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//! Arranges a collection into a re-usable trace structure.
//!
//! The `arrange` operator applies to a differential dataflow `Collection` and returns an `Arranged`
//! structure, provides access to both an indexed form of accepted updates as well as a stream of
//! batches of newly arranged updates.
//!
//! Several operators (`join`, `group`, and `cogroup`, among others) are implemented against `Arranged`,
//! and can be applied directly to arranged data instead of the collection. Internally, the operators
//! will borrow the shared state, and listen on the timely stream for shared batches of data. The
//! resources to index the collection---communication, computation, and memory---are spent only once,
//! and only one copy of the index needs to be maintained as the collection changes.
//!
//! The arranged collection is stored in a trace, whose append-only operation means that it is safe to
//! share between the single `arrange` writer and multiple readers. Each reader is expected to interrogate
//! the trace only at times for which it knows the trace is complete, as indicated by the frontiers on its
//! incoming channels. Failing to do this is "safe" in the Rust sense of memory safety, but the reader may
//! see ill-defined data at times for which the trace is not complete. (All current implementations
//! commit only completed data to the trace).
use std::rc::{Rc, Weak};
use std::cell::RefCell;
use std::default::Default;
use std::collections::VecDeque;
use timely::dataflow::operators::{Enter, Map};
use timely::order::{PartialOrder, TotalOrder};
use timely::dataflow::{Scope, Stream};
use timely::dataflow::operators::generic::{Operator, source};
use timely::dataflow::channels::pact::{Pipeline, Exchange};
use timely::progress::Timestamp;
use timely::progress::frontier::Antichain;
use timely::dataflow::operators::Capability;
use timely_sort::Unsigned;
use ::{Data, Diff, Collection, AsCollection, Hashable};
use lattice::Lattice;
use trace::{Trace, TraceReader, Batch, BatchReader, Batcher, Cursor};
use trace::implementations::ord::OrdValSpine as DefaultValTrace;
use trace::implementations::ord::OrdKeySpine as DefaultKeyTrace;
use trace::wrappers::enter::{TraceEnter, BatchEnter};
use trace::wrappers::enter_at::TraceEnter as TraceEnterAt;
use trace::wrappers::enter_at::BatchEnter as BatchEnterAt;
use trace::wrappers::rc::TraceBox;
use trace::wrappers::filter::{TraceFilter, BatchFilter};
/// A trace writer capability.
pub struct TraceWriter<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: Trace<K,V,T,R>, Tr::Batch: Batch<K,V,T,R> {
phantom: ::std::marker::PhantomData<(K, V, R)>,
trace: Weak<RefCell<TraceBox<K, V, T, R, Tr>>>,
queues: Rc<RefCell<(Vec<T>,Vec<Weak<RefCell<VecDeque<(Vec<T>, Option<(T, Tr::Batch)>)>>>>)>>,
}
impl<K, V, T, R, Tr> TraceWriter<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: Trace<K,V,T,R>, Tr::Batch: Batch<K,V,T,R> {
/// Advances the trace to `frontier`, providing batch data if it exists.
pub fn seal(&mut self, frontier: &[T], data: Option<(T, Tr::Batch)>) {
// push information to each listener that still exists.
let mut borrow = self.queues.borrow_mut();
borrow.0 = frontier.to_vec();
for queue in borrow.1.iter_mut() {
if let Some(mut queue) = queue.upgrade() {
queue.borrow_mut().push_back((frontier.to_vec(), data.clone()));
}
}
borrow.1.retain(|w| w.upgrade().is_some());
// push data to the trace, if it still exists.
if let Some(trace) = self.trace.upgrade() {
if let Some((_time, batch)) = data {
trace.borrow_mut().trace.insert(batch);
}
else if frontier.is_empty() {
trace.borrow_mut().trace.close();
}
else {
// TODO: Frontier progress without data and without closing the
// trace should be recorded somewhere, probably in the trace
// itself. This could be using empty batches, which seems a
// bit of a waste, but is perhaps still important to do?
