arrow_buffer/buffer/
null.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 crate::bit_iterator::{BitIndexIterator, BitIterator, BitSliceIterator};
19use crate::buffer::BooleanBuffer;
20use crate::{Buffer, MutableBuffer};
21
22/// A [`BooleanBuffer`] used to encode validity (null values) for Arrow arrays
23///
24/// In the [Arrow specification], array validity is encoded in a packed bitmask with a
25/// `true` value indicating the corresponding slot is not null, and `false` indicating
26/// that it is null.
27///
28/// # See also
29/// * [`NullBufferBuilder`] for creating `NullBuffer`s
30///
31/// [Arrow specification]: https://arrow.apache.org/docs/format/Columnar.html#validity-bitmaps
32/// [`NullBufferBuilder`]: crate::NullBufferBuilder
33#[derive(Debug, Clone, Eq, PartialEq)]
34pub struct NullBuffer {
35    buffer: BooleanBuffer,
36    null_count: usize,
37}
38
39impl NullBuffer {
40    /// Create a new [`NullBuffer`] computing the null count
41    pub fn new(buffer: BooleanBuffer) -> Self {
42        let null_count = buffer.len() - buffer.count_set_bits();
43        Self { buffer, null_count }
44    }
45
46    /// Create a new [`NullBuffer`] of length `len` where all values are null
47    pub fn new_null(len: usize) -> Self {
48        Self {
49            buffer: BooleanBuffer::new_unset(len),
50            null_count: len,
51        }
52    }
53
54    /// Create a new [`NullBuffer`] of length `len` where all values are valid
55    ///
56    /// Note: it is more efficient to not set the null buffer if it is known to
57    /// be all valid (aka all values are not null)
58    pub fn new_valid(len: usize) -> Self {
59        Self {
60            buffer: BooleanBuffer::new_set(len),
61            null_count: 0,
62        }
63    }
64
65    /// Create a new [`NullBuffer`] with the provided `buffer` and `null_count`
66    ///
67    /// # Safety
68    ///
69    /// `buffer` must contain `null_count` `0` bits
70    pub unsafe fn new_unchecked(buffer: BooleanBuffer, null_count: usize) -> Self {
71        Self { buffer, null_count }
72    }
73
74    /// Computes the union of the nulls in two optional [`NullBuffer`]
75    ///
76    /// This is commonly used by binary operations where the result is NULL if either
77    /// of the input values is NULL. Handling the null mask separately in this way
78    /// can yield significant performance improvements over an iterator approach
79    pub fn union(lhs: Option<&NullBuffer>, rhs: Option<&NullBuffer>) -> Option<NullBuffer> {
80        match (lhs, rhs) {
81            (Some(lhs), Some(rhs)) if lhs.null_count() > 0 || rhs.null_count() > 0 => {
82                Some(Self::new(lhs.inner() & rhs.inner()))
83            }
84            (Some(n), None) | (None, Some(n)) if n.null_count() > 0 => Some(n.clone()),
85            (_, _) => None,
86        }
87    }
88
89    /// Computes the union of the nulls in multiple optional [`NullBuffer`]s
90    ///
91    /// See [`union`](Self::union)
92    pub fn union_many<'a>(
93        nulls: impl IntoIterator<Item = Option<&'a NullBuffer>>,
94    ) -> Option<NullBuffer> {
95        // Unwrap to BooleanBuffer because BitAndAssign is not implemented for NullBuffer
96        let mut buffers = nulls.into_iter().filter_map(|nb| match nb {
97            Some(nb) if nb.null_count > 0 => Some(nb.inner()),
98            _ => None,
99        });
100        let first = buffers.next()?;
101        let mut result = first.clone();
102        for buf in buffers {
103            result &= buf;
104        }
105        Some(Self::new(result))
106    }
107
108    /// Returns true if all nulls in `other` also exist in self
109    pub fn contains(&self, other: &NullBuffer) -> bool {
110        if other.null_count == 0 {
111            return true;
112        }
113        let lhs = self.inner().bit_chunks().iter_padded();
114        let rhs = other.inner().bit_chunks().iter_padded();
115        lhs.zip(rhs).all(|(l, r)| (l & !r) == 0)
116    }
117
118    /// Returns a new [`NullBuffer`] where each bit in the current null buffer
119    /// is repeated `count` times. This is useful for masking the nulls of
120    /// the child of a FixedSizeListArray based on its parent
