add_keys_to_accumulated_state(
     // the JOIN executor
     if add_local {
         // take the left most name as output name
-        let name = aexpr_to_leaf_name(expr, expr_arena);
-        let node = expr_arena.add(AExpr::Column(name.clone()));
-        local_projection.push(ColumnNode(node));
-        Some(name)
+        let mut iter = aexpr_to_leaf_names_iter(expr, expr_arena);
+        if let Some(name) = iter.next() {
+            drop(iter);
+            let node = expr_arena.add(AExpr::Column(name.clone()));
+            local_projection.push(ColumnNode(node));
+            Some(name)
+        } else {
+            None
+        }
     } else {
         None
     }
@@ -250,15 +255,14 @@ pub(super) fn process_join(
                 continue;
             }
 
-            add_keys_to_accumulated_state(
+            let _ = add_keys_to_accumulated_state(
                 e.node(),
                 &mut pushdown_left,
                 &mut local_projection,
                 &mut names_left,
                 expr_arena,
                 true,
-            )
-            .unwrap();
+            );
         }
 
         // For left and innner joins we can set `coalesce` to `true` if the rhs key columns are not projected.

py-polars/tests/unit/operations/test_join.py

@@ -961,3 +961,12 @@ def test_join_raise_on_repeated_expression_key_names(coalesce: bool) -> None:
         left.join(
             right, on=[pl.col("a"), pl.col("a") % 2], how="full", coalesce=coalesce
         )
+
+
+def test_join_lit_panic_11410() -> None:
+    df = pl.LazyFrame({"date": [1, 2, 3], "symbol": [4, 5, 6]})
+    dates = df.select("date").unique(maintain_order=True)
+    symbols = df.select("symbol").unique(maintain_order=True)
+    assert symbols.join(dates, left_on=pl.lit(1), right_on=pl.lit(1)).drop(
+        "literal"
+    ).collect().to_dict(as_series=False) == {"symbol": [4], "date": [1]}