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Labels: reduce allocations when creating from TSDB WAL (#13044)

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* Labels: reduce allocations when creating from TSDB

When reading the WAL, by passing references into the buffer we can avoid
copying strings under `-tags stringlabels`.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
This commit is contained in:
Bryan Boreham 2023-11-14 11:36:35 +00:00 committed by GitHub
parent b718dca70b
commit 1bfb3ed062
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 16 additions and 4 deletions
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7
model/labels/labels.go
View File

@ -617,6 +617,13 @@ func (b *ScratchBuilder) Add(name, value string) {
b.add = append(b.add, Label{Name: name, Value: value})
}
// Add a name/value pair, using []byte instead of string.
// The '-tags stringlabels' version of this function is unsafe, hence the name.
// This version is safe - it copies the strings immediately - but we keep the same name so everything compiles.
func (b *ScratchBuilder) UnsafeAddBytes(name, value []byte) {
b.add = append(b.add, Label{Name: string(name), Value: string(value)})
}
// Sort the labels added so far by name.
func (b *ScratchBuilder) Sort() {
slices.SortFunc(b.add, func(a, b Label) int { return strings.Compare(a.Name, b.Name) })

6
model/labels/labels_stringlabels.go
View File

@ -829,6 +829,12 @@ func (b *ScratchBuilder) Add(name, value string) {
b.add = append(b.add, Label{Name: name, Value: value})
}
// Add a name/value pair, using []byte instead of string to reduce memory allocations.
// The values must remain live until Labels() is called.
func (b *ScratchBuilder) UnsafeAddBytes(name, value []byte) {
b.add = append(b.add, Label{Name: yoloString(name), Value: yoloString(value)})
}
// Sort the labels added so far by name.
func (b *ScratchBuilder) Sort() {
slices.SortFunc(b.add, func(a, b Label) int { return strings.Compare(a.Name, b.Name) })

7
tsdb/record/record.go
View File

@ -279,13 +279,12 @@ func (d *Decoder) Metadata(rec []byte, metadata []RefMetadata) ([]RefMetadata, e
// DecodeLabels decodes one set of labels from buf.
func (d *Decoder) DecodeLabels(dec *encoding.Decbuf) labels.Labels {
// TODO: reconsider if this function could be pushed down into labels.Labels to be more efficient.
d.builder.Reset()
nLabels := dec.Uvarint()
for i := 0; i < nLabels; i++ {
lName := dec.UvarintStr()
lValue := dec.UvarintStr()
d.builder.Add(lName, lValue)
lName := dec.UvarintBytes()
lValue := dec.UvarintBytes()
d.builder.UnsafeAddBytes(lName, lValue)
}
return d.builder.Labels()
}