121    pub fn expand(&self, count: usize) -> Self {
122        let capacity = self.buffer.len().checked_mul(count).unwrap();
123        let mut buffer = MutableBuffer::new_null(capacity);
124
125        // Expand each bit within `null_mask` into `element_len`
126        // bits, constructing the implicit mask of the child elements
127        for i in 0..self.buffer.len() {
128            if self.is_null(i) {
129                continue;
130            }
131            for j in 0..count {
132                crate::bit_util::set_bit(buffer.as_mut(), i * count + j)
133            }
134        }
135        Self {
136            buffer: BooleanBuffer::new(buffer.into(), 0, capacity),
137            null_count: self.null_count * count,
138        }
139    }
140
141    /// Returns the length of this [`NullBuffer`] in bits
142    #[inline]
143    pub fn len(&self) -> usize {
144        self.buffer.len()
145    }
146
147    /// Returns the offset of this [`NullBuffer`] in bits
148    #[inline]
149    pub fn offset(&self) -> usize {
150        self.buffer.offset()
151    }
152
153    /// Returns true if this [`NullBuffer`] is empty
154    #[inline]
155    pub fn is_empty(&self) -> bool {
156        self.buffer.is_empty()
157    }
158
159    /// Free up unused memory.
160    pub fn shrink_to_fit(&mut self) {
161        self.buffer.shrink_to_fit();
162    }
163
164    /// Returns the null count for this [`NullBuffer`]
165    #[inline]
166    pub fn null_count(&self) -> usize {
167        self.null_count
168    }
169
170    /// Returns `true` if the value at `idx` is not null
171    #[inline]
172    pub fn is_valid(&self, idx: usize) -> bool {
173        self.buffer.value(idx)
174    }
175
176    /// Returns `true` if the value at `idx` is null
177    #[inline]
178    pub fn is_null(&self, idx: usize) -> bool {
179        !self.is_valid(idx)
180    }
181
182    /// Returns the packed validity of this [`NullBuffer`] not including any offset
183    #[inline]
184    pub fn validity(&self) -> &[u8] {
185        self.buffer.values()
186    }
187
188    /// Slices this [`NullBuffer`] by the provided `offset` and `length`
189    pub fn slice(&self, offset: usize, len: usize) -> Self {
190        Self::new(self.buffer.slice(offset, len))
191    }
192
193    /// Returns an iterator over the bits in this [`NullBuffer`]
194    ///
195    /// * `true` indicates that the corresponding value is not NULL
196    /// * `false` indicates that the corresponding value is NULL
197    ///
198    /// Note: [`Self::valid_indices`] will be significantly faster for most use-cases
199    pub fn iter(&self) -> BitIterator<'_> {
200        self.buffer.iter()
201    }
202
203    /// Returns a [`BitIndexIterator`] over the valid indices in this [`NullBuffer`]
204    ///
205    /// Valid indices indicate the corresponding value is not NULL
206    pub fn valid_indices(&self) -> BitIndexIterator<'_> {
207        self.buffer.set_indices()
208    }
209
210    /// Returns a [`BitSliceIterator`] yielding contiguous ranges of valid indices
211    ///
212    /// Valid indices indicate the corresponding value is not NULL
213    pub fn valid_slices(&self) -> BitSliceIterator<'_> {
214        self.buffer.set_slices()
215    }
216
217    /// Calls the provided closure for each index in this null mask that is set
218    #[inline]
219    pub fn try_for_each_valid_idx<E, F: FnMut(usize) -> Result<(), E>>(
220        &self,
221        f: F,
222    ) -> Result<(), E> {
223        if self.null_count == self.len() {
224            return Ok(());
225        }
226        self.valid_indices().try_for_each(f)
227    }
228
229    /// Returns the inner [`BooleanBuffer`]
230    #[inline]
231    pub fn inner(&self) -> &BooleanBuffer {
232        &self.buffer
233    }
234
235    /// Returns the inner [`BooleanBuffer`]
236    #[inline]
237    pub fn into_inner(self) -> BooleanBuffer {
238        self.buffer
239    }
240
241    /// Returns the underlying [`Buffer`]
242    #[inline]
243    pub fn buffer(&self) -> &Buffer {
244        self.buffer.inner()
245    }
246
247    /// Create a [`NullBuffer`] from an *unsliced* validity bitmap (`offset = 0` **bits**) of length `len`.
