mz_timely_util/containers.rs
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// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License in the LICENSE file at the
// root of this repository, or online at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//! Reusable containers.
use std::hash::Hash;
use columnar::Columnar;
use differential_dataflow::trace::implementations::merge_batcher::{ColMerger, MergeBatcher};
use differential_dataflow::Hashable;
use timely::container::columnation::TimelyStack;
pub mod stack;
pub(crate) use alloc::alloc_aligned_zeroed;
pub use alloc::{enable_columnar_lgalloc, set_enable_columnar_lgalloc};
pub use builder::ColumnBuilder;
pub use container::Column;
pub use provided_builder::ProvidedBuilder;
mod alloc {
use mz_ore::region::Region;
/// Allocate a region of memory with a capacity of at least `len` that is properly aligned
/// and zeroed. The memory in Regions is always aligned to its content type.
#[inline]
pub(crate) fn alloc_aligned_zeroed<T: bytemuck::AnyBitPattern>(len: usize) -> Region<T> {
if enable_columnar_lgalloc() {
Region::new_auto_zeroed(len)
} else {
Region::new_heap_zeroed(len)
}
}
thread_local! {
static ENABLE_COLUMNAR_LGALLOC: std::cell::Cell<bool> = const { std::cell::Cell::new(false) };
}
/// Returns `true` if columnar allocations should come from lgalloc.
#[inline]
pub fn enable_columnar_lgalloc() -> bool {
ENABLE_COLUMNAR_LGALLOC.get()
}
/// Set whether columnar allocations should come from lgalloc. Applies to future allocations.
pub fn set_enable_columnar_lgalloc(enabled: bool) {
ENABLE_COLUMNAR_LGALLOC.set(enabled);
}
}
mod container {
use columnar::bytes::{EncodeDecode, Sequence};
use columnar::common::IterOwn;
use columnar::Columnar;
use columnar::Container as _;
use columnar::{Clear, FromBytes, Index, Len};
use mz_ore::region::Region;
use timely::bytes::arc::Bytes;
use timely::container::PushInto;
use timely::dataflow::channels::ContainerBytes;
use timely::Container;
/// A container based on a columnar store, encoded in aligned bytes.
///
/// The type can represent typed data, bytes from Timely, or an aligned allocation. The name
/// is singular to express that the preferred format is [`Column::Align`]. The [`Column::Typed`]
/// variant is used to construct the container, and it owns potentially multiple columns of data.
pub enum Column<C: Columnar> {
/// The typed variant of the container.
Typed(C::Container),
/// The binary variant of the container.
Bytes(Bytes),
/// Relocated, aligned binary data, if `Bytes` doesn't work for some reason.
///
/// Reasons could include misalignment, cloning of data, or wanting
/// to release the `Bytes` as a scarce resource.
Align(Region<u64>),
}
impl<C: Columnar> Column<C> {
/// Borrows the container as a reference.
fn borrow(&self) -> <C::Container as columnar::Container<C>>::Borrowed<'_> {
match self {
Column::Typed(t) => t.borrow(),
Column::Bytes(b) => {
<<C::Container as columnar::Container<C>>::Borrowed<'_>>::from_bytes(
&mut Sequence::decode(bytemuck::cast_slice(b)),
)
}
Column::Align(a) => {
<<C::Container as columnar::Container<C>>::Borrowed<'_>>::from_bytes(
&mut Sequence::decode(a),
)
}
}
}
}
impl<C: Columnar> Default for Column<C> {
fn default() -> Self {
Self::Typed(Default::default())
}
}
impl<C: Columnar> Clone for Column<C>
where
C::Container: Clone,
{
fn clone(&self) -> Self {
match self {
// Typed stays typed, although we would have the option to move to aligned data.
// If we did it might be confusing why we couldn't push into a cloned column.
Column::Typed(t) => Column::Typed(t.clone()),
Column::Bytes(b) => {
assert_eq!(b.len() % 8, 0);
let mut alloc: Region<u64> = super::alloc_aligned_zeroed(b.len() / 8);
bytemuck::cast_slice_mut(&mut alloc[..]).copy_from_slice(&b[..]);
Self::Align(alloc)
}
Column::Align(a) => {
let mut alloc = super::alloc_aligned_zeroed(a.len());
alloc.extend_from_slice(&a[..]);
Column::Align(alloc)
}
}
}
}
impl<C: Columnar> Container for Column<C> {
type ItemRef<'a> = C::Ref<'a>;
type Item<'a> = C::Ref<'a>;
fn len(&self) -> usize {
self.borrow().len()
}
// This sets the `Bytes` variant to be an empty `Typed` variant, appropriate for pushing into.
fn clear(&mut self) {
match self {
Column::Typed(t) => t.clear(),
Column::Bytes(_) | Column::Align(_) => *self = Column::Typed(Default::default()),
}
}
type Iter<'a> = IterOwn<<C::Container as columnar::Container<C>>::Borrowed<'a>>;
fn iter(&self) -> Self::Iter<'_> {
self.borrow().into_iter()
}
type DrainIter<'a> = IterOwn<<C::Container as columnar::Container<C>>::Borrowed<'a>>;
fn drain(&mut self) -> Self::DrainIter<'_> {
self.borrow().into_iter()
}
}
impl<C: Columnar, T> PushInto<T> for Column<C>
where
C::Container: columnar::Push<T>,
{
#[inline]
fn push_into(&mut self, item: T) {
use columnar::Push;
match self {
Column::Typed(t) => t.push(item),
Column::Align(_) | Column::Bytes(_) => {
// We really oughtn't be calling this in this case.
