Enum WriteCoalescing 

#[non_exhaustive]
pub enum WriteCoalescing {
    ByKey,
    KeepEveryWrite,
}

How a store queues writes that arrive while its ingest is busy.

For the same writes in a batch, both publish the same rows, change highlights and their directions, fading removals, pinned rows and progress, and the same ChangeSet, except that ChangeSet::updated names a row once for writes merged into one entry instead of once per write. They differ in what a stream costs: the queue’s memory and the ingest’s work grow with the number of keys written (Self::ByKey) or with the number of writes (Self::KeepEveryWrite) between two batches. Neither pushes back on producers: a stream of new keys, or an ingest that falls behind, still grows the queue.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

ByKey

An upsert of a key whose upsert still waits for the ingest takes that one’s place in the queue, so a stream that outruns the ingest queues one entry per key, not per write. The writer diffs the new row against the waiting one (GridRow::changed_columns and GridRow::change_direction), so the ingest highlights each change as if it had applied every write. remove, mark_changed, replace_all, clear and the end of a reload are barriers: an upsert after one never merges into a write before it.

KeepEveryWrite

Every write waits in the queue in turn: under a stream faster than the ingest the queue grows with the event rate.

Trait Implementations

impl Clone for WriteCoalescing

fn clone(&self) -> WriteCoalescing

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for WriteCoalescing

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for WriteCoalescing

fn default() -> WriteCoalescing

Returns the “default value” for a type.

impl PartialEq for WriteCoalescing

fn eq(&self, other: &WriteCoalescing) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for WriteCoalescing

impl Eq for WriteCoalescing

impl StructuralPartialEq for WriteCoalescing