Add Python wrapper for LogicalPlan::Filter (#192)

* Add Python wrapper for LogicalPlan::Filter

* clippy

* clippy

* Update src/expr/filter.rs

Co-authored-by: Liang-Chi Hsieh <[email protected]>

---------

Co-authored-by: Liang-Chi Hsieh <[email protected]>

datafusion/tests/test_imports.py

@@ -35,6 +35,7 @@
     Expr,
     Projection,
     TableScan,
+    Filter,
     Limit,
     Aggregate,
     Sort,
@@ -58,7 +59,7 @@ def test_class_module_is_datafusion():
     ]:
         assert klass.__module__ == "datafusion"
 
-    for klass in [Expr, Projection, TableScan, Aggregate, Sort, Limit]:
+    for klass in [Expr, Projection, TableScan, Aggregate, Sort, Limit, Filter]:
         assert klass.__module__ == "datafusion.expr"
 
     for klass in [DFField, DFSchema]:

src/expr.rs

@@ -25,6 +25,7 @@ use datafusion_expr::{col, lit, Cast, Expr, GetIndexedField};
 use datafusion::scalar::ScalarValue;
 
 pub mod aggregate;
+pub mod filter;
 pub mod limit;
 pub mod logical_node;
 pub mod projection;
@@ -146,6 +147,7 @@ pub(crate) fn init_module(m: &PyModule) -> PyResult<()> {
     m.add_class::<PyExpr>()?;
     m.add_class::<table_scan::PyTableScan>()?;
     m.add_class::<projection::PyProjection>()?;
+    m.add_class::<filter::PyFilter>()?;
     m.add_class::<limit::PyLimit>()?;
     m.add_class::<aggregate::PyAggregate>()?;
     m.add_class::<sort::PySort>()?;

src/expr/filter.rs

@@ -0,0 +1,83 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use datafusion_expr::logical_plan::Filter;
+use pyo3::prelude::*;
+use std::fmt::{self, Display, Formatter};
+
+use crate::common::df_schema::PyDFSchema;
+use crate::expr::logical_node::LogicalNode;
+use crate::expr::PyExpr;
+use crate::sql::logical::PyLogicalPlan;
+
+#[pyclass(name = "Filter", module = "datafusion.expr", subclass)]
+#[derive(Clone)]
+pub struct PyFilter {
+    filter: Filter,
+}
+
+impl From<Filter> for PyFilter {
+    fn from(filter: Filter) -> PyFilter {
+        PyFilter { filter }
+    }
+}
+
+impl From<PyFilter> for Filter {
+    fn from(filter: PyFilter) -> Self {
+        filter.filter
+    }
+}
+
+impl Display for PyFilter {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Filter
+            \nPredicate: {:?}
+            \nInput: {:?}",
+            &self.filter.predicate, &self.filter.input
+        )
+    }
+}
+
+#[pymethods]
+impl PyFilter {
+    /// Retrieves the predicate expression for this `Filter`
+    fn predicate(&self) -> PyExpr {
+        PyExpr::from(self.filter.predicate.clone())
+    }
+
+    /// Retrieves the input `LogicalPlan` to this `Filter` node
+    fn input(&self) -> PyLogicalPlan {
+        PyLogicalPlan::from((*self.filter.input).clone())
+    }
+
+    /// Resulting Schema for this `Filter` node instance
+    fn schema(&self) -> PyDFSchema {
+        self.filter.input.schema().as_ref().clone().into()
+    }
+
+    fn __repr__(&self) -> String {
+        format!("Filter({})", self)
+    }
+}
+
+impl LogicalNode for PyFilter {
+    fn input(&self) -> Vec<PyLogicalPlan> {
+        vec![PyLogicalPlan::from((*self.filter.input).clone())]
+    }
+}