datafusion_physical_expr/expressions/
literal.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
18//! Literal expressions for physical operations
19
20use std::any::Any;
21use std::hash::Hash;
22use std::sync::Arc;
23
24use crate::physical_expr::PhysicalExpr;
25
26use arrow::datatypes::{Field, FieldRef};
27use arrow::{
28    datatypes::{DataType, Schema},
29    record_batch::RecordBatch,
30};
31use datafusion_common::{Result, ScalarValue};
32use datafusion_expr::expr::FieldMetadata;
33use datafusion_expr::Expr;
34use datafusion_expr_common::columnar_value::ColumnarValue;
35use datafusion_expr_common::interval_arithmetic::Interval;
36use datafusion_expr_common::sort_properties::{ExprProperties, SortProperties};
37
38/// Represents a literal value
39#[derive(Debug, PartialEq, Eq, Clone)]
40pub struct Literal {
41    value: ScalarValue,
42    field: FieldRef,
43}
44
45impl Hash for Literal {
46    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
47        self.value.hash(state);
48        let metadata = self.field.metadata();
49        let mut keys = metadata.keys().collect::<Vec<_>>();
50        keys.sort();
51        for key in keys {
52            key.hash(state);
53            metadata.get(key).unwrap().hash(state);
54        }
55    }
56}
57
58impl Literal {
59    /// Create a literal value expression
60    pub fn new(value: ScalarValue) -> Self {
61        Self::new_with_metadata(value, None)
62    }
63
64    /// Create a literal value expression
65    pub fn new_with_metadata(
66        value: ScalarValue,
67        metadata: Option<FieldMetadata>,
68    ) -> Self {
69        let mut field = Field::new("lit".to_string(), value.data_type(), value.is_null());
70
71        if let Some(metadata) = metadata {
72            field = metadata.add_to_field(field);
73        }
74
75        Self {
76            value,
77            field: field.into(),
78        }
79    }
80
81    /// Get the scalar value
82    pub fn value(&self) -> &ScalarValue {
83        &self.value
84    }
85}
86
87impl std::fmt::Display for Literal {
88    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
89        write!(f, "{}", self.value)
90    }
91}
92
93impl PhysicalExpr for Literal {
94    /// Return a reference to Any that can be used for downcasting
95    fn as_any(&self) -> &dyn Any {
96        self
97    }
98
99    fn data_type(&self, _input_schema: &Schema) -> Result<DataType> {
100        Ok(self.value.data_type())
101    }
102
103    fn nullable(&self, _input_schema: &Schema) -> Result<bool> {
104        Ok(self.value.is_null())
105    }
106
107    fn return_field(&self, _input_schema: &Schema) -> Result<FieldRef> {
108        Ok(Arc::clone(&self.field))
109    }
110
111    fn evaluate(&self, _batch: &RecordBatch) -> Result<ColumnarValue> {
112        Ok(ColumnarValue::Scalar(self.value.clone()))
113    }
114
115    fn children(&self) -> Vec<&Arc<dyn PhysicalExpr>> {
116        vec![]
117    }
118
119    fn with_new_children(
120        self: Arc<Self>,
121        _children: Vec<Arc<dyn PhysicalExpr>>,
122    ) -> Result<Arc<dyn PhysicalExpr>> {
123        Ok(self)
124    }
125
126    fn get_properties(&self, _children: &[ExprProperties]) -> Result<ExprProperties> {
127        Ok(ExprProperties {
128            sort_properties: SortProperties::Singleton,
129            range: Interval::try_new(self.value().clone(), self.value().clone())?,
130            preserves_lex_ordering: true,
131        })
132    }
133
134    fn fmt_sql(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
135        std::fmt::Display::fmt(self, f)
136    }
137}
138
139/// Create a literal expression
140pub fn lit<T: datafusion_expr::Literal>(value: T) -> Arc<dyn PhysicalExpr> {
141    match value.lit() {
142        Expr::Literal(v, _) => Arc::new(Literal::new(v)),
143        _ => unreachable!(),
144    }
145}
146
147#[cfg(test)]
148mod tests {
149    use super::*;
150
151    use arrow::array::Int32Array;
152    use arrow::datatypes::Field;
153    use datafusion_common::cast::as_int32_array;
154    use datafusion_physical_expr_common::physical_expr::fmt_sql;
155
156    #[test]
157    fn literal_i32() -> Result<()> {
158        // create an arbitrary record batch
159        let schema = Schema::new(vec![Field::new("a", DataType::Int32, true)]);
160        let a = Int32Array::from(vec![Some(1), None, Some(3), Some(4), Some(5)]);
161        let batch = RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)])?;
162
163        // create and evaluate a literal expression
164        let literal_expr = lit(42i32);
165        assert_eq!("42", format!("{literal_expr}"));
166
167        let literal_array = literal_expr
168            .evaluate(&batch)?
169            .into_array(batch.num_rows())
170            .expect("Failed to convert to array");
171        let literal_array = as_int32_array(&literal_array)?;
172
173        // note that the contents of the literal array are unrelated to the batch contents except for the length of the array
174        assert_eq!(literal_array.len(), 5); // 5 rows in the batch
175        for i in 0..literal_array.len() {
176            assert_eq!(literal_array.value(i), 42);
177        }
178
179        Ok(())
180    }
181
182    #[test]
183    fn test_fmt_sql() -> Result<()> {
184        // create and evaluate a literal expression
185        let expr = lit(42i32);
186        let display_string = expr.to_string();
187        assert_eq!(display_string, "42");
188        let sql_string = fmt_sql(expr.as_ref()).to_string();
189        assert_eq!(sql_string, "42");
190
191        Ok(())
192    }
193}
datafusion_physical_expr/expressions/literal.rs

datafusion_physical_expr/expressions/
literal.rs
