Struct ReadHold

pub struct ReadHold<T: TimelyTimestamp> {
    id: GlobalId,
    since: Antichain<T>,
    change_tx: ChangeTx<T>,
}

Token that represents a hold on a collection. This prevents the since of the collection from progressing beyond the hold. In other words, it cannot become true that our hold is less_than the since.

This ReadHold is safe to drop. The installed read hold will be returned to the issuer behind the scenes.

Fields

id: GlobalId

Identifies that collection that we have a hold on.

since: Antichain<T>

The times at which we hold.

change_tx: ChangeTx<T>

For communicating changes to this read hold back to whoever issued it.

Implementations

impl<T: TimelyTimestamp> ReadHold<T>

pub fn new(id: GlobalId, since: Antichain<T>, change_tx: ChangeTx<T>) -> Self

pub fn with_channel( id: GlobalId, since: Antichain<T>, channel_tx: UnboundedSender<(GlobalId, ChangeBatch<T>)>, ) -> Self

pub fn id(&self) -> GlobalId

Returns the GlobalId of the collection that this ReadHold is for.

pub fn since(&self) -> &Antichain<T>

Returns the frontier at which this ReadHold is holding back the since of the collection identified by id. This does not mean that the overall since of the collection is what we report here. Only that it is at least held back to the reported frontier by this read hold.

pub fn merge_assign(&mut self, other: ReadHold<T>)

Merges other into self, keeping the overall read hold.

Panics

Panics when trying to merge a ReadHold for a different collection (different GlobalId).

pub fn try_downgrade( &mut self, frontier: Antichain<T>, ) -> Result<(), ReadHoldDowngradeError<T>>

Downgrades self to the given frontier. Returns Err when the new frontier is less_than the frontier at which this ReadHold is holding.

pub fn release(&mut self)

Release this read hold.

Trait Implementations

impl<T: TimelyTimestamp> Clone for ReadHold<T>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: TimelyTimestamp> Debug for ReadHold<T>

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

Formats the value using the given formatter.

impl<T: TimelyTimestamp> Drop for ReadHold<T>

fn drop(&mut self)

Executes the destructor for this type.