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TSDB: Pre-size buffer to read samples from WAL

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When reading the WAL this method is called with buffers from a pool, on
multiple goroutines. Pre-allocating sufficient size avoids slow growth
and many reallocations in `append`.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2023-10-17 17:31:21 +00:00
parent a06c6680aa
commit 26fa2e8356
1 changed files with 4 additions and 0 deletions
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4
tsdb/record/record.go
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@ -304,6 +304,10 @@ func (d *Decoder) Samples(rec []byte, samples []RefSample) ([]RefSample, error)
baseRef = dec.Be64()
baseTime = dec.Be64int64()
)
// Allow 1 byte for each varint and 8 for the value; the output slice must be at least that big.
if minSize := dec.Len() / (1 + 1 + 8); cap(samples) < minSize {
samples = make([]RefSample, 0, minSize)
}
for len(dec.B) > 0 && dec.Err() == nil {
dref := dec.Varint64()
dtime := dec.Varint64()