Fix Polars expr pushdown

duckdb/polars_io.py

@@ -1,5 +1,6 @@
 from __future__ import annotations  # noqa: D100
 
+import contextlib
 import datetime
 import json
 import typing
@@ -176,9 +177,12 @@ def _pl_tree_to_sql(tree: _ExpressionTree) -> str:
         if dtype.startswith("{'Decimal'") or dtype == "Decimal":
             decimal_value = value["Decimal"]
             assert isinstance(decimal_value, list), (
-                f"A {dtype} should be a two member list but got {type(decimal_value)}"
+                f"A {dtype} should be a two or three member list but got {type(decimal_value)}"
             )
-            return str(Decimal(decimal_value[0]) / Decimal(10 ** decimal_value[1]))
+            assert 2 <= len(decimal_value) <= 3, (
+                f"A {dtype} should be a two or three member list but got {len(decimal_value)} member list"
+            )
+            return str(Decimal(decimal_value[0]) / Decimal(10 ** decimal_value[-1]))
 
         # Datetime with microseconds since epoch
         if dtype.startswith("{'Datetime'") or dtype == "Datetime":
@@ -260,7 +264,8 @@ def source_generator(
             relation_final = relation_final.limit(n_rows)
         if predicate is not None:
             # We have a predicate, if possible, we push it down to DuckDB
-            duck_predicate = _predicate_to_expression(predicate)
+            with contextlib.suppress(AssertionError, KeyError):
+                duck_predicate = _predicate_to_expression(predicate)
         # Try to pushdown filter, if one exists
         if duck_predicate is not None:
             relation_final = relation_final.filter(duck_predicate)

tests/fast/arrow/test_polars.py

@@ -1,4 +1,5 @@
 import datetime
+import json
 
 import pytest
 
@@ -8,7 +9,7 @@
 arrow = pytest.importorskip("pyarrow")
 pl_testing = pytest.importorskip("polars.testing")
 
-from duckdb.polars_io import _predicate_to_expression  # noqa: E402
+from duckdb.polars_io import _pl_tree_to_sql, _predicate_to_expression  # noqa: E402
 
 
 def valid_filter(filter):
@@ -175,7 +176,7 @@ def test_polars_column_with_tricky_name(self, duckdb_cursor):
             "UBIGINT",
             "FLOAT",
             "DOUBLE",
-            # "HUGEINT",
+            "HUGEINT",
             "DECIMAL(4,1)",
             "DECIMAL(9,1)",
             "DECIMAL(18,4)",
@@ -605,3 +606,50 @@ def test_polars_lazy_many_batches(self, duckdb_cursor):
         correct = duckdb_cursor.execute("FROM t").fetchall()
 
         assert res == correct
+
+    def test_invalid_expr_json(self):
+        bad_key_expr = """
+        {
+            "BinaryExpr": {
+                "left": { "Column": "foo" },
+                "middle": "Gt",
+                "right": { "Literal": { "Int": 5 } }
+            }
+        }
+        """
+        with pytest.raises(KeyError, match="'op'"):
+            _pl_tree_to_sql(json.loads(bad_key_expr))
+
+        bad_type_expr = """
+        {
+            "BinaryExpr": {
+                "left": { "Column": [ "foo" ]  },
+                "op": "Gt",
+                "right": { "Literal": { "Int": 5 } }
+            }
+        }
+        """
+        with pytest.raises(AssertionError, match="The col name of a Column should be a str but got"):
+            _pl_tree_to_sql(json.loads(bad_type_expr))
+
+    def test_decimal_scale(self):
+        scalar_decimal_no_scale = """
+          { "Scalar": {
+            "Decimal": [
+              1,
+              0
+            ]
+          } }
+        """
+        assert _pl_tree_to_sql(json.loads(scalar_decimal_no_scale)) == "1"
+
+        scalar_decimal_scale = """
+          { "Scalar": {
+            "Decimal": [
+              1,
+              38,
+              0
+            ]
+          } }
+        """
+        assert _pl_tree_to_sql(json.loads(scalar_decimal_scale)) == "1"