248    ///
249    /// Returns `None` if there are no nulls (all values valid).
250    pub fn from_unsliced_buffer(buffer: impl Into<Buffer>, len: usize) -> Option<Self> {
251        let bb = BooleanBuffer::new(buffer.into(), 0, len);
252        let nb = NullBuffer::new(bb);
253        (nb.null_count() > 0).then_some(nb)
254    }
255
256    /// Claim memory used by this null buffer in the provided memory pool.
257    #[cfg(feature = "pool")]
258    pub fn claim(&self, pool: &dyn crate::MemoryPool) {
259        // NullBuffer wraps a BooleanBuffer which wraps a Buffer
260        self.buffer.inner().claim(pool);
261    }
262}
263
264impl<'a> IntoIterator for &'a NullBuffer {
265    type Item = bool;
266    type IntoIter = BitIterator<'a>;
267
268    fn into_iter(self) -> Self::IntoIter {
269        self.buffer.iter()
270    }
271}
272
273impl From<BooleanBuffer> for NullBuffer {
274    fn from(value: BooleanBuffer) -> Self {
275        Self::new(value)
276    }
277}
278
279impl From<&[bool]> for NullBuffer {
280    fn from(value: &[bool]) -> Self {
281        BooleanBuffer::from(value).into()
282    }
283}
284
285impl<const N: usize> From<&[bool; N]> for NullBuffer {
286    fn from(value: &[bool; N]) -> Self {
287        value[..].into()
288    }
289}
290
291impl From<Vec<bool>> for NullBuffer {
292    fn from(value: Vec<bool>) -> Self {
293        BooleanBuffer::from(value).into()
294    }
295}
296
297impl FromIterator<bool> for NullBuffer {
298    fn from_iter<T: IntoIterator<Item = bool>>(iter: T) -> Self {
299        BooleanBuffer::from_iter(iter).into()
300    }
301}
302
303#[cfg(test)]
304mod tests {
305    use super::*;
306
307    #[test]
308    fn test_size() {
309        // This tests that the niche optimisation eliminates the overhead of an option
310        assert_eq!(
311            std::mem::size_of::<NullBuffer>(),
312            std::mem::size_of::<Option<NullBuffer>>()
313        );
314    }
315
316    #[test]
317    fn test_from_unsliced_buffer_with_nulls() {
318        // 0b10110010 → null(0), valid(1), null(2), null(3), valid(4), valid(5), null(6), valid(7)
319        let buf = Buffer::from([0b10110010u8]);
320        let result = NullBuffer::from_unsliced_buffer(buf, 8);
321        assert!(result.is_some());
322        let nb = result.unwrap();
323        assert_eq!(nb.len(), 8);
324        assert_eq!(nb.null_count(), 4);
325        assert!(nb.is_null(0));
326        assert!(nb.is_valid(1));
327        assert!(nb.is_null(2));
328        assert!(nb.is_null(3));
329        assert!(nb.is_valid(4));
330        assert!(nb.is_valid(5));
331        assert!(nb.is_null(6));
332        assert!(nb.is_valid(7));
333    }
334
335    #[test]
336    fn test_from_unsliced_buffer_all_valid() {
337        // All bits set = all valid, no nulls
338        let buf = Buffer::from([0b11111111u8]);
339        let result = NullBuffer::from_unsliced_buffer(buf, 8);
340        assert!(result.is_none());
341    }
342
343    #[test]
344    fn test_from_unsliced_buffer_all_null() {
345        // No bits set = all null
346        let buf = Buffer::from([0b00000000u8]);
347        let result = NullBuffer::from_unsliced_buffer(buf, 8);
348        assert!(result.is_some());
349        let nb = result.unwrap();
350        assert_eq!(nb.len(), 8);