}
}
}
}
impl<K, V, T, R, Tr> Drop for TraceWriter<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: Trace<K,V,T,R>, Tr::Batch: Batch<K,V,T,R> {
fn drop(&mut self) {
// TODO: This method exists in case a TraceWriter is dropped without sealing
// up through the empty frontier. Does this happen? Should it be an
// error to do that sort of thing?
let mut borrow = self.queues.borrow_mut();
for queue in borrow.1.iter_mut() {
queue.upgrade().map(|queue| {
queue.borrow_mut().push_back((Vec::new(), None));
});
}
borrow.1.retain(|w| w.upgrade().is_some());
}
}
/// A `TraceReader` wrapper which can be imported into other dataflows.
///
/// The `TraceAgent` is the default trace type produced by `arranged`, and it can be extracted
/// from the dataflow in which it was defined, and imported into other dataflows.
pub struct TraceAgent<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: TraceReader<K,V,T,R> {
phantom: ::std::marker::PhantomData<(K, V, R)>,
trace: Rc<RefCell<TraceBox<K, V, T, R, Tr>>>,
queues: Weak<RefCell<(Vec<T>,Vec<Weak<RefCell<VecDeque<(Vec<T>, Option<(T, Tr::Batch)>)>>>>)>>,
advance: Vec<T>,
through: Vec<T>,
}
impl<K, V, T, R, Tr> TraceReader<K, V, T, R> for TraceAgent<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: TraceReader<K,V,T,R> {
type Batch = Tr::Batch;
type Cursor = Tr::Cursor;
fn advance_by(&mut self, frontier: &[T]) {
self.trace.borrow_mut().adjust_advance_frontier(&self.advance[..], frontier);
self.advance.clear();
self.advance.extend(frontier.iter().cloned());
}
fn advance_frontier(&mut self) -> &[T] {
&self.advance[..]
}
fn distinguish_since(&mut self, frontier: &[T]) {
self.trace.borrow_mut().adjust_through_frontier(&self.through[..], frontier);
self.through.clear();
self.through.extend(frontier.iter().cloned());
}
fn distinguish_frontier(&mut self) -> &[T] {
&self.through[..]
}
fn cursor_through(&mut self, frontier: &[T]) -> Option<(Tr::Cursor, <Tr::Cursor as Cursor<K, V, T, R>>::Storage)> { self.trace.borrow_mut().trace.cursor_through(frontier) }
fn map_batches<F: FnMut(&Self::Batch)>(&mut self, f: F) { self.trace.borrow_mut().trace.map_batches(f) }
}
impl<K, V, T, R, Tr> TraceAgent<K, V, T, R, Tr>
where T: Timestamp+Lattice, Tr: TraceReader<K,V,T,R> {
/// Creates a new agent from a trace reader.
pub fn new(trace: Tr) -> (Self, TraceWriter<K,V,T,R,Tr>) where Tr: Trace<K,V,T,R>, Tr::Batch: Batch<K,V,T,R> {
let trace = Rc::new(RefCell::new(TraceBox::new(trace)));
let queues = Rc::new(RefCell::new((vec![Default::default()], Vec::new())));
let reader = TraceAgent {
phantom: ::std::marker::PhantomData,
trace: trace.clone(),
queues: Rc::downgrade(&queues),
advance: trace.borrow().advance_frontiers.frontier().to_vec(),
through: trace.borrow().through_frontiers.frontier().to_vec(),
};
let writer = TraceWriter {
phantom: ::std::marker::PhantomData,
trace: Rc::downgrade(&trace),
queues: queues,
};
(reader, writer)
}
/// Attaches a new shared queue to the trace.
///
/// The queue will be immediately populated with existing historical batches from the trace, and until the reference
/// is dropped the queue will receive new batches as produced by the source `arrange` operator.
pub fn new_listener(&mut self) -> Rc<RefCell<VecDeque<(Vec<T>, Option<(T, <Tr as TraceReader<K,V,T,R>>::Batch)>)>>> where T: Default {
// create a new queue for progress and batch information.
let mut new_queue = VecDeque::new();
// add the existing batches from the trace
self.trace.borrow_mut().trace.map_batches(|batch| {
new_queue.push_back((vec![T::default()], Some((T::default(), batch.clone()))));
});
let reference = Rc::new(RefCell::new(new_queue));
// wraps the queue in a ref-counted ref cell and enqueue/return it.
if let Some(queue) = self.queues.upgrade() {
let mut borrow = queue.borrow_mut();
reference.borrow_mut().push_back((borrow.0.clone(), None));
borrow.1.push(Rc::downgrade(&reference));
}
else {
// if the trace is closed, send a final signal.
reference.borrow_mut().push_back((Vec::new(), None));
}
reference
}
}
impl<K, V, T, R, Tr> TraceAgent<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: TraceReader<K,V,T,R> {
/// Copies an existing collection into the supplied scope.
