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use std::time::Duration;
use std::time::SystemTime;
use google_api_proto::google::spanner::v1 as proto;
/// Specifies the bounds withing wich to make reads in Spanner.
///
/// See [the Spanner Documentation](https://cloud.google.com/spanner/docs/reference/rpc/google.spanner.v1#google.spanner.v1.TransactionOptions.ReadOnly)
#[derive(Clone, Debug)]
pub enum TimestampBound {
/// 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.
Strong,
/// 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.
ReadTimestamp(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.
MinReadTimestamp(SystemTime),
/// 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.
ExactStaleness(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.
MaxStaleness(Duration),
}
impl TryFrom<TimestampBound> for proto::transaction_options::read_only::TimestampBound {
type Error = super::Error;
fn try_from(value: TimestampBound) -> Result<Self, Self::Error> {
match value {
TimestampBound::Strong => {
Ok(proto::transaction_options::read_only::TimestampBound::Strong(true))
}
TimestampBound::ReadTimestamp(timestamp) => Ok(
proto::transaction_options::read_only::TimestampBound::ReadTimestamp(
timestamp.into(),
),
),
TimestampBound::MinReadTimestamp(timestamp) => Ok(
proto::transaction_options::read_only::TimestampBound::MinReadTimestamp(
timestamp.into(),
),
),
TimestampBound::MaxStaleness(duration) => Ok(
proto::transaction_options::read_only::TimestampBound::MaxStaleness(
duration
.try_into()
.map_err(|_| super::Error::Client(format!("invalid bound {duration:?}")))?,
),
),
TimestampBound::ExactStaleness(duration) => Ok(
proto::transaction_options::read_only::TimestampBound::ExactStaleness(
duration
.try_into()
.map_err(|_| super::Error::Client(format!("invalid bound {duration:?}")))?,
),
),
}
}
}
#[derive(Clone, Debug)]
pub(crate) enum TransactionSelector {
SingleUse(Option<TimestampBound>),
Id(Transaction),
Begin,
}
impl TryFrom<TransactionSelector> for proto::TransactionSelector {
type Error = super::Error;
fn try_from(value: TransactionSelector) -> Result<Self, Self::Error> {
match value {
TransactionSelector::SingleUse(bound) => Ok(proto::TransactionSelector {
selector: Some(proto::transaction_selector::Selector::SingleUse(
proto::TransactionOptions {
mode: Some(proto::transaction_options::Mode::ReadOnly(
proto::transaction_options::ReadOnly {
return_read_timestamp: false,
timestamp_bound: match bound {
Some(bound) => Some(bound.try_into()?),
None => None,
},
},
)),
},
)),
}),
TransactionSelector::Id(tx) => Ok(proto::TransactionSelector {
selector: Some(proto::transaction_selector::Selector::Id(tx.spanner_tx.id)),
}),
TransactionSelector::Begin => Ok(proto::TransactionSelector {
selector: Some(proto::transaction_selector::Selector::Begin(
proto::TransactionOptions {
mode: Some(proto::transaction_options::Mode::ReadWrite(
proto::transaction_options::ReadWrite {},
)),
},
)),
}),
}
}
}
#[derive(Debug, Clone)]
pub(crate) struct Transaction {
spanner_tx: proto::Transaction,
}
impl Transaction {
pub(crate) fn id(&self) -> &prost::bytes::Bytes {
&self.spanner_tx.id
}
}
impl From<proto::Transaction> for Transaction {
fn from(spanner_tx: proto::Transaction) -> Self {
Transaction { spanner_tx }
}
}
impl From<Transaction> for proto::Transaction {
fn from(tx: Transaction) -> Self {
tx.spanner_tx
}
}