func (tc *timestampCache) getMax(
start, end roachpb.Key, readTSCache bool,
) (hlc.Timestamp, *uuid.UUID, bool) {
if len(end) == 0 {
end = start.Next()
}
var ok bool
maxTS := tc.lowWater
var maxTxnID *uuid.UUID
cache := tc.wCache
if readTSCache {
cache = tc.rCache
}
for _, o := range cache.GetOverlaps(start, end) {
ce := o.Value.(*cacheValue)
if maxTS.Less(ce.timestamp) {
ok = true
maxTS = ce.timestamp
maxTxnID = ce.txnID
} else if maxTS.Equal(ce.timestamp) && maxTxnID != nil &&
(ce.txnID == nil || *maxTxnID != *ce.txnID) {
maxTxnID = nil
}
}
return maxTS, maxTxnID, ok
}
// add the specified timestamp to the cache as covering the range of
// keys from start to end. If end is nil, the range covers the start
// key only. txnID is nil for no transaction. readTSCache specifies
// whether the command adding this timestamp should update the read
// timestamp; false to update the write timestamp cache.
func (tc *timestampCache) add(
start, end roachpb.Key, timestamp hlc.Timestamp, txnID *uuid.UUID, readTSCache bool,
) {
// This gives us a memory-efficient end key if end is empty.
if len(end) == 0 {
end = start.Next()
start = end[:len(start)]
}
tc.latest.Forward(timestamp)
// Only add to the cache if the timestamp is more recent than the
// low water mark.
if tc.lowWater.Less(timestamp) {
tcache := tc.wCache
if readTSCache {
tcache = tc.rCache
}
addRange := func(r interval.Range) {
value := cacheValue{timestamp: timestamp, txnID: txnID}
key := tcache.MakeKey(r.Start, r.End)
entry := makeCacheEntry(key, value)
tcache.AddEntry(entry)
}
r := interval.Range{
Start: interval.Comparable(start),
End: interval.Comparable(end),
}
// Check existing, overlapping entries and truncate/split/remove if
// superseded and in the past. If existing entries are in the future,
// subtract from the range/ranges that need to be added to cache.
for _, entry := range tcache.GetOverlaps(r.Start, r.End) {
cv := entry.Value.(*cacheValue)
key := entry.Key.(*cache.IntervalKey)
sCmp := r.Start.Compare(key.Start)
eCmp := r.End.Compare(key.End)
if cv.timestamp.Less(timestamp) {
// The existing interval has a timestamp less than the new
// interval. Compare interval ranges to determine how to
// modify existing interval.
switch {
case sCmp == 0 && eCmp == 0:
// New and old are equal; replace old with new and avoid the need to insert new.
//
// New: ------------
// Old: ------------
//
// New: ------------
// Old:
*cv = cacheValue{timestamp: timestamp, txnID: txnID}
tcache.MoveToEnd(entry)
return
case sCmp <= 0 && eCmp >= 0:
// New contains or is equal to old; delete old.
//
// New: ------------ ------------ ------------
// Old: -------- or ---------- or ----------
//
// New: ------------ ------------ ------------
// Old:
tcache.DelEntry(entry)
case sCmp > 0 && eCmp < 0:
// Old contains new; split up old into two.
//
// New: ----
// Old: ------------
//
// New: ----
// Old: ---- ----
oldEnd := key.End
key.End = r.Start
newKey := tcache.MakeKey(r.End, oldEnd)
newEntry := makeCacheEntry(newKey, *cv)
tcache.AddEntryAfter(newEntry, entry)
case eCmp >= 0:
// Left partial overlap; truncate old end.
//
// New: -------- --------
// Old: -------- or ------------
//
// New: -------- --------
// Old: ---- ----
key.End = r.Start
case sCmp <= 0:
// Right partial overlap; truncate old start.
//
// New: -------- --------
// Old: -------- or ------------
//
// New: -------- --------
// Old: ---- ----
key.Start = r.End
default:
panic(fmt.Sprintf("no overlap between %v and %v", key.Range, r))
}
} else if timestamp.Less(cv.timestamp) {
// The existing interval has a timestamp greater than the new interval.
// Compare interval ranges to determine how to modify new interval before
// adding it to the timestamp cache.
switch {
case sCmp >= 0 && eCmp <= 0:
// Old contains or is equal to new; no need to add.
//
// Old: ----------- ----------- ----------- -----------
// New: ----- or ----------- or -------- or --------
//
// Old: ----------- ----------- ----------- -----------
// New:
return
case sCmp < 0 && eCmp > 0:
// New contains old; split up old into two. We can add the left piece
// immediately because it is guaranteed to be before the rest of the
// overlaps.
//
// Old: ------
// New: ------------
//
// Old: ------
// New: --- ---
lr := interval.Range{Start: r.Start, End: key.Start}
addRange(lr)
r.Start = key.End
case eCmp > 0:
// Left partial overlap; truncate new start.
//
// Old: -------- --------
// New: -------- or ------------
//
// Old: -------- --------
// New: ---- ----
r.Start = key.End
case sCmp < 0:
// Right partial overlap; truncate new end.
