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MVCC: Add a few comments

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This commit is contained in:
Jussi Saurio
2025-02-08 10:20:48 +02:00
parent fab105c10c
commit 791255fd8c
1 changed files with 4 additions and 0 deletions
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4
core/mvcc/database/mod.rs
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@@ -58,7 +58,9 @@ impl<T> LogRecord<T> {
/// versions switch to tracking timestamps.
#[derive(Clone, Debug, PartialEq, PartialOrd)]
enum TxTimestampOrID {
/// A committed transaction's timestamp.
Timestamp(u64),
/// The ID of a non-committed transaction.
TxID(TxID),
}
@@ -571,6 +573,7 @@ impl<Clock: LogicalClock, T: Sync + Send + Clone + Debug + 'static> MvStore<Cloc
if let TxTimestampOrID::TxID(id) = row_version.begin {
if id == tx_id {
// New version is valid STARTING FROM committing transaction's end timestamp
// See diagram on page 299: https://www.cs.cmu.edu/~15721-f24/papers/Hekaton.pdf
row_version.begin = TxTimestampOrID::Timestamp(end_ts);
self.insert_version_raw(
&mut log_record.row_versions,
@@ -581,6 +584,7 @@ impl<Clock: LogicalClock, T: Sync + Send + Clone + Debug + 'static> MvStore<Cloc
if let Some(TxTimestampOrID::TxID(id)) = row_version.end {
if id == tx_id {
// New version is valid UNTIL committing transaction's end timestamp
// See diagram on page 299: https://www.cs.cmu.edu/~15721-f24/papers/Hekaton.pdf
row_version.end = Some(TxTimestampOrID::Timestamp(end_ts));
self.insert_version_raw(
&mut log_record.row_versions,