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, SizableContainer};
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
141/// Words per 2 MiB. `length_in_words` returns serialized size in `u64` units,
142/// so this is the page count we round up to. Picked to match
143/// [`builder::ColumnBuilder`]'s output granularity so chunks shipped from the
144/// merger and chunks shipped from the builder are sized comparably.
145const SHIP_WORDS: usize = 1 << 18;
146
147/// Returns true once the serialized size of `borrow` is within 10% of the next
148/// `SHIP_WORDS` boundary.
149///
150/// Same heuristic as `ColumnBuilder::push_into`; lifted out so the merger and
151/// the `SizableContainer` impl agree on the ship signal.
152#[inline]
153pub(crate) fn at_serialized_capacity<'a, A>(borrow: &A) -> bool
154where
155    A: columnar::AsBytes<'a>,
156{
157    let words = indexed::length_in_words(borrow);
158    let round = (words + (SHIP_WORDS - 1)) & !(SHIP_WORDS - 1);
159    round - words < round / 10
160}
161
162impl<C: Columnar> SizableContainer for Column<C> {
163    fn at_capacity(&self) -> bool {
164        // Match `ColumnBuilder`'s ship heuristic: serialized size within 10%
165        // of the next 2 MiB. Aligns chunk-size choices across the two paths
166        // and keeps recipients dealing with a single granularity.
167        //
168        // Serialized chunks (`Bytes` / `Align`) have no typed builder to push
169        // into, so they're trivially "at capacity" — there's no further work
170        // they can absorb.
171        match self {
172            Column::Typed(c) => at_serialized_capacity(&c.borrow()),
173            Column::Bytes(_) | Column::Align(_) => true,
174        }
175    }
176
177    fn ensure_capacity(&mut self, _stash: &mut Option<Self>) {
178        // No pre-reservation: chunks are recycled by the merge framework, so
179        // leaf capacities settle to steady-state after the first round and
180        // there is nothing useful to reserve up front. The `SizableContainer`
181        // impl exists so `at_capacity` is callable on result chunks during
182        // `Merger::merge` orchestration; `ensure_capacity` is a required
183        // method on the trait but has no work to do here.
184    }
185}
186
187impl<C: Columnar> ContainerBytes for Column<C> {
188    #[inline]
189    fn from_bytes(bytes: Bytes) -> Self {
190        // Our expectation / hope is that `bytes` is `u64` aligned and sized.
191        // If the alignment is borked, we can relocate. If the size is borked,
192        // not sure what we do in that case. An incorrect size indicates a problem
193        // of `into_bytes`, or a failure of the communication layer, both of which
194        // are unrecoverable.
195        assert_eq!(bytes.len() % 8, 0);
196        if let Ok(_) = bytemuck::try_cast_slice::<_, u64>(&bytes) {
197            Self::Bytes(bytes)
198        } else {
199            // We failed to cast the slice, so we'll reallocate. `Vec<u64>`
200            // is u64-aligned by construction.
201            Self::Align(bytemuck::allocation::pod_collect_to_vec(&bytes[..]))
202        }
203    }
204
205    #[inline]
206    fn length_in_bytes(&self) -> usize {
207        match self {
208            Column::Typed(t) => indexed::length_in_bytes(&t.borrow()),
209            Column::Bytes(b) => b.len(),
210            Column::Align(a) => 8 * a.len(),
211        }
212    }
213
214    #[inline]
215    fn into_bytes<W: ::std::io::Write>(&self, writer: &mut W) {
216        match self {
217            Column::Typed(t) => indexed::write(writer, &t.borrow()).unwrap(),
218            Column::Bytes(b) => writer.write_all(b).unwrap(),
219            Column::Align(a) => writer.write_all(bytemuck::cast_slice(a)).unwrap(),
220        }
221    }
222}
223
224/// An exchange function for columnar tuples of the form `((K, V), T, D)`. Rust has a hard
225/// time to figure out the lifetimes of the elements when specified as a closure, so we rather
226/// specify it as a function.
