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 super::private::Sealed for NullArray {}
80
81impl Array for NullArray {
82    fn as_any(&self) -> &dyn Any {
83        self
84    }
85
86    fn to_data(&self) -> ArrayData {
87        self.clone().into()
88    }
89
90    fn into_data(self) -> ArrayData {
91        self.into()
92    }
93
94    fn data_type(&self) -> &DataType {
95        &DataType::Null
96    }
97
98    fn slice(&self, offset: usize, length: usize) -> ArrayRef {
99        Arc::new(self.slice(offset, length))
100    }
101
102    fn len(&self) -> usize {
103        self.len
104    }
105
106    fn is_empty(&self) -> bool {
107        self.len == 0
108    }
109
110    fn offset(&self) -> usize {
111        0
112    }
113
114    fn nulls(&self) -> Option<&NullBuffer> {
115        None
116    }
117
118    fn logical_nulls(&self) -> Option<NullBuffer> {
119        (self.len != 0).then(|| NullBuffer::new_null(self.len))
120    }
121
122    fn is_nullable(&self) -> bool {
123        !self.is_empty()
124    }
125
126    fn logical_null_count(&self) -> usize {
127        self.len
128    }
129
130    fn get_buffer_memory_size(&self) -> usize {
131        0
132    }
133
134    fn get_array_memory_size(&self) -> usize {
135        std::mem::size_of::<Self>()
136    }
137}
138
139impl From<ArrayData> for NullArray {
140    fn from(data: ArrayData) -> Self {
141        assert_eq!(
142            data.data_type(),
143            &DataType::Null,
144            "NullArray data type should be Null"
145        );
146        assert_eq!(
147            data.buffers().len(),
148            0,
149            "NullArray data should contain 0 buffers"
150        );
151        assert!(
152            data.nulls().is_none(),
153            "NullArray data should not contain a null buffer, as no buffers are required"
154        );
155        Self { len: data.len() }
156    }
157}
158
159impl From<NullArray> for ArrayData {
160    fn from(array: NullArray) -> Self {
161        let builder = ArrayDataBuilder::new(DataType::Null).len(array.len);
162        unsafe { builder.build_unchecked() }
163    }
164}
165
166impl std::fmt::Debug for NullArray {
167    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
168        write!(f, "NullArray({})", self.len())
169    }
170}
171
172#[cfg(test)]
173mod tests {
174    use super::*;
175    use crate::{Int64Array, StructArray, make_array};
176    use arrow_data::transform::MutableArrayData;
177    use arrow_schema::Field;
178
179    #[test]
180    fn test_null_array() {
181        let null_arr = NullArray::new(32);
182
183        assert_eq!(null_arr.len(), 32);
184        assert_eq!(null_arr.null_count(), 0);
185        assert_eq!(null_arr.logical_null_count(), 32);
186        assert_eq!(null_arr.logical_nulls().unwrap().null_count(), 32);
187        assert!(null_arr.is_valid(0));
188        assert!(null_arr.is_nullable());
189    }
190
191    #[test]
192    fn test_null_array_slice() {
193        let array1 = NullArray::new(32);
194
195        let array2 = array1.slice(8, 16);
196        assert_eq!(array2.len(), 16);
197        assert_eq!(array2.null_count(), 0);
198        assert_eq!(array2.logical_null_count(), 16);
199        assert_eq!(array2.logical_nulls().unwrap().null_count(), 16);
200        assert!(array2.is_valid(0));
201        assert!(array2.is_nullable());
202    }
203
204    #[test]
205    fn test_debug_null_array() {
206        let array = NullArray::new(1024 * 1024);
207        assert_eq!(format!("{array:?}"), "NullArray(1048576)");
208    }
209
210    #[test]
211    fn test_null_array_with_parent_null_buffer() {
212        let null_array = NullArray::new(1);
213        let int_array = Int64Array::from(vec![42]);
214
215        let fields = vec![
216            Field::new("a", DataType::Int64, true),
217            Field::new("b", DataType::Null, true),
218        ];
219
220        let struct_array_data = ArrayData::builder(DataType::Struct(fields.into()))
221            .len(1)
222            .add_child_data(int_array.to_data())
223            .add_child_data(null_array.to_data())
224            .build()
225            .unwrap();
226
227        let mut mutable = MutableArrayData::new(vec![&struct_array_data], true, 1);
228
229        // Simulate a NULL value in the parent array, for instance, if array being queried by
230        // invalid index
231        mutable.extend_nulls(1);
232        let data = mutable.freeze();
233
234        let struct_array = Arc::new(StructArray::from(data.clone()));
235        assert!(make_array(data) == struct_array);
236    }
237}
arrow_array/array/null_array.rs

arrow_array/array/
null_array.rs
