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[PERF] TSDB: Grow postings by doubling

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Go's built-in append() grows larger slices with factor 1.3, which means we do a lot more allocating and copying for larger postings.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2024-08-23 09:30:22 +01:00
parent 1435c8ae4a
commit 33adbe47b1
1 changed files with 10 additions and 1 deletions
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11
tsdb/index/postings.go
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@ -345,13 +345,22 @@ func (p *MemPostings) Add(id storage.SeriesRef, lset labels.Labels) {
p.mtx.Unlock()
}
func appendWithExponentialGrowth[T any](a []T, v T) []T {
if cap(a) < len(a)+1 {
newList := make([]T, len(a), len(a)*2+1)
copy(newList, a)
a = newList
}
return append(a, v)
}
func (p *MemPostings) addFor(id storage.SeriesRef, l labels.Label) {
nm, ok := p.m[l.Name]
if !ok {
nm = map[string][]storage.SeriesRef{}
p.m[l.Name] = nm
}
list := append(nm[l.Value], id)
list := appendWithExponentialGrowth(nm[l.Value], id)
nm[l.Value] = list
if !p.ordered {