datafusion_python/expr/
empty_relation.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use std::fmt::{self, Display, Formatter};
19
20use datafusion::logical_expr::EmptyRelation;
21use pyo3::prelude::*;
22use pyo3::IntoPyObjectExt;
23
24use super::logical_node::LogicalNode;
25use crate::common::df_schema::PyDFSchema;
26use crate::sql::logical::PyLogicalPlan;
27
28#[pyclass(frozen, name = "EmptyRelation", module = "datafusion.expr", subclass)]
29#[derive(Clone)]
30pub struct PyEmptyRelation {
31    empty: EmptyRelation,
32}
33
34impl From<PyEmptyRelation> for EmptyRelation {
35    fn from(empty_relation: PyEmptyRelation) -> Self {
36        empty_relation.empty
37    }
38}
39
40impl From<EmptyRelation> for PyEmptyRelation {
41    fn from(empty: EmptyRelation) -> PyEmptyRelation {
42        PyEmptyRelation { empty }
43    }
44}
45
46impl Display for PyEmptyRelation {
47    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
48        write!(
49            f,
50            "Empty Relation
51            Produce One Row: {:?}
52            Schema: {:?}",
53            &self.empty.produce_one_row, &self.empty.schema
54        )
55    }
56}
57
58#[pymethods]
59impl PyEmptyRelation {
60    fn produce_one_row(&self) -> PyResult<bool> {
61        Ok(self.empty.produce_one_row)
62    }
63
64    /// Resulting Schema for this `EmptyRelation` node instance
65    fn schema(&self) -> PyResult<PyDFSchema> {
66        Ok((*self.empty.schema).clone().into())
67    }
68
69    /// Get a String representation of this column
70    fn __repr__(&self) -> String {
71        format!("{self}")
72    }
73
74    fn __name__(&self) -> PyResult<String> {
75        Ok("EmptyRelation".to_string())
76    }
77}
78
79impl LogicalNode for PyEmptyRelation {
80    fn inputs(&self) -> Vec<PyLogicalPlan> {
81        // table scans are leaf nodes and do not have inputs
82        vec![]
83    }
84
85    fn to_variant<'py>(&self, py: Python<'py>) -> PyResult<Bound<'py, PyAny>> {
86        self.clone().into_bound_py_any(py)
87    }
88}
datafusion_python/expr/empty_relation.rs

datafusion_python/expr/
empty_relation.rs
