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[IMPROVED] Last msg lookup (KV Get) when subject is a literal subject #4232

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merged 1 commit into from Jun 10, 2023
Merged

[IMPROVED] Last msg lookup (KV Get) when subject is a literal subject #4232

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11 changes: 10 additions & 1 deletion server/filestore.go
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Expand Up @@ -4665,7 +4665,16 @@ func (fs *fileStore) loadLast(subj string, sm *StoreMsg) (lsm *StoreMsg, err err
mb.mu.Unlock()
return nil, err
}
_, _, l := mb.filteredPendingLocked(subj, wc, mb.first.seq)
var l uint64
// Optimize if subject is not a wildcard.
if !wc {
if ss := mb.fss[subj]; ss != nil {
l = ss.Last
}
}
if l == 0 {
_, _, l = mb.filteredPendingLocked(subj, wc, mb.first.seq)
}
if l > 0 {
if mb.cacheNotLoaded() {
if err := mb.loadMsgsWithLock(); err != nil {
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8 changes: 6 additions & 2 deletions server/memstore.go
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Expand Up @@ -864,6 +864,10 @@ func (ms *memStore) LoadLastMsg(subject string, smp *StoreMsg) (*StoreMsg, error

if subject == _EMPTY_ || subject == fwcs {
sm, ok = ms.msgs[ms.state.LastSeq]
} else if subjectIsLiteral(subject) {
if ss := ms.fss[subject]; ss != nil && ss.Msgs > 0 {
sm, ok = ms.msgs[ss.Last]
}
} else if ss := ms.filteredStateLocked(1, subject, true); ss.Msgs > 0 {
sm, ok = ms.msgs[ss.Last]
}
Expand Down Expand Up @@ -895,8 +899,8 @@ func (ms *memStore) LoadNextMsg(filter string, wc bool, start uint64, smp *Store

isAll := filter == _EMPTY_ || filter == fwcs

// Skip scan of mb.fss is number of messages in the block are less than
// 1/2 the number of subjects in mb.fss. Or we have a wc and lots of fss entries.
// Skip scan of ms.fss is number of messages in the block are less than
// 1/2 the number of subjects in ms.fss. Or we have a wc and lots of fss entries.
const linearScanMaxFSS = 256
doLinearScan := isAll || 2*int(ms.state.LastSeq-start) < len(ms.fss) || (wc && len(ms.fss) > linearScanMaxFSS)

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