mz_timely_util/
columnar.rs

1// Copyright Materialize, Inc. and contributors. All rights reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License in the LICENSE file at the
6// root of this repository, or online at
7//
8//     http://www.apache.org/licenses/LICENSE-2.0
9//
10// Unless required by applicable law or agreed to in writing, software
11// distributed under the License is distributed on an "AS IS" BASIS,
12// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13// See the License for the specific language governing permissions and
14// limitations under the License.
15
16//! Container for columnar data.
17
18#![deny(missing_docs)]
19
20pub mod batcher;
21pub mod builder;
22pub mod consolidate;
23
24use std::hash::Hash;
25
26use columnar::Borrow;
27use columnar::bytes::indexed;
28use columnar::common::IterOwn;
29use columnar::{Columnar, Ref};
30use columnar::{FromBytes, Index, Len};
31use differential_dataflow::Hashable;
32use differential_dataflow::trace::implementations::merge_batcher::MergeBatcher;
33use timely::Accountable;
34use timely::bytes::arc::Bytes;
35use timely::container::{DrainContainer, PushInto};
36use timely::dataflow::channels::ContainerBytes;
37
38use crate::columnation::{ColInternalMerger, ColumnationStack};
39
40/// A batcher for columnar storage.
41pub type Col2ValBatcher<K, V, T, R> = MergeBatcher<
42    Column<((K, V), T, R)>,
43    batcher::Chunker<ColumnationStack<((K, V), T, R)>>,
44    ColInternalMerger<(K, V), T, R>,
45>;
46/// A batcher for columnar storage with unit values.
47pub type Col2KeyBatcher<K, T, R> = Col2ValBatcher<K, (), T, R>;
48
49/// A container based on a columnar store, encoded in aligned bytes.
50///
51/// The type can represent typed data, bytes from Timely, or an aligned allocation. The name
52/// is singular to express that the preferred format is [`Column::Align`]. The [`Column::Typed`]
53/// variant is used to construct the container, and it owns potentially multiple columns of data.
54pub enum Column<C: Columnar> {
55    /// The typed variant of the container.
56    Typed(C::Container),
57    /// The binary variant of the container.
58    Bytes(Bytes),
59    /// Relocated, aligned binary data, if `Bytes` doesn't work for some reason.
60    ///
61    /// Reasons could include misalignment, cloning of data, or wanting
62    /// to release the `Bytes` as a scarce resource.
63    ///
64    /// `Vec<u64>` guarantees `u64` alignment for the contained bytes.
65    Align(Vec<u64>),
66}
67
68impl<C: Columnar> Column<C> {
69    /// Borrows the container as a reference.
70    #[inline]
71    pub fn borrow(&self) -> <C::Container as Borrow>::Borrowed<'_> {
72        match self {
73            Column::Typed(t) => t.borrow(),
74            Column::Bytes(b) => <<C::Container as Borrow>::Borrowed<'_>>::from_bytes(
75                &mut indexed::decode(bytemuck::cast_slice(b)),
76            ),
77            Column::Align(a) => {
78                <<C::Container as Borrow>::Borrowed<'_>>::from_bytes(&mut indexed::decode(a))
79            }
80        }
81    }
82}
83
84impl<C: Columnar> Default for Column<C> {
85    fn default() -> Self {
86        Self::Typed(Default::default())
87    }
88}
89
90impl<C: Columnar> Clone for Column<C>
91where
92    C::Container: Clone,
93{
94    fn clone(&self) -> Self {
95        match self {
96            // Typed stays typed, although we would have the option to move to aligned data.
97            // If we did it might be confusing why we couldn't push into a cloned column.
98            Column::Typed(t) => Column::Typed(t.clone()),
99            Column::Bytes(b) => {
100                assert_eq!(b.len() % 8, 0);
101                Self::Align(bytemuck::allocation::pod_collect_to_vec(b))
102            }
103            Column::Align(a) => Column::Align(a.clone()),
104        }
105    }
106}
107
108impl<C: Columnar> Accountable for Column<C> {
109    #[inline]
110    fn record_count(&self) -> i64 {
111        self.borrow().len().try_into().expect("Must fit")
112    }
113}
114impl<C: Columnar> DrainContainer for Column<C> {
115    type Item<'a> = Ref<'a, C>;
116    type DrainIter<'a> = IterOwn<<C::Container as Borrow>::Borrowed<'a>>;
117    #[inline]
118    fn drain(&mut self) -> Self::DrainIter<'_> {
119        self.borrow().into_index_iter()
120    }
121}
122
123impl<C: Columnar, T> PushInto<T> for Column<C>
124where
125    C::Container: columnar::Push<T>,
126{
127    #[inline]
128    fn push_into(&mut self, item: T) {
129        use columnar::Push;
130        match self {
131            Column::Typed(t) => t.push(item),
132            Column::Align(_) | Column::Bytes(_) => {
133                // We really oughtn't be calling this in this case.
134                // We could convert to owned, but need more constraints on `C`.
135                unimplemented!("Pushing into Column::Bytes without first clearing");
136            }
137        }
138    }
139}
140
141impl<C: Columnar> ContainerBytes for Column<C> {
142    #[inline]
143    fn from_bytes(bytes: Bytes) -> Self {
144        // Our expectation / hope is that `bytes` is `u64` aligned and sized.
145        // If the alignment is borked, we can relocate. If the size is borked,
146        // not sure what we do in that case. An incorrect size indicates a problem
147        // of `into_bytes`, or a failure of the communication layer, both of which
148        // are unrecoverable.
149        assert_eq!(bytes.len() % 8, 0);
150        if let Ok(_) = bytemuck::try_cast_slice::<_, u64>(&bytes) {
151            Self::Bytes(bytes)
152        } else {
153            // We failed to cast the slice, so we'll reallocate. `Vec<u64>`
154            // is u64-aligned by construction.
