web/api/v1/api.go
func mergeLabels(primary, secondary []prompb.Label) []prompb.Label {
	result := make([]prompb.Label, 0, len(primary)+len(secondary))
	i, j := 0, 0
	for i < len(primary) && j < len(secondary) {
		if primary[i].Name < secondary[j].Name {
			result = append(result, primary[i])
			i++
		} else if primary[i].Name > secondary[j].Name {
			result = append(result, secondary[j])
			j++
		} else {
			result = append(result, primary[i])
			i++
			j++
		}
	}
	for ; i < len(primary); i++ {
		result = append(result, primary[i])
	}
	for ; j < len(secondary); j++ {
		result = append(result, secondary[j])
	}
	return result
}
func mergeLabels(primary, secondary []prompb.Label) []prompb.Label {
	result := make([]prompb.Label, 0, len(primary)+len(secondary))
	i, j := 0, 0
	for i < len(primary) && j < len(secondary) {
		if primary[i].Name < secondary[j].Name {
			result = append(result, primary[i])
			i++
		} else if primary[i].Name > secondary[j].Name {
			result = append(result, secondary[j])
			j++
		} else {
			result = append(result, primary[i])
			i++
			j++
		}
	}
	for ; i < len(primary); i++ {
		result = append(result, primary[i])
	}
	for ; j < len(secondary); j++ {
		result = append(result, secondary[j])
	}
	return result
}
// mergeLabels merges two sets of sorted proto labels, preferring those in
// primary to those in secondary when there is an overlap.