storage: persist minimum transaction timestamps in intents

Fixes cockroachdb#36089.
Informs cockroachdb#37199.

This commit addresses the second concern from cockroachdb#37199 (comment)
by implementing its suggestion #1.

It augments the TxnMeta struct to begin storing the transaction's
minimum timestamp. This allows pushers to have perfect accuracy
into whether an intent is part of a transaction that can eventually
be committed or whether it has been aborted by any other pusher and
uncommittable.

This allows us to get rid of the false positive cases where a pusher
incorrectly detects that a transaction is still active and begins
waiting on it. In this worst case, this could lead to transactions
waiting for the entire transaction expiration for a contending txn.

Release note: None

pkg/roachpb/data.go

@@ -770,11 +770,12 @@ func MakeTransaction(
 
  return Transaction{
  TxnMeta: enginepb.TxnMeta{
- Key: baseKey,
- ID: u,
- Timestamp: now,
- Priority: MakePriority(userPriority),
- Sequence: 0, // 1-indexed, incremented before each Request
+ Key: baseKey,
+ ID: u,
+ Timestamp: now,
+ MinTimestamp: now,
+ Priority: MakePriority(userPriority),
+ Sequence: 0, // 1-indexed, incremented before each Request
  },
  Name: name,
  LastHeartbeat: now,
@@ -949,13 +950,18 @@ func (t *Transaction) BumpEpoch() {
 // InclusiveTimeBounds returns start and end timestamps such that all intents written as
 // part of this transaction have a timestamp in the interval [start, end].
 func (t *Transaction) InclusiveTimeBounds() (hlc.Timestamp, hlc.Timestamp) {
- min := t.OrigTimestamp
+ min := t.MinTimestamp
  max := t.Timestamp
- if t.Epoch != 0 && t.EpochZeroTimestamp != (hlc.Timestamp{}) {
- if min.Less(t.EpochZeroTimestamp) {
- panic(fmt.Sprintf("orig timestamp %s less than epoch zero %s", min, t.EpochZeroTimestamp))
+ if min.IsEmpty() {
+ // Backwards compatibility with pre-v19.2 nodes.
+ // TODO(nvanbenschoten): Remove in v20.1.
+ min = t.OrigTimestamp
+ if t.Epoch != 0 && t.EpochZeroTimestamp != (hlc.Timestamp{}) {
+ if min.Less(t.EpochZeroTimestamp) {
+ panic(fmt.Sprintf("orig timestamp %s less than epoch zero %s", min, t.EpochZeroTimestamp))
+ }
+ min = t.EpochZeroTimestamp
  }
- min = t.EpochZeroTimestamp
  }
  return min, max
 }
@@ -1001,6 +1007,20 @@ func (t *Transaction) Update(o *Transaction) {
  t.MaxTimestamp.Forward(o.MaxTimestamp)
  t.RefreshedTimestamp.Forward(o.RefreshedTimestamp)
 
+ // On update, set lower bound timestamps to the minimum seen by either txn.
+ // These shouldn't differ unless one of them is empty, but we're careful
+ // anyway.
+ if t.MinTimestamp == (hlc.Timestamp{}) {
+ t.MinTimestamp = o.MinTimestamp
+ } else if o.MinTimestamp != (hlc.Timestamp{}) {
+ t.MinTimestamp.Backward(o.MinTimestamp)
+ }
+ if t.EpochZeroTimestamp == (hlc.Timestamp{}) {
+ t.EpochZeroTimestamp = o.EpochZeroTimestamp
+ } else if o.EpochZeroTimestamp != (hlc.Timestamp{}) {
+ t.EpochZeroTimestamp.Backward(o.EpochZeroTimestamp)
+ }
+
  // Absorb the collected clock uncertainty information.
  for _, v := range o.ObservedTimestamps {
  t.UpdateObservedTimestamp(v.NodeID, v.Timestamp)
@@ -1016,12 +1036,6 @@ func (t *Transaction) Update(o *Transaction) {
  if len(o.InFlightWrites) > 0 {
  t.InFlightWrites = o.InFlightWrites
  }
- // On update, set epoch zero timestamp to the minimum seen by either txn.
- if o.EpochZeroTimestamp != (hlc.Timestamp{}) {
- if t.EpochZeroTimestamp == (hlc.Timestamp{}) || o.EpochZeroTimestamp.Less(t.EpochZeroTimestamp) {
- t.EpochZeroTimestamp = o.EpochZeroTimestamp
- }
- }
 }
 
 // UpgradePriority sets transaction priority to the maximum of current
@@ -1051,9 +1065,9 @@ func (t Transaction) String() string {
  fmt.Fprintf(&buf, "%q ", t.Name)
  }
  fmt.Fprintf(&buf, "id=%s key=%s rw=%t pri=%.8f stat=%s epo=%d "+
- "ts=%s orig=%s max=%s wto=%t seq=%d",
+ "ts=%s orig=%s min=%s max=%s wto=%t seq=%d",
  t.Short(), Key(t.Key), t.IsWriting(), floatPri, t.Status, t.Epoch, t.Timestamp,
- t.OrigTimestamp, t.MaxTimestamp, t.WriteTooOld, t.Sequence)
+ t.OrigTimestamp, t.MinTimestamp, t.MaxTimestamp, t.WriteTooOld, t.Sequence)
  if ni := len(t.IntentSpans); t.Status != PENDING && ni > 0 {
  fmt.Fprintf(&buf, " int=%d", ni)
  }
@@ -1075,9 +1089,9 @@ func (t Transaction) SafeMessage() string {
  fmt.Fprintf(&buf, "%q ", t.Name)
  }
  fmt.Fprintf(&buf, "id=%s rw=%t pri=%.8f stat=%s epo=%d "+
- "ts=%s orig=%s max=%s wto=%t seq=%d",
+ "ts=%s orig=%s min=%s max=%s wto=%t seq=%d",
  t.Short(), t.IsWriting(), floatPri, t.Status, t.Epoch, t.Timestamp,
- t.OrigTimestamp, t.MaxTimestamp, t.WriteTooOld, t.Sequence)
+ t.OrigTimestamp, t.MinTimestamp, t.MaxTimestamp, t.WriteTooOld, t.Sequence)
  if ni := len(t.IntentSpans); t.Status != PENDING && ni > 0 {
  fmt.Fprintf(&buf, " int=%d", ni)
  }