fix: Fix incorrect result from inequality filter after join on LazyFr…

…ame (#19898)

crates/polars-plan/src/plans/optimizer/predicate_pushdown/join.rs

@@ -44,25 +44,25 @@ fn should_block_join_specific(
         // any operation that checks for equality or ordering can be wrong because
         // the join can produce null values
         // TODO! check if we can be less conservative here
-        BinaryExpr { op, left, right } => match op {
-            Operator::NotEq => LeftRight(false, false),
-            Operator::Eq => {
-                let LeftRight(bleft, bright) = join_produces_null(how);
+        BinaryExpr {
+            op: Operator::Eq | Operator::NotEq,
+            left,
+            right,
+        } => {
+            let LeftRight(bleft, bright) = join_produces_null(how);
 
-                let l_name = aexpr_output_name(*left, expr_arena).unwrap();
-                let r_name = aexpr_output_name(*right, expr_arena).unwrap();
+            let l_name = aexpr_output_name(*left, expr_arena).unwrap();
+            let r_name = aexpr_output_name(*right, expr_arena).unwrap();
 
-                let is_in_on = on_names.contains(&l_name) || on_names.contains(&r_name);
+            let is_in_on = on_names.contains(&l_name) || on_names.contains(&r_name);
 
-                let block_left =
-                    is_in_on && (schema_left.contains(&l_name) || schema_left.contains(&r_name));
-                let block_right =
-                    is_in_on && (schema_right.contains(&l_name) || schema_right.contains(&r_name));
-                LeftRight(block_left | bleft, block_right | bright)
-            },
-            _ => join_produces_null(how),
+            let block_left =
+                is_in_on && (schema_left.contains(&l_name) || schema_left.contains(&r_name));
+            let block_right =
+                is_in_on && (schema_right.contains(&l_name) || schema_right.contains(&r_name));
+            LeftRight(block_left | bleft, block_right | bright)
         },
-        _ => LeftRight(false, false),
+        _ => join_produces_null(how),
     }
 }
 

py-polars/tests/unit/test_predicates.py

@@ -555,16 +555,41 @@ def test_predicate_pushdown_struct_unnest_19632() -> None:
     )
 
 
-def test_predicate_pushdown_right_join_19772() -> None:
-    left = pl.LazyFrame({"k": [1], "v": [7]})
-    right = pl.LazyFrame({"k": [1, 2]})
+@pytest.mark.parametrize(
+    "predicate",
+    [
+        pl.col("v") == 7,
+        pl.col("v") != 99,
+        pl.col("v") > 0,
+        pl.col("v") < 999,
+        pl.col("v").is_in([7]),
+        pl.col("v").cast(pl.Boolean),
+        pl.col("b"),
+    ],
+)
+@pytest.mark.parametrize("alias", [True, False])
+@pytest.mark.parametrize("join_type", ["left", "right"])
+def test_predicate_pushdown_join_19772(
+    predicate: pl.Expr, join_type: str, alias: bool
+) -> None:
+    left = pl.LazyFrame({"k": [1, 2]})
+    right = pl.LazyFrame({"k": [1], "v": [7], "b": True})
+
+    if join_type == "right":
+        [left, right] = [right, left]
 
-    q = left.join(right, on="k", how="right").filter(pl.col("v") == 7)
+    if alias:
+        predicate = predicate.alias(":V")
+
+    q = left.join(right, on="k", how=join_type).filter(predicate)  # type: ignore[arg-type]
 
     plan = q.explain()
     assert plan.startswith("FILTER")
 
-    expect = pl.DataFrame({"v": 7, "k": 1})
+    expect = pl.DataFrame({"k": 1, "v": 7, "b": True})
+
+    if join_type == "right":
+        expect = expect.select("v", "b", "k")
 
     assert_frame_equal(q.collect(no_optimization=True), expect)
     assert_frame_equal(q.collect(), expect)