155            Self::Align(bytemuck::allocation::pod_collect_to_vec(&bytes[..]))
156        }
157    }
158
159    #[inline]
160    fn length_in_bytes(&self) -> usize {
161        match self {
162            Column::Typed(t) => indexed::length_in_bytes(&t.borrow()),
163            Column::Bytes(b) => b.len(),
164            Column::Align(a) => 8 * a.len(),
165        }
166    }
167
168    #[inline]
169    fn into_bytes<W: ::std::io::Write>(&self, writer: &mut W) {
170        match self {
171            Column::Typed(t) => indexed::write(writer, &t.borrow()).unwrap(),
172            Column::Bytes(b) => writer.write_all(b).unwrap(),
173            Column::Align(a) => writer.write_all(bytemuck::cast_slice(a)).unwrap(),
174        }
175    }
176}
177
178/// An exchange function for columnar tuples of the form `((K, V), T, D)`. Rust has a hard
179/// time to figure out the lifetimes of the elements when specified as a closure, so we rather
180/// specify it as a function.
181#[inline(always)]
182pub fn columnar_exchange<K, V, T, D>(((k, _), _, _): &Ref<'_, ((K, V), T, D)>) -> u64
183where
184    K: Columnar,
185    for<'a> Ref<'a, K>: Hash,
186    V: Columnar,
187    D: Columnar,
188    T: Columnar,
189{
190    k.hashed()
191}
192
193#[cfg(test)]
194mod tests {
195    use timely::bytes::arc::BytesMut;
196    use timely::container::PushInto;
197    use timely::dataflow::channels::ContainerBytes;
198
199    use super::*;
200
201    /// Produce some bytes that are in columnar format.
202    fn raw_columnar_bytes() -> Vec<u8> {
203        let mut raw = Vec::new();
204        raw.extend(16_u64.to_le_bytes()); // offsets
205        raw.extend(28_u64.to_le_bytes()); // length
206        raw.extend(1_i32.to_le_bytes());
207        raw.extend(2_i32.to_le_bytes());
208        raw.extend(3_i32.to_le_bytes());
209        raw.extend([0, 0, 0, 0]); // padding
210        raw
211    }
212
213    #[mz_ore::test]
214    fn test_column_clone() {
215        let columns = Columnar::as_columns([1, 2, 3].iter());
216        let column_typed: Column<i32> = Column::Typed(columns);
217        let column_typed2 = column_typed.clone();
218
219        assert_eq!(
220            column_typed2.borrow().into_index_iter().collect::<Vec<_>>(),
221            vec![&1, &2, &3]
222        );
223
224        let bytes = BytesMut::from(raw_columnar_bytes()).freeze();
225        let column_bytes: Column<i32> = Column::Bytes(bytes);
226        let column_bytes2 = column_bytes.clone();
227
228        assert_eq!(
229            column_bytes2.borrow().into_index_iter().collect::<Vec<_>>(),
230            vec![&1, &2, &3]
231        );
232
233        let raw = raw_columnar_bytes();
234        let mut region: Vec<u64> = vec![0; raw.len() / 8];
235        let region_bytes = bytemuck::cast_slice_mut(&mut region[..]);
236        region_bytes[..raw.len()].copy_from_slice(&raw);
237        let column_align: Column<i32> = Column::Align(region);
238        let column_align2 = column_align.clone();
239
240        assert_eq!(
241            column_align2.borrow().into_index_iter().collect::<Vec<_>>(),
242            vec![&1, &2, &3]
243        );
244    }
245
246    /// Assert the desired contents of raw_columnar_bytes so that diagnosing test failures is
247    /// easier.
248    #[mz_ore::test]
249    fn test_column_known_bytes() {
250        let mut column: Column<i32> = Default::default();
251        column.push_into(1);
252        column.push_into(2);
253        column.push_into(3);
254        let mut data = Vec::new();
255        column.into_bytes(&mut std::io::Cursor::new(&mut data));
256        assert_eq!(data, raw_columnar_bytes());
257    }
258
259    #[mz_ore::test]
260    fn test_column_from_bytes() {
261        let raw = raw_columnar_bytes();
262
263        let buf = vec![0; raw.len() + 8];
264        let align = buf.as_ptr().align_offset(std::mem::size_of::<u64>());
265        let mut bytes_mut = BytesMut::from(buf);
266        let _ = bytes_mut.extract_to(align);
267        bytes_mut[..raw.len()].copy_from_slice(&raw);
268        let aligned_bytes = bytes_mut.extract_to(raw.len());
269
270        let column: Column<i32> = Column::from_bytes(aligned_bytes);
271        assert!(matches!(column, Column::Bytes(_)));
272        assert_eq!(
273            column.borrow().into_index_iter().collect::<Vec<_>>(),
274            vec![&1, &2, &3]
275        );
276
277        let buf = vec![0; raw.len() + 8];
278        let align = buf.as_ptr().align_offset(std::mem::size_of::<u64>());
279        let mut bytes_mut = BytesMut::from(buf);
280        let _ = bytes_mut.extract_to(align + 1);
281        bytes_mut[..raw.len()].copy_from_slice(&raw);
282        let unaligned_bytes = bytes_mut.extract_to(raw.len());
283
284        let column: Column<i32> = Column::from_bytes(unaligned_bytes);
285        assert!(matches!(column, Column::Align(_)));
286        assert_eq!(
287            column.borrow().into_index_iter().collect::<Vec<_>>(),
288            vec![&1, &2, &3]
289        );
290    }
291}
mz_timely_util/columnar.rs

mz_timely_util/
columnar.rs
