differential_dataflow::trace::implementations::spine_fueled

Trait SpineBatch

pub trait SpineBatch: Sized {
    type Time: Timestamp + Lattice;
    type Merger: Merger<Self>;

    // Required method
    fn len(&self) -> usize;
}

Expand description

The requirements this spine imposes on the batches its spans carry.

These are opinions of this spine, not properties of batches in general: a batch must support progressive (fuel-limited) merging through a Merger, and must report its size, which drives the spine’s geometric layering and its logging.

Required Associated Types§

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type Time: Timestamp + Lattice

The timestamp type of the batch’s updates.

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type Merger: Merger<Self>

A type used to progressively merge batches.

Required Methods§

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fn len(&self) -> usize

The number of updates in the batch.

A span with nothing in it is meant to carry no batch at all rather than an empty one, so this should be positive. The spine does not rely on that: it asks this method rather than asking whether a span carries a batch, so a producer that hands it an empty batch costs an extra merge rather than behaving differently from the absent case.