///
/// This method creates an `Arranged` collection that should appear indistinguishable from applying `arrange`
/// directly to the source collection brought into the local scope. The only caveat is that the initial state
/// of the collection is its current state, and updates occur from this point forward. The historical changes
/// the collection experienced in the past are accumulated, and the distinctions from the initial collection
/// are no longer evident.
///
/// The current behavior is that the introduced collection accumulates updates to some times less or equal
/// to `self.advance_frontier()`. There is *not* currently a guarantee that the updates are accumulated *to*
/// the frontier, and the resulting collection history may be weirdly partial until this point. In particular,
/// the historical collection may move through configurations that did not actually occur, even if eventually
/// arriving at the correct collection. This is probably a bug; although we get to the right place in the end,
/// the intermediate computation could do something that the original computation did not, like diverge.
///
/// I would expect the semantics to improve to "updates are advanced to `self.advance_frontier()`", which
/// means the computation will run as if starting from exactly this frontier. It is not currently clear whose
/// responsibility this should be (the trace/batch should only reveal these times, or an operator should know
/// to advance times before using them).
///
/// # Examples
///
/// ```
/// extern crate timely;
/// extern crate differential_dataflow;
///
/// use timely::Configuration;
/// use differential_dataflow::input::Input;
/// use differential_dataflow::operators::arrange::ArrangeBySelf;
/// use differential_dataflow::operators::group::Group;
/// use differential_dataflow::trace::Trace;
/// use differential_dataflow::trace::implementations::ord::OrdValSpine;
/// use differential_dataflow::hashable::OrdWrapper;
///
/// fn main() {
/// ::timely::execute(Configuration::Thread, |worker| {
///
/// // create a first dataflow
/// let mut trace = worker.dataflow::<u32,_,_>(|scope| {
/// // create input handle and collection.
/// scope.new_collection_from(0 .. 10).1
/// .arrange_by_self()
/// .trace
/// });
///
/// // do some work.
/// worker.step();
/// worker.step();
///
/// // create a second dataflow
/// worker.dataflow(move |scope| {
/// trace.import(scope)
/// .group(move |_key, src, dst| dst.push((*src[0].0, 1)));
/// });
///
/// }).unwrap();
/// }
/// ```
pub fn import<G: Scope<Timestamp=T>>(&mut self, scope: &G) -> Arranged<G, K, V, R, TraceAgent<K, V, T, R, Tr>> where T: Timestamp {
let queue = self.new_listener();
let collection = source(scope, "ArrangedSource", move |capability| {
// capabilities the source maintains.
let mut capabilities = vec![capability];
move |output| {
let mut borrow = queue.borrow_mut();
while let Some((frontier, sent)) = borrow.pop_front() {
// if data are associated, send em!
if let Some((time, batch)) = sent {
let delayed =
capabilities
.iter()
.find(|c| c.time().less_equal(&time))
.expect("failed to find capability")
.delayed(&time);
output.session(&delayed).give(batch);
}
// advance capabilities to look like `frontier`.
let mut new_capabilities = Vec::new();
for time in frontier.iter() {
if let Some(cap) = capabilities.iter().find(|c| c.time().less_equal(&time)) {
new_capabilities.push(cap.delayed(&time));
}
else {
panic!("failed to find capability for {:?} in {:?}", time, capabilities);
}
}
capabilities = new_capabilities;
}
}
});
Arranged {
stream: collection,
trace: self.clone(),
}
}
}
impl<K, V, T, R, Tr> Clone for TraceAgent<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: TraceReader<K,V,T,R> {
fn clone(&self) -> Self {
// increase counts for wrapped `TraceBox`.