227#[inline(always)]
228pub fn columnar_exchange<K, V, T, D>(((k, _), _, _): &Ref<'_, ((K, V), T, D)>) -> u64
229where
230    K: Columnar,
231    for<'a> Ref<'a, K>: Hash,
232    V: Columnar,
233    D: Columnar,
234    T: Columnar,
235{
236    k.hashed()
237}
238
239#[cfg(test)]
240mod tests {
241    use timely::bytes::arc::BytesMut;
242    use timely::container::PushInto;
243    use timely::dataflow::channels::ContainerBytes;
244
245    use super::*;
246
247    /// Produce some bytes that are in columnar format.
248    fn raw_columnar_bytes() -> Vec<u8> {
249        let mut raw = Vec::new();
250        raw.extend(16_u64.to_le_bytes()); // offsets
251        raw.extend(28_u64.to_le_bytes()); // length
252        raw.extend(1_i32.to_le_bytes());
253        raw.extend(2_i32.to_le_bytes());
254        raw.extend(3_i32.to_le_bytes());
255        raw.extend([0, 0, 0, 0]); // padding
256        raw
257    }
258
259    #[mz_ore::test]
260    fn test_column_clone() {
261        let columns = Columnar::as_columns([1, 2, 3].iter());
262        let column_typed: Column<i32> = Column::Typed(columns);
263        let column_typed2 = column_typed.clone();
264
265        assert_eq!(
266            column_typed2.borrow().into_index_iter().collect::<Vec<_>>(),
267            vec![&1, &2, &3]
268        );
269
270        let bytes = BytesMut::from(raw_columnar_bytes()).freeze();
271        let column_bytes: Column<i32> = Column::Bytes(bytes);
272        let column_bytes2 = column_bytes.clone();
273
274        assert_eq!(
275            column_bytes2.borrow().into_index_iter().collect::<Vec<_>>(),
276            vec![&1, &2, &3]
277        );
278
279        let raw = raw_columnar_bytes();
280        let mut region: Vec<u64> = vec![0; raw.len() / 8];
281        let region_bytes = bytemuck::cast_slice_mut(&mut region[..]);
282        region_bytes[..raw.len()].copy_from_slice(&raw);
283        let column_align: Column<i32> = Column::Align(region);
284        let column_align2 = column_align.clone();
285
286        assert_eq!(
287            column_align2.borrow().into_index_iter().collect::<Vec<_>>(),
288            vec![&1, &2, &3]
289        );
290    }
291
292    /// Assert the desired contents of raw_columnar_bytes so that diagnosing test failures is
293    /// easier.
294    #[mz_ore::test]
295    fn test_column_known_bytes() {
296        let mut column: Column<i32> = Default::default();
297        column.push_into(1);
298        column.push_into(2);
299        column.push_into(3);
300        let mut data = Vec::new();
301        column.into_bytes(&mut std::io::Cursor::new(&mut data));
302        assert_eq!(data, raw_columnar_bytes());
303    }
304
305    #[mz_ore::test]
306    fn test_column_from_bytes() {
307        let raw = raw_columnar_bytes();
308
309        let buf = vec![0; raw.len() + 8];
310        let align = buf.as_ptr().align_offset(std::mem::size_of::<u64>());
311        let mut bytes_mut = BytesMut::from(buf);
312        let _ = bytes_mut.extract_to(align);
313        bytes_mut[..raw.len()].copy_from_slice(&raw);
314        let aligned_bytes = bytes_mut.extract_to(raw.len());
315
316        let column: Column<i32> = Column::from_bytes(aligned_bytes);
317        assert!(matches!(column, Column::Bytes(_)));
318        assert_eq!(
319            column.borrow().into_index_iter().collect::<Vec<_>>(),
320            vec![&1, &2, &3]
321        );
322
323        let buf = vec![0; raw.len() + 8];
324        let align = buf.as_ptr().align_offset(std::mem::size_of::<u64>());
325        let mut bytes_mut = BytesMut::from(buf);
326        let _ = bytes_mut.extract_to(align + 1);
327        bytes_mut[..raw.len()].copy_from_slice(&raw);
328        let unaligned_bytes = bytes_mut.extract_to(raw.len());
329
330        let column: Column<i32> = Column::from_bytes(unaligned_bytes);
331        assert!(matches!(column, Column::Align(_)));
332        assert_eq!(
333            column.borrow().into_index_iter().collect::<Vec<_>>(),
334            vec![&1, &2, &3]
335        );
336    }
337}
mz_timely_util/columnar.rs

mz_timely_util/
columnar.rs
