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Improve performance of WithLabelValues(...) #1360

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merged 1 commit into from Oct 5, 2023
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Improve performance of WithLabelValues(...) #1360

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2 changes: 2 additions & 0 deletions prometheus/labels.go
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Expand Up @@ -165,6 +165,8 @@ func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {

func validateLabelValues(vals []string, expectedNumberOfValues int) error {
if len(vals) != expectedNumberOfValues {
// The call below makes vals escape, copy them to avoid that.
vals := append([]string(nil), vals...)
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		vals := vals

Would this have the same effect?

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Interesting, I don't know. Try it!

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I don't think it would work, as the slice still references the array that we've allocated on stack.

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Note that we already receive a copy of vals when this function is called, so this doesn't change anything.

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good point, thanks again!

return fmt.Errorf(
"%w: expected %d label values but got %d in %#v",
errInconsistentCardinality, expectedNumberOfValues,
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