fix: Fix filter incorrectly pushed past struct unnest when unnested c…

…olumn name matches upper column name (pola-rs#19638)

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

@@ -576,6 +576,28 @@ impl<'a> PredicatePushDown<'a> {
                                 expr_arena,
                             ))
                         },
+                        FunctionIR::Unnest { columns } => {
+                            let exclude = columns.iter().cloned().collect::<PlHashSet<_>>();
+
+                            let local_predicates =
+                                transfer_to_local_by_name(expr_arena, &mut acc_predicates, |x| {
+                                    exclude.contains(x)
+                                });
+
+                            let lp = self.pushdown_and_continue(
+                                lp,
+                                acc_predicates,
+                                lp_arena,
+                                expr_arena,
+                                false,
+                            )?;
+                            Ok(self.optional_apply_predicate(
+                                lp,
+                                local_predicates,
+                                lp_arena,
+                                expr_arena,
+                            ))
+                        },
                         _ => self.pushdown_and_continue(
                             lp,
                             acc_predicates,

py-polars/tests/unit/test_predicates.py

@@ -511,3 +511,45 @@ def test_predicate_push_down_list_gather_17492() -> None:
         .filter(pl.col("val").list.get(1, null_on_oob=True) == 1)
         .explain()
     )
+
+
+def test_predicate_pushdown_struct_unnest_19632() -> None:
+    lf = pl.LazyFrame({"a": [{"a": 1, "b": 2}]}).unnest("a")
+
+    q = lf.filter(pl.col("a") == 1)
+    plan = q.explain()
+
+    assert "FILTER" in plan
+    assert plan.index("FILTER") < plan.index("UNNEST")
+
+    assert_frame_equal(
+        q.collect(),
+        pl.DataFrame({"a": 1, "b": 2}),
+    )
+
+    # With `pl.struct()`
+    lf = pl.LazyFrame({"a": 1, "b": 2}).select(pl.struct(pl.all())).unnest("a")
+
+    q = lf.filter(pl.col("a") == 1)
+    plan = q.explain()
+
+    assert "FILTER" in plan
+    assert plan.index("FILTER") < plan.index("UNNEST")
+
+    assert_frame_equal(
+        q.collect(),
+        pl.DataFrame({"a": 1, "b": 2}),
+    )
+
+    # With `value_counts()`
+    lf = pl.LazyFrame({"a": [1]}).select(pl.col("a").value_counts()).unnest("a")
+
+    q = lf.filter(pl.col("a") == 1)
+    plan = q.explain()
+
+    assert plan.index("FILTER") < plan.index("UNNEST")
+
+    assert_frame_equal(
+        q.collect(),
+        pl.DataFrame({"a": 1, "count": 1}, schema={"a": pl.Int64, "count": pl.UInt32}),
+    )