arrow_array/array/
null_array.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
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8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
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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//! Contains the `NullArray` type.
19
20use crate::builder::NullBuilder;
21use crate::{Array, ArrayRef};
22use arrow_buffer::buffer::NullBuffer;
23use arrow_data::{ArrayData, ArrayDataBuilder};
24use arrow_schema::DataType;
25use std::any::Any;
26use std::sync::Arc;
27
28/// An array of [null values](https://arrow.apache.org/docs/format/Columnar.html#null-layout)
29///
30/// A `NullArray` is a simplified array where all values are null.
31///
32/// # Example: Create an array
33///
34/// ```
35/// use arrow_array::{Array, NullArray};
36///
37/// let array = NullArray::new(10);
38///
39/// assert!(array.is_nullable());
40/// assert_eq!(array.len(), 10);
41/// assert_eq!(array.null_count(), 0);
42/// assert_eq!(array.logical_null_count(), 10);
43/// assert_eq!(array.logical_nulls().unwrap().null_count(), 10);
44/// ```
45#[derive(Clone)]
46pub struct NullArray {
47    len: usize,
48}
49
50impl NullArray {
51    /// Create a new [`NullArray`] of the specified length
52    ///
53    /// *Note*: Use [`crate::array::new_null_array`] if you need an array of some
54    /// other [`DataType`].
55    ///
56    pub fn new(length: usize) -> Self {
57        Self { len: length }
58    }
59
60    /// Returns a zero-copy slice of this array with the indicated offset and length.
61    pub fn slice(&self, offset: usize, len: usize) -> Self {
62        assert!(
63            offset.saturating_add(len) <= self.len,
64            "the length + offset of the sliced BooleanBuffer cannot exceed the existing length"
65        );
66
67        Self { len }
68    }
69
70    /// Returns a new null array builder
71    ///
72    /// Note that the `capacity` parameter to this function is _deprecated_. It
73    /// now does nothing, and will be removed in a future version.
74    pub fn builder(_capacity: usize) -> NullBuilder {
75        NullBuilder::new()
76    }
77}
78
79impl Array for NullArray {
80    fn as_any(&self) -> &dyn Any {
81        self
82    }
83
84    fn to_data(&self) -> ArrayData {
85        self.clone().into()
86    }
87
88    fn into_data(self) -> ArrayData {
89        self.into()
90    }
91
92    fn data_type(&self) -> &DataType {
93        &DataType::Null
94    }
95
96    fn slice(&self, offset: usize, length: usize) -> ArrayRef {
97        Arc::new(self.slice(offset, length))
98    }
99
100    fn len(&self) -> usize {
101        self.len
102    }
103
104    fn is_empty(&self) -> bool {
105        self.len == 0
106    }
107
108    fn offset(&self) -> usize {
109        0
110    }
111
112    fn nulls(&self) -> Option<&NullBuffer> {
113        None
114    }
115
116    fn logical_nulls(&self) -> Option<NullBuffer> {
117        (self.len != 0).then(|| NullBuffer::new_null(self.len))
118    }
119
120    fn is_nullable(&self) -> bool {
121        !self.is_empty()
122    }
123
124    fn logical_null_count(&self) -> usize {
125        self.len
126    }
127
128    fn get_buffer_memory_size(&self) -> usize {
129        0
130    }
131
132    fn get_array_memory_size(&self) -> usize {
133        std::mem::size_of::<Self>()
134    }
135}
136
137impl From<ArrayData> for NullArray {
138    fn from(data: ArrayData) -> Self {
139        assert_eq!(
140            data.data_type(),
141            &DataType::Null,
142            "NullArray data type should be Null"
143        );
144        assert_eq!(
145            data.buffers().len(),
146            0,
147            "NullArray data should contain 0 buffers"
148        );
149        assert!(
150            data.nulls().is_none(),
151            "NullArray data should not contain a null buffer, as no buffers are required"
152        );
153        Self { len: data.len() }
154    }
155}
156
157impl From<NullArray> for ArrayData {
158    fn from(array: NullArray) -> Self {
159        let builder = ArrayDataBuilder::new(DataType::Null).len(array.len);
160        unsafe { builder.build_unchecked() }
161    }
162}
163
164impl std::fmt::Debug for NullArray {
165    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
166        write!(f, "NullArray({})", self.len())
167    }
168}
169
170#[cfg(test)]
171mod tests {
172    use super::*;
173    use crate::{make_array, Int64Array, StructArray};
174    use arrow_data::transform::MutableArrayData;
175    use arrow_schema::Field;
176
177    #[test]
178    fn test_null_array() {
179        let null_arr = NullArray::new(32);
180
181        assert_eq!(null_arr.len(), 32);
182        assert_eq!(null_arr.null_count(), 0);
183        assert_eq!(null_arr.logical_null_count(), 32);
184        assert_eq!(null_arr.logical_nulls().unwrap().null_count(), 32);
185        assert!(null_arr.is_valid(0));
186        assert!(null_arr.is_nullable());
187    }
188
189    #[test]
190    fn test_null_array_slice() {
191        let array1 = NullArray::new(32);
192
193        let array2 = array1.slice(8, 16);
194        assert_eq!(array2.len(), 16);
195        assert_eq!(array2.null_count(), 0);
196        assert_eq!(array2.logical_null_count(), 16);
197        assert_eq!(array2.logical_nulls().unwrap().null_count(), 16);
198        assert!(array2.is_valid(0));
199        assert!(array2.is_nullable());
200    }
201
202    #[test]
203    fn test_debug_null_array() {
204        let array = NullArray::new(1024 * 1024);
205        assert_eq!(format!("{array:?}"), "NullArray(1048576)");
206    }
207
208    #[test]
209    fn test_null_array_with_parent_null_buffer() {
210        let null_array = NullArray::new(1);
211        let int_array = Int64Array::from(vec![42]);
212
213        let fields = vec![
214            Field::new("a", DataType::Int64, true),
215            Field::new("b", DataType::Null, true),
216        ];
217
218        let struct_array_data = ArrayData::builder(DataType::Struct(fields.into()))
219            .len(1)
220            .add_child_data(int_array.to_data())
221            .add_child_data(null_array.to_data())
222            .build()
223            .unwrap();
224
225        let mut mutable = MutableArrayData::new(vec![&struct_array_data], true, 1);
226
227        // Simulate a NULL value in the parent array, for instance, if array being queried by
228        // invalid index
229        mutable.extend_nulls(1);
230        let data = mutable.freeze();
231
232        let struct_array = Arc::new(StructArray::from(data.clone()));
233        assert!(make_array(data) == struct_array);
234    }
235}
arrow_array/array/null_array.rs

arrow_array/array/
null_array.rs
