Enum MergeState 

enum MergeState<B: Batch> {
    Vacant,
    Single(Option<B>),
    Double(MergeVariant<B>),
}

Describes the state of a layer.

A layer can be empty, contain a single batch, or contain a pair of batches that are in the process of merging into a batch for the next layer.

Variants

Vacant

An empty layer, containing no updates.

Single(Option<B>)

A layer containing a single batch.

The None variant is used to represent a structurally empty batch present to ensure the progress of maintenance work.

Double(MergeVariant<B>)

A layer containing two batches, in the process of merging.

Implementations

impl<B: Batch<Time: Eq>> MergeState<B>

fn len(&self) -> usize

The number of actual updates contained in the level.

fn is_vacant(&self) -> bool

True only for the MergeState::Vacant variant.

fn is_single(&self) -> bool

True only for the MergeState::Single variant.

fn is_double(&self) -> bool

True only for the MergeState::Double variant.

fn complete(&mut self) -> Option<(B, Option<(B, B)>)>

Immediately complete any merge.

The result is either a batch, if there is a non-trivial batch to return or None if there is no meaningful batch to return. This does not distinguish between Vacant entries and structurally empty batches, which should be done with the is_complete() method.

There is the additional option of input batches.

fn is_complete(&mut self) -> bool

True iff the layer is a complete merge, ready for extraction.

fn work(&mut self, fuel: &mut isize)

Performs a bounded amount of work towards a merge.

If the merge completes, the resulting batch is returned. If a batch is returned, it is the obligation of the caller to correctly install the result.

fn take(&mut self) -> Self

Extract the merge state, typically temporarily.

fn begin_merge( batch1: Option<B>, batch2: Option<B>, compaction_frontier: AntichainRef<'_, B::Time>, ) -> MergeState<B>

Initiates the merge of an “old” batch with a “new” batch.

The upper frontier of the old batch should match the lower frontier of the new batch, with the resulting batch describing their composed interval, from the lower frontier of the old batch to the upper frontier of the new batch.

Either batch may be None which corresponds to a structurally empty batch whose upper and lower froniers are equal. This option exists purely for bookkeeping purposes, and no computation is performed to merge the two batches.