// We could convert to owned, but need more constraints on `C`.
unimplemented!("Pushing into Column::Bytes without first clearing");
}
}
}
}
impl<C: Columnar> ContainerBytes for Column<C> {
fn from_bytes(bytes: Bytes) -> Self {
// Our expectation / hope is that `bytes` is `u64` aligned and sized.
// If the alignment is borked, we can relocate. If the size is borked,
// not sure what we do in that case. An incorrect size indicates a problem
// of `into_bytes`, or a failure of the communication layer, both of which
// are unrecoverable.
assert_eq!(bytes.len() % 8, 0);
if let Ok(_) = bytemuck::try_cast_slice::<_, u64>(&bytes) {
Self::Bytes(bytes)
} else {
// We failed to cast the slice, so we'll reallocate.
let mut alloc: Region<u64> = super::alloc_aligned_zeroed(bytes.len() / 8);
bytemuck::cast_slice_mut(&mut alloc[..]).copy_from_slice(&bytes[..]);
Self::Align(alloc)
}
}
fn length_in_bytes(&self) -> usize {
match self {
Column::Typed(t) => Sequence::length_in_bytes(&t.borrow()),
Column::Bytes(b) => b.len(),
Column::Align(a) => 8 * a.len(),
}
}
fn into_bytes<W: ::std::io::Write>(&self, writer: &mut W) {
match self {
Column::Typed(t) => Sequence::write(writer, &t.borrow()).unwrap(),
Column::Bytes(b) => writer.write_all(b).unwrap(),
Column::Align(a) => writer.write_all(bytemuck::cast_slice(a)).unwrap(),
}
}
}
}
mod builder {
use std::collections::VecDeque;
use columnar::bytes::{EncodeDecode, Sequence};
use columnar::{Clear, Columnar, Len, Push};
use timely::container::PushInto;
use timely::container::{ContainerBuilder, LengthPreservingContainerBuilder};
use crate::containers::Column;
/// A container builder for `Column<C>`.
pub struct ColumnBuilder<C: Columnar> {
/// Container that we're writing to.
current: C::Container,
/// Finished container that we presented to callers of extract/finish.
///
/// We don't recycle the column because for extract, it's not typed, and after calls
/// to finish it'll be `None`.
finished: Option<Column<C>>,
/// Completed containers pending to be sent.
pending: VecDeque<Column<C>>,
}
impl<C: Columnar, T> PushInto<T> for ColumnBuilder<C>
where
C::Container: Push<T>,
{
#[inline]
fn push_into(&mut self, item: T) {
self.current.push(item);
// If there is less than 10% slop with 2MB backing allocations, mint a container.
use columnar::Container;
let words = Sequence::length_in_words(&self.current.borrow());
let round = (words + ((1 << 18) - 1)) & !((1 << 18) - 1);
if round - words < round / 10 {
/// Move the contents from `current` to an aligned allocation, and push it to `pending`.
/// The contents must fit in `round` words (u64).
#[cold]
fn outlined_align<C>(
current: &mut C::Container,
round: usize,
pending: &mut VecDeque<Column<C>>,
) where
C: Columnar,
{
let mut alloc = super::alloc_aligned_zeroed(round);
let writer = std::io::Cursor::new(bytemuck::cast_slice_mut(&mut alloc[..]));
Sequence::write(writer, ¤t.borrow()).unwrap();
pending.push_back(Column::Align(alloc));
current.clear();
}
outlined_align(&mut self.current, round, &mut self.pending);
}
}
}
impl<C: Columnar> Default for ColumnBuilder<C> {
fn default() -> Self {
ColumnBuilder {
current: Default::default(),
finished: None,
pending: Default::default(),
}
}
}
impl<C: Columnar> ContainerBuilder for ColumnBuilder<C>
where
C::Container: Clone,
{
type Container = Column<C>;
#[inline]
fn extract(&mut self) -> Option<&mut Self::Container> {
if let Some(container) = self.pending.pop_front() {
self.finished = Some(container);
self.finished.as_mut()
} else {
None
}
}
#[inline]
fn finish(&mut self) -> Option<&mut Self::Container> {
if !self.current.is_empty() {
self.pending
.push_back(Column::Typed(std::mem::take(&mut self.current)));
}
self.finished = self.pending.pop_front();
self.finished.as_mut()
}
}
impl<C: Columnar> LengthPreservingContainerBuilder for ColumnBuilder<C> where C::Container: Clone {}
}
/// A batcher for columnar storage.
pub type Col2ValBatcher<K, V, T, R> = MergeBatcher<
Column<((K, V), T, R)>,
batcher::Chunker<TimelyStack<((K, V), T, R)>>,
ColMerger<(K, V), T, R>,
>;
pub type Col2KeyBatcher<K, T, R> = Col2ValBatcher<K, (), T, R>;
/// An exchange function for columnar tuples of the form `((K, V), T, D)`. Rust has a hard
/// time to figure out the lifetimes of the elements when specified as a closure, so we rather
/// specify it as a function.