351        assert_eq!(nb.null_count(), 8);
352    }
353
354    #[test]
355    fn test_from_unsliced_buffer_empty() {
356        let buf = Buffer::from([]);
357        let result = NullBuffer::from_unsliced_buffer(buf, 0);
358        assert!(result.is_none());
359    }
360
361    #[test]
362    fn test_union_many_all_none() {
363        let result = NullBuffer::union_many([None, None, None]);
364        assert!(result.is_none());
365    }
366
367    #[test]
368    fn test_union_many_single_some() {
369        let a = NullBuffer::from(&[true, false, true, true]);
370        let result = NullBuffer::union_many([Some(&a)]);
371        assert_eq!(result, Some(a));
372    }
373
374    #[test]
375    fn test_union_many_two_inputs() {
376        let a = NullBuffer::from(&[true, false, true, true]);
377        let b = NullBuffer::from(&[true, true, false, true]);
378        let result = NullBuffer::union_many([Some(&a), Some(&b)]);
379        let expected = NullBuffer::union(Some(&a), Some(&b));
380        assert_eq!(result, expected);
381    }
382
383    #[test]
384    fn test_union_many_three_inputs() {
385        let a = NullBuffer::from(&[true, false, true, true]);
386        let b = NullBuffer::from(&[true, true, false, true]);
387        let c = NullBuffer::from(&[false, true, true, true]);
388        let result = NullBuffer::union_many([Some(&a), Some(&b), Some(&c)]);
389        let expected = NullBuffer::from(&[false, false, false, true]);
390        assert_eq!(result, Some(expected));
391    }
392
393    #[test]
394    fn test_union_many_mixed_none() {
395        let a = NullBuffer::from(&[true, false, true, true]);
396        let b = NullBuffer::from(&[false, true, true, true]);
397        let result = NullBuffer::union_many([Some(&a), None, Some(&b)]);
398        let expected = NullBuffer::union(Some(&a), Some(&b));
399        assert_eq!(result, expected);
400    }
401
402    #[test]
403    fn test_union_many_empty_slice() {
404        let result = NullBuffer::union_many([] as [Option<&NullBuffer>; 0]);
405        assert!(result.is_none());
406    }
407
408    #[test]
409    fn test_union_many_no_nulls() {
410        let a = NullBuffer::from(&[true, true, true, true]);
411
412        let result = NullBuffer::union_many([Some(&a), Some(&a), Some(&a)]);
413        assert_eq!(result, None);
414    }
415
416    #[test]
417    fn test_union_no_nulls() {
418        let a = NullBuffer::from(&[true, true, true, true]);
419
420        let result = NullBuffer::union(Some(&a), Some(&a));
421        assert_eq!(result, None);
422
423        let result = NullBuffer::union(Some(&a), None);
424        assert_eq!(result, None);
425
426        let result = NullBuffer::union(None, Some(&a));
427        assert_eq!(result, None);
428    }
429
430    #[test]
431    fn test_union_nulls_one_side() {
432        let all_valid = NullBuffer::from(&[true, true, true, true]);
433        let all_null = NullBuffer::from(&[false, false, false, false]);
434
435        let result = NullBuffer::union(Some(&all_valid), Some(&all_null));
436        assert_eq!(result, Some(all_null.clone()));
437
438        let result = NullBuffer::union(Some(&all_null), Some(&all_valid));
439        assert_eq!(result, Some(all_null.clone()));
440    }
441}
arrow_buffer/buffer/null.rs

arrow_buffer/buffer/
null.rs