self.trace.borrow_mut().adjust_advance_frontier(&[], &self.advance[..]);
self.trace.borrow_mut().adjust_through_frontier(&[], &self.through[..]);
TraceAgent {
phantom: ::std::marker::PhantomData,
trace: self.trace.clone(),
queues: self.queues.clone(),
advance: self.advance.clone(),
through: self.through.clone(),
}
}
}
impl<K, V, T, R, Tr> Drop for TraceAgent<K, V, T, R, Tr>
where T: Lattice+Ord+Clone+'static, Tr: TraceReader<K,V,T,R> {
fn drop(&mut self) {
// decrement borrow counts to remove all holds
self.trace.borrow_mut().adjust_advance_frontier(&self.advance[..], &[]);
self.trace.borrow_mut().adjust_through_frontier(&self.through[..], &[]);
}
}
/// An arranged collection of `(K,V)` values.
///
/// An `Arranged` allows multiple differential operators to share the resources (communication,
/// computation, memory) required to produce and maintain an indexed representation of a collection.
pub struct Arranged<G: Scope, K, V, R, T> where G::Timestamp: Lattice+Ord, T: TraceReader<K, V, G::Timestamp, R>+Clone {
/// A stream containing arranged updates.
///
/// This stream contains the same batches of updates the trace itself accepts, so there should
/// be no additional overhead to receiving these records. The batches can be navigated just as
/// the batches in the trace, by key and by value.
pub stream: Stream<G, T::Batch>,
/// A shared trace, updated by the `Arrange` operator and readable by others.
pub trace: T,
// TODO : We might have an `Option<Collection<G, (K, V)>>` here, which `as_collection` sets and
// returns when invoked, so as to not duplicate work with multiple calls to `as_collection`.
}
impl<G: Scope, K, V, R, T> Clone for Arranged<G, K, V, R, T>
where G::Timestamp: Lattice+Ord, T: TraceReader<K, V, G::Timestamp, R>+Clone {
fn clone(&self) -> Self {
Arranged {
stream: self.stream.clone(),
trace: self.trace.clone(),
}
}
}
use ::timely::dataflow::scopes::Child;
use ::timely::progress::timestamp::Refines;
impl<G: Scope, K, V, R, T> Arranged<G, K, V, R, T> where G::Timestamp: Lattice+Ord, T: TraceReader<K, V, G::Timestamp, R>+Clone {
/// Brings an arranged collection into a nested scope.
///
/// This method produces a proxy trace handle that uses the same backing data, but acts as if the timestamps
/// have all been extended with an additional coordinate with the default value. The resulting collection does
/// not vary with the new timestamp coordinate.
pub fn enter<'a, TInner>(&self, child: &Child<'a, G, TInner>)
-> Arranged<Child<'a, G, TInner>, K, V, R, TraceEnter<K, V, G::Timestamp, R, T, TInner>>
where
T::Batch: Clone,
K: 'static,
V: 'static,
G::Timestamp: Clone+Default+'static,
TInner: Refines<G::Timestamp>+Lattice+Timestamp+Clone+Default+'static,
R: 'static,
{
Arranged {
stream: self.stream.enter(child).map(|bw| BatchEnter::make_from(bw)),
trace: TraceEnter::make_from(self.trace.clone()),
}
}
/// Brings an arranged collection into a nested scope.
///
/// This method produces a proxy trace handle that uses the same backing data, but acts as if the timestamps
/// have all been extended with an additional coordinate with the default value. The resulting collection does
/// not vary with the new timestamp coordinate.
pub fn enter_at<'a, TInner, F>(&self, child: &Child<'a, G, TInner>, logic: F)
-> Arranged<Child<'a, G, TInner>, K, V, R, TraceEnterAt<K, V, G::Timestamp, R, T, TInner, F>>
where
T::Batch: Clone,
K: 'static,
V: 'static,
G::Timestamp: Clone+Default+'static,
TInner: Refines<G::Timestamp>+Lattice+Timestamp+Clone+Default+'static,
R: 'static,
F: Fn(&K, &V, &G::Timestamp)->TInner+'static,
{
let logic = Rc::new(logic);
Arranged {
trace: TraceEnterAt::make_from(self.trace.clone(), logic.clone()),
stream: self.stream.enter(child).map(move |bw| BatchEnterAt::make_from(bw, logic.clone())),
}
}
/// Filters an arranged collection.