#[inline(always)]
pub fn columnar_exchange<K, V, T, D>(((k, _), _, _): &<((K, V), T, D) as Columnar>::Ref<'_>) -> u64
where
K: Columnar,
for<'a> K::Ref<'a>: Hash,
V: Columnar,
D: Columnar,
T: Columnar,
{
k.hashed()
}
/// Types for consolidating, merging, and extracting columnar update collections.
pub mod batcher {
use std::collections::VecDeque;
use columnar::Columnar;
use differential_dataflow::difference::Semigroup;
use timely::container::{ContainerBuilder, PushInto};
use timely::Container;
use crate::containers::Column;
#[derive(Default)]
pub struct Chunker<C> {
/// Buffer into which we'll consolidate.
///
/// Also the buffer where we'll stage responses to `extract` and `finish`.
/// When these calls return, the buffer is available for reuse.
target: C,
/// Consolidated buffers ready to go.
ready: VecDeque<C>,
}
impl<C: Container + Clone + 'static> ContainerBuilder for Chunker<C> {
type Container = C;
fn extract(&mut self) -> Option<&mut Self::Container> {
if let Some(ready) = self.ready.pop_front() {
self.target = ready;
Some(&mut self.target)
} else {
None
}
}
fn finish(&mut self) -> Option<&mut Self::Container> {
self.extract()
}
}
impl<'a, D, T, R, C2> PushInto<&'a mut Column<(D, T, R)>> for Chunker<C2>
where
D: Columnar,
for<'b> D::Ref<'b>: Ord + Copy,
T: Columnar,
for<'b> T::Ref<'b>: Ord + Copy,
R: Columnar + Semigroup + for<'b> Semigroup<R::Ref<'b>>,
for<'b> R::Ref<'b>: Ord,
C2: Container + for<'b> PushInto<&'b (D, T, R)>,
{
fn push_into(&mut self, container: &'a mut Column<(D, T, R)>) {
// Sort input data
// TODO: consider `Vec<usize>` that we retain, containing indexes.
let mut permutation = Vec::with_capacity(container.len());
permutation.extend(container.drain());
permutation.sort();
self.target.clear();
// Iterate over the data, accumulating diffs for like keys.
let mut iter = permutation.drain(..);
if let Some((data, time, diff)) = iter.next() {
let mut owned_data = D::into_owned(data);
let mut owned_time = T::into_owned(time);
let mut prev_data = data;
let mut prev_time = time;
let mut prev_diff = <R as Columnar>::into_owned(diff);
for (data, time, diff) in iter {
if (&prev_data, &prev_time) == (&data, &time) {
prev_diff.plus_equals(&diff);
} else {
if !prev_diff.is_zero() {
D::copy_from(&mut owned_data, prev_data);
T::copy_from(&mut owned_time, prev_time);
let tuple = (owned_data, owned_time, prev_diff);
self.target.push_into(&tuple);
(owned_data, owned_time, prev_diff) = tuple;
}
prev_data = data;
prev_time = time;
R::copy_from(&mut prev_diff, diff);
}
}
if !prev_diff.is_zero() {
D::copy_from(&mut owned_data, prev_data);
T::copy_from(&mut owned_time, prev_time);
let tuple = (owned_data, owned_time, prev_diff);
self.target.push_into(&tuple);
}
}
if !self.target.is_empty() {
self.ready.push_back(std::mem::take(&mut self.target));
}
}
}
}
mod provided_builder {
use timely::container::ContainerBuilder;
use timely::Container;
/// A container builder that doesn't support pushing elements, and is only suitable for pushing
/// whole containers at Timely sessions. See [`give_container`] for more information.
///
/// [`give_container`]: timely::dataflow::channels::pushers::buffer::Session::give_container
pub struct ProvidedBuilder<C> {
_marker: std::marker::PhantomData<C>,
}
impl<C> Default for ProvidedBuilder<C> {
fn default() -> Self {
Self {
_marker: std::marker::PhantomData,
}
}
}
impl<C: Container + Clone + 'static> ContainerBuilder for ProvidedBuilder<C> {
type Container = C;
#[inline(always)]
fn extract(&mut self) -> Option<&mut Self::Container> {
None
}
#[inline(always)]
fn finish(&mut self) -> Option<&mut Self::Container> {
None
}
}
}