Module differential_dataflow::operators::arrange::arrangement [−][src]
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).
Structs
| Arranged | An arranged collection of |
Traits
| Arrange | A type that can be arranged into a trace of type |
| ArrangeByKey | Arranges something as |
| ArrangeBySelf | Arranges something as |