///
/// This method produces a new arrangement backed by the same shared
/// arrangement as `self`, paired with user-specified logic that can
/// filter by key and value. The resulting collection is restricted
/// to the keys and values that return true under the user predicate.
///
/// # Examples
///
/// ```
/// extern crate timely;
/// extern crate differential_dataflow;
///
/// use differential_dataflow::input::Input;
/// use differential_dataflow::operators::arrange::ArrangeByKey;
///
/// fn main() {
/// ::timely::example(|scope| {
///
/// let arranged =
/// scope.new_collection_from(0 .. 10).1
/// .map(|x| (x, x+1))
/// .arrange_by_key();
///
/// arranged
/// .filter(|k,v| k == v)
/// .as_collection(|k,v| (*k,*v))
/// .assert_empty();
/// });
/// }
/// ```
pub fn filter<F>(&self, logic: F)
-> Arranged<G, K, V, R, TraceFilter<K, V, G::Timestamp, R, T, F>>
where
T::Batch: Clone,
K: 'static,
V: 'static,
G::Timestamp: Clone+Default+'static,
R: 'static,
F: Fn(&K, &V)->bool+'static,
{
let logic = Rc::new(logic);
Arranged {
trace: TraceFilter::make_from(self.trace.clone(), logic.clone()),
stream: self.stream.map(move |bw| BatchFilter::make_from(bw, logic.clone())),
}
}
/// Flattens the stream into a `Collection`.
///
/// The underlying `Stream<G, BatchWrapper<T::Batch>>` is a much more efficient way to access the data,
/// and this method should only be used when the data need to be transformed or exchanged, rather than
/// supplied as arguments to an operator using the same key-value structure.
pub fn as_collection<D: Data, L>(&self, logic: L) -> Collection<G, D, R>
where
R: Diff,
T::Batch: Clone+'static,
K: Clone, V: Clone,
L: Fn(&K, &V) -> D+'static,
{
self.flat_map_ref(move |key, val| Some(logic(key,val)))
}
/// Extracts elements from an arrangement as a collection.
///
/// The supplied logic may produce an iterator over output values, allowing either
/// filtering or flat mapping as part of the extraction.
pub fn flat_map_ref<I, L>(&self, logic: L) -> Collection<G, I::Item, R>
where
R: Diff,
T::Batch: Clone+'static,
K: Clone, V: Clone,
I: IntoIterator,
I::Item: Data,
L: Fn(&K, &V) -> I+'static,
{
self.stream.unary(Pipeline, "AsCollection", move |_,_| move |input, output| {
input.for_each(|time, data| {
let mut session = output.session(&time);
for wrapper in data.iter() {
let batch = &wrapper;
let mut cursor = batch.cursor();
while let Some(key) = cursor.get_key(batch) {
while let Some(val) = cursor.get_val(batch) {
for datum in logic(key, val) {
cursor.map_times(batch, |time, diff| {
session.give((datum.clone(), time.clone(), diff.clone()));
});
}
cursor.step_val(batch);
}
cursor.step_key(batch);
}
}
});
})
.as_collection()
}
/// Report values associated with keys at certain times.
///
/// This method consumes a stream of (key, time) queries and reports the corresponding stream of
/// (key, value, time, diff) accumulations in the `self` trace.
pub fn lookup(&self, queries: &Stream<G, (K, G::Timestamp)>) -> Stream<G, (K, V, G::Timestamp, R)>
where
G::Timestamp: Data+Lattice+Ord+TotalOrder,
K: Data+Hashable,
V: Data,
R: Diff,
T: 'static
{
// while the arrangement is already correctly distributed, the query stream may not be.
let exchange = Exchange::new(move |update: &(K,G::Timestamp)| update.0.hashed().as_u64());
queries.binary_frontier(&self.stream, exchange, Pipeline, "TraceQuery", move |_capability, _info| {
let mut trace = Some(self.trace.clone());
// release `distinguish_since` capability.
