feat(polars): support pyarrow decimal types

ibis/backends/polars/__init__.py

@@ -336,13 +336,9 @@ def _to_pyarrow_table(
             df = lf.collect()
 
         table = df.to_arrow()
-        if isinstance(expr, ir.Table):
-            schema = expr.schema().to_pyarrow()
-            return table.cast(schema)
-        elif isinstance(expr, ir.Value):
-            schema = sch.schema({expr.get_name(): expr.type().to_pyarrow()})
-            schema = schema.to_pyarrow()
-            return table.cast(schema)
+        if isinstance(expr, (ir.Table, ir.Value)):
+            schema = expr.as_table().schema().to_pyarrow()
+            return table.rename_columns(schema.names).cast(schema)
         else:
             raise com.IbisError(f"Cannot execute expression of type: {type(expr)}")
 

ibis/backends/polars/datatypes.py

@@ -39,6 +39,11 @@ def to_polars_type(dtype):
         raise NotImplementedError(f"Unsupported type: {dtype!r}")
 
 
+@to_polars_type.register(dt.Decimal)
+def from_ibis_decimal(dtype):
+    return pl.Decimal(dtype.precision, dtype.scale)
+
+
 @to_polars_type.register(dt.Timestamp)
 def from_ibis_timestamp(dtype):
     return pl.Datetime("ns", dtype.timezone)
@@ -103,6 +108,11 @@ def from_polars_struct(typ):
     )
 
 
+@to_ibis_dtype.register(pl.Decimal)
+def from_polars_decimal(typ: pl.Decimal):
+    return dt.Decimal(precision=typ.precision, scale=typ.scale)
+
+
 @sch.infer.register(pl.LazyFrame)
 def from_polars_schema(df: pl.LazyFrame) -> sch.Schema:
     fields = [(name, to_ibis_dtype(typ)) for name, typ in df.schema.items()]

ibis/backends/tests/test_numeric.py

@@ -591,7 +591,9 @@ def test_numeric_literal(con, backend, expr, expected_types):
     ],
 )
 @pytest.mark.notimpl(
-    ['polars', 'datafusion'], "Unsupported type", raises=NotImplementedError
+    ['polars', 'datafusion'],
+    "Unsupported type",
+    raises=(NotImplementedError, ValueError),
 )
 def test_decimal_literal(con, backend, expr, expected_types, expected_result):
     backend_name = backend.name()