//
// Old: -------- --------
// New: -------- or ------------
//
// Old: -------- --------
// New: ---- ----
r.End = key.Start
default:
panic(fmt.Sprintf("no overlap between %v and %v", key.Range, r))
}
} else if (cv.txnID == nil && txnID == nil) ||
(cv.txnID != nil && txnID != nil && *cv.txnID == *txnID) {
// The existing interval has a timestamp equal to the new
// interval, and the same transaction ID.
switch {
case sCmp >= 0 && eCmp <= 0:
// Old contains or is equal to new; no need to add.
//
// New: ----- or ----------- or -------- or --------
// Old: ----------- ----------- ----------- -----------
//
// New:
// Old: ----------- ----------- ----------- -----------
return
case sCmp <= 0 && eCmp >= 0:
// New contains old; delete old.
//
// New: ------------ ------------ ------------
// Old: -------- or ---------- or ----------
//
// New: ------------ ------------ ------------
// Old:
tcache.DelEntry(entry)
case eCmp >= 0:
// Left partial overlap; truncate old end.
//
// New: -------- --------
// Old: -------- or ------------
//
// New: -------- --------
// Old: ---- ----
key.End = r.Start
case sCmp <= 0:
// Right partial overlap; truncate old start.
//
// New: -------- --------
// Old: -------- or ------------
//
// New: -------- --------
// Old: ---- ----
key.Start = r.End
default:
panic(fmt.Sprintf("no overlap between %v and %v", key.Range, r))
}
} else {
// The existing interval has a timestamp equal to the new
// interval and a different transaction ID.
switch {
case sCmp == 0 && eCmp == 0:
// New and old are equal. Segment is no longer owned by any
// transaction.
//
// New: ------------
// Old: ------------
//
// New:
// Nil: ============
// Old:
cv.txnID = nil
return
case sCmp == 0 && eCmp > 0:
// New contains old, left-aligned. Clear ownership of the
// existing segment and truncate new.
//
// New: ------------
// Old: ----------
//
// New: --
// Nil: ==========
// Old:
cv.txnID = nil
r.Start = key.End
case sCmp < 0 && eCmp == 0:
// New contains old, right-aligned. Clear ownership of the
// existing segment and truncate new.
//
// New: ------------
// Old: ----------
//
// New: --
// Nil: ==========
// Old:
cv.txnID = nil
r.End = key.Start
case sCmp < 0 && eCmp > 0:
// New contains old; split into three segments with the
// overlap owned by no txn.
//
// New: ------------
// Old: --------
//
// New: -- --
// Nil: ========
// Old:
cv.txnID = nil
newKey := tcache.MakeKey(r.Start, key.Start)
newEntry := makeCacheEntry(newKey, cacheValue{timestamp: timestamp, txnID: txnID})
tcache.AddEntryAfter(newEntry, entry)
r.Start = key.End
case sCmp > 0 && eCmp < 0:
// Old contains new; split up old into two. New segment is
// owned by no txn.
//
// New: ----
// Old: ------------
//
// New:
// Nil: ====
// Old: ---- ----
txnID = nil
oldEnd := key.End
key.End = r.Start
newKey := tcache.MakeKey(r.End, oldEnd)
newEntry := makeCacheEntry(newKey, *cv)
tcache.AddEntryAfter(newEntry, entry)
case eCmp == 0:
// Old contains new, right-aligned; truncate old end and clear
// ownership of new segment.
//
// New: --------
// Old: ------------
//
// New:
// Nil: ========
// Old: ----
txnID = nil
key.End = r.Start
case sCmp == 0:
// Old contains new, left-aligned; truncate old start and
// clear ownership of new segment.
// New: --------
// Old: ------------
//
// New:
// Nil: ========
// Old: ----
txnID = nil
key.Start = r.End
case eCmp > 0:
// Left partial overlap; truncate old end and split new into
// segments owned by no txn (the overlap) and the new txn.
//
// New: --------
// Old: --------
//
// New: ----
// Nil: ====
// Old: ----
key.End, r.Start = r.Start, key.End
newKey := tcache.MakeKey(key.End, r.Start)
newCV := cacheValue{timestamp: cv.timestamp, txnID: nil}
newEntry := makeCacheEntry(newKey, newCV)
tcache.AddEntryAfter(newEntry, entry)
case sCmp < 0:
// Right partial overlap; truncate old start and split new into
// segments owned by no txn (the overlap) and the new txn.
//
// New: --------
// Old: --------
//
// New: ----
// Nil: ====
// Old: ----
key.Start, r.End = r.End, key.Start
newKey := tcache.MakeKey(r.End, key.Start)
newCV := cacheValue{timestamp: cv.timestamp, txnID: nil}
newEntry := makeCacheEntry(newKey, newCV)
tcache.AddEntryAfter(newEntry, entry)
default:
panic(fmt.Sprintf("no overlap between %v and %v", key.Range, r))
}
}
}
addRange(r)
}
}
