prometheus/tsdb/index/postingsstats.go

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// Copyright 2019 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package index
import (
"math"
"golang.org/x/exp/slices"
)
// Stat holds values for a single cardinality statistic.
type Stat struct {
Name string
Count uint64
}
type maxHeap struct {
maxLength int
minValue uint64
minIndex int
Items []Stat
}
func (m *maxHeap) init(length int) {
m.maxLength = length
m.minValue = math.MaxUint64
m.Items = make([]Stat, 0, length)
}
func (m *maxHeap) push(item Stat) {
if len(m.Items) < m.maxLength {
if item.Count < m.minValue {
m.minValue = item.Count
m.minIndex = len(m.Items)
}
m.Items = append(m.Items, item)
return
}
if item.Count < m.minValue {
return
}
m.Items[m.minIndex] = item
m.minValue = item.Count
for i, stat := range m.Items {
if stat.Count < m.minValue {
m.minValue = stat.Count
m.minIndex = i
}
}
}
func (m *maxHeap) get() []Stat {
slices.SortFunc(m.Items, func(a, b Stat) int {
switch {
case b.Count < a.Count:
return -1
case b.Count > a.Count:
return 1
default:
return 0
}
})
return m.Items
}