trace.as_mut().unwrap().distinguish_since(&[]);
let mut stash = Vec::new();
let mut capability: Option<Capability<G::Timestamp>> = None;
let mut active = Vec::new();
let mut retain = Vec::new();
let mut working: Vec<(G::Timestamp, V, R)> = Vec::new();
let mut working2: Vec<(V, R)> = Vec::new();
move |input1, input2, output| {
input1.for_each(|time, data| {
// if the minimum capability "improves" retain it.
if capability.is_none() || time.time().less_than(capability.as_ref().unwrap().time()) {
capability = Some(time.retain());
}
stash.extend(data.iter().cloned());
});
// drain input2; we will consult `trace` directly.
input2.for_each(|_time, _data| { });
assert_eq!(capability.is_none(), stash.is_empty());
let mut drained = false;
if let Some(capability) = capability.as_mut() {
if !input2.frontier().less_equal(capability.time()) {
for datum in stash.drain(..) {
if !input2.frontier().less_equal(&datum.1) {
active.push(datum);
}
else {
retain.push(datum);
}
}
drained = !active.is_empty();
::std::mem::swap(&mut stash, &mut retain); // retain now the stashed queries.
// sort temp1 by key and then by time.
active.sort_unstable_by(|x,y| x.0.cmp(&y.0));
let (mut cursor, storage) = trace.as_mut().unwrap().cursor();
let mut session = output.session(&capability);
// // V0: Potentially quadratic under load.
// for (key, time) in active.drain(..) {
// cursor.seek_key(&storage, &key);
// if cursor.get_key(&storage) == Some(&key) {
// while let Some(val) = cursor.get_val(&storage) {
// let mut count = R::zero();
// cursor.map_times(&storage, |t, d| if t.less_equal(&time) {
// count = count + d;
// });
// if !count.is_zero() {
// session.give((key.clone(), val.clone(), time.clone(), count));
// }
// cursor.step_val(&storage);
// }
// }
// }
// V1: Stable under load
let mut active_finger = 0;
while active_finger < active.len() {
let key = &active[active_finger].0;
let mut same_key = active_finger;
while active.get(same_key).map(|x| &x.0) == Some(key) {
same_key += 1;
}
cursor.seek_key(&storage, key);
if cursor.get_key(&storage) == Some(key) {
let mut active = &active[active_finger .. same_key];
while let Some(val) = cursor.get_val(&storage) {
cursor.map_times(&storage, |t,d| working.push((t.clone(), val.clone(), d)));
cursor.step_val(&storage);
}
working.sort_by(|x,y| x.0.cmp(&y.0));
for (time, val, diff) in working.drain(..) {
if !active.is_empty() && active[0].1.less_than(&time) {
::trace::consolidate(&mut working2, 0);
while !active.is_empty() && active[0].1.less_than(&time) {
for &(ref val, count) in working2.iter() {
session.give((key.clone(), val.clone(), active[0].1.clone(), count));
}
active = &active[1..];
}
}
working2.push((val, diff));
}
if !active.is_empty() {
::trace::consolidate(&mut working2, 0);
while !active.is_empty() {
for &(ref val, count) in working2.iter() {
let count: R = count;
session.give((key.clone(), val.clone(), active[0].1.clone(), count));
}
active = &active[1..];
}
}
}
active_finger = same_key;
}
active.clear();
}
}
if drained {
if stash.is_empty() { capability = None; }
if let Some(capability) = capability.as_mut() {
let mut min_time = stash[0].1.clone();
for datum in stash[1..].iter() {
if datum.1.less_than(&min_time) {
min_time = datum.1.clone();
}
}
capability.downgrade(&min_time);
}
}
// Determine new frontier on queries that may be issued.
let frontier = [
capability.as_ref().map(|c| c.time().clone()),
input1.frontier().frontier().get(0).cloned(),
].into_iter().cloned().filter_map(|t| t).min();
if let Some(frontier) = frontier {
trace.as_mut().map(|t| t.advance_by(&[frontier]));
}
else {
trace = None;
}
}
})
}
}
/// A type that can be arranged into a trace of type `T`.
///
/// This trait is implemented for appropriately typed collections and all traces that might accommodate them,
/// as well as by arranged data for their corresponding trace type.
pub trait Arrange<G: Scope, K, V, R: Diff>
where
G::Timestamp: Lattice,
{
/// Arranges a stream of `(Key, Val)` updates by `Key`. Accepts an empty instance of the trace type.
