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Save on slice allocations in histogramIterator (#9494)

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Signed-off-by: beorn7 <beorn@grafana.com>
This commit is contained in:
Björn Rabenstein 2021-10-13 11:13:49 +02:00 committed by GitHub
parent 468a89f1bf
commit 311673d62e
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 30 additions and 18 deletions
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48
tsdb/chunkenc/histogram.go
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@ -652,17 +652,10 @@ func (it *histogramIterator) Reset(b []byte) {
it.t, it.cnt, it.zCnt = 0, 0, 0
it.tDelta, it.cntDelta, it.zCntDelta = 0, 0, 0
// TODO(beorn7): Those will be recreated anyway.
// Either delete them here entirely or recycle them
// below if big enough.
for i := range it.pBuckets {
it.pBuckets[i] = 0
it.pBucketsDelta[i] = 0
}
for i := range it.nBuckets {
it.nBuckets[i] = 0
it.nBucketsDelta[i] = 0
}
it.pBuckets = it.pBuckets[:0]
it.pBucketsDelta = it.pBucketsDelta[:0]
it.nBuckets = it.nBuckets[:0]
it.pBucketsDelta = it.pBucketsDelta[:0]
it.sum = 0
it.leading = 0
@ -688,14 +681,33 @@ func (it *histogramIterator) Next() bool {
it.schema = schema
it.zThreshold = zeroThreshold
it.pSpans, it.nSpans = posSpans, negSpans
numPosBuckets, numNegBuckets := countSpans(posSpans), countSpans(negSpans)
if numPosBuckets > 0 {
it.pBuckets = make([]int64, numPosBuckets)
it.pBucketsDelta = make([]int64, numPosBuckets)
numPBuckets, numNBuckets := countSpans(posSpans), countSpans(negSpans)
// Allocate bucket slices as needed, recycling existing slices
// in case this iterator was reset and already has slices of a
// sufficient capacity..
if numPBuckets > 0 {
if cap(it.pBuckets) < numPBuckets {
it.pBuckets = make([]int64, numPBuckets)
// If cap(it.pBuckets) isn't sufficient, neither is cap(it.pBucketsDelta).
it.pBucketsDelta = make([]int64, numPBuckets)
} else {
for i := 0; i < numPBuckets; i++ {
it.pBuckets = append(it.pBuckets, 0)
it.pBucketsDelta = append(it.pBucketsDelta, 0)
}
}
}
if numNegBuckets > 0 {
it.nBuckets = make([]int64, numNegBuckets)
it.nBucketsDelta = make([]int64, numNegBuckets)
if numNBuckets > 0 {
if cap(it.nBuckets) < numNBuckets {
it.nBuckets = make([]int64, numNBuckets)
// If cap(it.nBuckets) isn't sufficient, neither is cap(it.nBucketsDelta).
it.nBucketsDelta = make([]int64, numNBuckets)
} else {
for i := 0; i < numNBuckets; i++ {
it.nBuckets = append(it.nBuckets, 0)
it.nBucketsDelta = append(it.nBucketsDelta, 0)
}
}
}
// Now read the actual data.