Enum TimestampBound

pub enum TimestampBound {
    Strong,
    ReadTimestamp(SystemTime),
    MinReadTimestamp(SystemTime),
    ExactStaleness(Duration),
    MaxStaleness(Duration),
}

Specifies the bounds withing wich to make reads in Spanner.

See the Spanner Documentation

Variants

Strong

Read at a timestamp where all previously committed transactions are visible.

Strong reads are guaranteed to see the effects of all transactions that have committed before the start of the read. Furthermore, all rows yielded by a single read are consistent with each other – if any part of the read observes a transaction, all parts of the read see the transaction.

ReadTimestamp(SystemTime)

Executes all reads at the given timestamp.

Unlike other modes, reads at a specific timestamp are repeatable; the same read at the same timestamp always returns the same data. If the timestamp is in the future, the read will block until the specified timestamp, modulo the read’s deadline.

Useful for large scale consistent reads such as mapreduces, or for coordinating many reads against a consistent snapshot of the data.

MinReadTimestamp(SystemTime)

Executes all reads at a timestamp >= the provided timestamp.

This is useful for requesting fresher data than some previous read, or data that is fresh enough to observe the effects of some previously committed transaction whose timestamp is known.

ExactStaleness(Duration)

Executes all reads at a timestamp that is ExactStaleness old. The timestamp is chosen soon after the read is started.

Guarantees that all writes that have committed more than the specified number of seconds ago are visible.

MaxStaleness(Duration)

Read data at a timestamp >= now() - MaxStaleness seconds.

Guarantees that all writes that have committed more than the specified number of seconds ago are visible.

Trait Implementations

impl Clone for TimestampBound

fn clone(&self) -> TimestampBound

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for TimestampBound

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

Formats the value using the given formatter.

impl TryFrom<TimestampBound> for TimestampBound

type Error = Error

The type returned in the event of a conversion error.

fn try_from(value: TimestampBound) -> Result<Self, Self::Error>

Performs the conversion.