///
/// This operator arranges a stream of values into a shared trace, whose contents it maintains.
/// This trace is current for all times marked completed in the output stream, and probing this stream
/// is the correct way to determine that times in the shared trace are committed.
fn arrange<T>(&self) -> Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, T>>
where
T: Trace<K, V, G::Timestamp, R>+'static,
T::Batch: Batch<K, V, G::Timestamp, R>,
{
self.arrange_named("Arrange")
}
/// Arranges a stream of `(Key, Val)` updates by `Key`. Accepts an empty instance of the trace type.
///
/// This operator arranges a stream of values into a shared trace, whose contents it maintains.
/// This trace is current for all times marked completed in the output stream, and probing this stream
/// is the correct way to determine that times in the shared trace are committed.
fn arrange_named<T>(&self, name: &str) -> Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, T>>
where
T: Trace<K, V, G::Timestamp, R>+'static,
T::Batch: Batch<K, V, G::Timestamp, R>;
}
impl<G: Scope, K: Data+Hashable, V: Data, R: Diff> Arrange<G, K, V, R> for Collection<G, (K, V), R>
where
G::Timestamp: Lattice+Ord,
{
fn arrange_named<T>(&self, name: &str) -> Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, T>>
where
T: Trace<K, V, G::Timestamp, R>+'static,
T::Batch: Batch<K, V, G::Timestamp, R>,
{
let mut reader = None;
// fabricate a data-parallel operator using the `unary_notify` pattern.
let stream = {
let reader = &mut reader;
let exchange = Exchange::new(move |update: &((K,V),G::Timestamp,R)| (update.0).0.hashed().as_u64());
self.inner.unary_frontier(exchange, name, move |_capability, _info| {
// Attempt to acquire a logger for arrange events.
let logger = {
let scope = self.scope();
let register = scope.log_register();
register.get::<::logging::DifferentialEvent>("differential/arrange")
};
// Where we will deposit received updates, and from which we extract batches.
let mut batcher = <T::Batch as Batch<K,V,G::Timestamp,R>>::Batcher::new();
// Capabilities for the lower envelope of updates in `batcher`.
let mut capabilities = Antichain::<Capability<G::Timestamp>>::new();
let mut buffer = Vec::new();
let empty_trace = T::new(_info, logger);
let (reader_local, mut writer) = TraceAgent::new(empty_trace);
*reader = Some(reader_local);
move |input, output| {
// As we receive data, we need to (i) stash the data and (ii) keep *enough* capabilities.
// We don't have to keep all capabilities, but we need to be able to form output messages
// when we realize that time intervals are complete.
input.for_each(|cap, data| {
capabilities.insert(cap.retain());
data.swap(&mut buffer);
batcher.push_batch(&mut buffer);
});
// The frontier may have advanced by multiple elements, which is an issue because
// timely dataflow currently only allows one capability per message. This means we
// must pretend to process the frontier advances one element at a time, batching
// and sending smaller bites than we might have otherwise done.
// If there is at least one capability no longer in advance of the input frontier ...
if capabilities.elements().iter().any(|c| !input.frontier().less_equal(c.time())) {
let mut upper = Antichain::new(); // re-used allocation for sealing batches.
// For each capability not in advance of the input frontier ...
for (index, capability) in capabilities.elements().iter().enumerate() {
if !input.frontier().less_equal(capability.time()) {
// Assemble the upper bound on times we can commit with this capabilities.
// We must respect the input frontier, and *subsequent* capabilities, as
// we are pretending to retire the capability changes one by one.
upper.clear();
for time in input.frontier().frontier().iter() {
upper.insert(time.clone());
}
for other_capability in &capabilities.elements()[(index + 1) .. ] {
upper.insert(other_capability.time().clone());
}
// Extract updates not in advance of `upper`.
let batch = batcher.seal(upper.elements());
writer.seal(upper.elements(), Some((capability.time().clone(), batch.clone())));
// send the batch to downstream consumers, empty or not.
output.session(&capabilities.elements()[index]).give(batch);
}
}
// Having extracted and sent batches between each capability and the input frontier,
// we should downgrade all capabilities to match the batcher's lower update frontier.
// This may involve discarding capabilities, which is fine as any new updates arrive
// in messages with new capabilities.
let mut new_capabilities = Antichain::new();
for time in batcher.frontier() {
if let Some(capability) = capabilities.elements().iter().find(|c| c.time().less_equal(time)) {
new_capabilities.insert(capability.delayed(time));
}
else {
panic!("failed to find capability");
}
}
capabilities = new_capabilities;
}
// Announce progress updates.
// TODO: This is very noisy; consider tracking the previous frontier, and issuing an update
// if and when it changes.
writer.seal(&input.frontier().frontier(), None);
}})
};
Arranged { stream: stream, trace: reader.unwrap() }
}
}
impl<G: Scope, K: Data+Hashable, R: Diff> Arrange<G, K, (), R> for Collection<G, K, R>
where
G::Timestamp: Lattice+Ord,
{
fn arrange_named<T>(&self, name: &str) -> Arranged<G, K, (), R, TraceAgent<K, (), G::Timestamp, R, T>>
where
T: Trace<K, (), G::Timestamp, R>+'static,
T::Batch: Batch<K, (), G::Timestamp, R>
{
self.map(|k| (k, ()))
.arrange_named(name)
}
}
// impl<G, K, V, R, T> Arrange<G, K, V, R, T> for Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, T>>
// where
// G: Scope,
// G::Timestamp: Lattice,
// R: Diff,
// T: Trace<K, V, G::Timestamp, R>+Clone+'static,
// T::Batch: Batch<K, V, G::Timestamp, R>
// {
// fn arrange_named(&self, _name: &str) -> Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, T>> {
// (*self).clone()
// }
// }
/// Arranges something as `(Key,Val)` pairs according to a type `T` of trace.
///
/// This arrangement requires `Key: Hashable`, and uses the `hashed()` method to place keys in a hashed
/// map. This can result in many hash calls, and in some cases it may help to first transform `K` to the
/// pair `(u64, K)` of hash value and key.
pub trait ArrangeByKey<G: Scope, K: Data+Hashable, V: Data, R: Diff>
where G::Timestamp: Lattice+Ord {
/// Arranges a collection of `(Key, Val)` records by `Key`.
///
/// This operator arranges a stream of values into a shared trace, whose contents it maintains.
/// This trace is current for all times completed by the output stream, which can be used to
/// safely identify the stable times and values in the trace.
fn arrange_by_key(&self) -> Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, DefaultValTrace<K, V, G::Timestamp, R>>>;
}
impl<G: Scope, K: Data+Hashable, V: Data, R: Diff> ArrangeByKey<G, K, V, R> for Collection<G, (K,V), R>
where G::Timestamp: Lattice+Ord {
fn arrange_by_key(&self) -> Arranged<G, K, V, R, TraceAgent<K, V, G::Timestamp, R, DefaultValTrace<K, V, G::Timestamp, R>>> {
self.arrange()
}
}
/// Arranges something as `(Key, ())` pairs according to a type `T` of trace.
///
/// This arrangement requires `Key: Hashable`, and uses the `hashed()` method to place keys in a hashed
/// map. This can result in many hash calls, and in some cases it may help to first transform `K` to the
/// pair `(u64, K)` of hash value and key.
pub trait ArrangeBySelf<G: Scope, K: Data+Hashable, R: Diff>
where G::Timestamp: Lattice+Ord {
/// Arranges a collection of `Key` records by `Key`.
///
/// This operator arranges a collection of records into a shared trace, whose contents it maintains.
/// This trace is current for all times complete in the output stream, which can be used to safely
/// identify the stable times and values in the trace.
fn arrange_by_self(&self) -> Arranged<G, K, (), R, TraceAgent<K, (), G::Timestamp, R, DefaultKeyTrace<K, G::Timestamp, R>>>;
}
impl<G: Scope, K: Data+Hashable, R: Diff> ArrangeBySelf<G, K, R> for Collection<G, K, R>
where G::Timestamp: Lattice+Ord {
fn arrange_by_self(&self) -> Arranged<G, K, (), R, TraceAgent<K, (), G::Timestamp, R, DefaultKeyTrace<K, G::Timestamp, R>>> {
self.map(|k| (k, ()))
.arrange()
}
}