prometheus/postings.go

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// Copyright 2017 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.
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package tsdb
import (
"encoding/binary"
"sort"
"strings"
)
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type memPostings struct {
m map[term][]uint32
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}
type term struct {
name, value string
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}
// Postings returns an iterator over the postings list for s.
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func (p *memPostings) get(t term) Postings {
l := p.m[t]
if l == nil {
return emptyPostings
}
return newListPostings(l)
}
// add adds a document to the index. The caller has to ensure that no
// term argument appears twice.
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func (p *memPostings) add(id uint32, terms ...term) {
for _, t := range terms {
p.m[t] = append(p.m[t], id)
}
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}
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// Postings provides iterative access over a postings list.
type Postings interface {
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// Next advances the iterator and returns true if another value was found.
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Next() bool
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// Seek advances the iterator to value v or greater and returns
// true if a value was found.
Seek(v uint32) bool
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// At returns the value at the current iterator position.
At() uint32
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// Err returns the last error of the iterator.
Err() error
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}
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// errPostings is an empty iterator that always errors.
type errPostings struct {
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err error
}
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func (e errPostings) Next() bool { return false }
func (e errPostings) Seek(uint32) bool { return false }
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func (e errPostings) At() uint32 { return 0 }
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func (e errPostings) Err() error { return e.err }
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var emptyPostings = errPostings{}
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// Intersect returns a new postings list over the intersection of the
// input postings.
func Intersect(its ...Postings) Postings {
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if len(its) == 0 {
return emptyPostings
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}
a := its[0]
for _, b := range its[1:] {
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a = newIntersectPostings(a, b)
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}
return a
}
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type intersectPostings struct {
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a, b Postings
aok, bok bool
cur uint32
}
func newIntersectPostings(a, b Postings) *intersectPostings {
return &intersectPostings{a: a, b: b}
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}
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func (it *intersectPostings) At() uint32 {
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return it.cur
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}
func (it *intersectPostings) doNext(id uint32) bool {
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for {
if !it.b.Seek(id) {
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return false
}
if vb := it.b.At(); vb != id {
if !it.a.Seek(vb) {
return false
}
id = it.a.At()
if vb != id {
continue
}
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}
it.cur = id
return true
}
}
func (it *intersectPostings) Next() bool {
if !it.a.Next() {
return false
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}
return it.doNext(it.a.At())
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}
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func (it *intersectPostings) Seek(id uint32) bool {
if !it.a.Seek(id) {
return false
}
return it.doNext(it.a.At())
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}
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func (it *intersectPostings) Err() error {
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if it.a.Err() != nil {
return it.a.Err()
}
return it.b.Err()
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}
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// Merge returns a new iterator over the union of the input iterators.
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func Merge(its ...Postings) Postings {
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if len(its) == 0 {
return nil
}
a := its[0]
for _, b := range its[1:] {
a = newMergedPostings(a, b)
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}
return a
}
type mergedPostings struct {
a, b Postings
initialized bool
aok, bok bool
cur uint32
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}
func newMergedPostings(a, b Postings) *mergedPostings {
return &mergedPostings{a: a, b: b}
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}
func (it *mergedPostings) At() uint32 {
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return it.cur
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}
func (it *mergedPostings) Next() bool {
if !it.initialized {
it.aok = it.a.Next()
it.bok = it.b.Next()
it.initialized = true
}
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if !it.aok && !it.bok {
return false
}
if !it.aok {
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it.cur = it.b.At()
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it.bok = it.b.Next()
return true
}
if !it.bok {
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it.cur = it.a.At()
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it.aok = it.a.Next()
return true
}
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acur, bcur := it.a.At(), it.b.At()
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if acur < bcur {
it.cur = acur
it.aok = it.a.Next()
} else if acur > bcur {
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it.cur = bcur
it.bok = it.b.Next()
} else {
it.cur = acur
it.aok = it.a.Next()
it.bok = it.b.Next()
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}
return true
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}
func (it *mergedPostings) Seek(id uint32) bool {
if it.cur >= id {
return true
}
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it.aok = it.a.Seek(id)
it.bok = it.b.Seek(id)
it.initialized = true
return it.Next()
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}
func (it *mergedPostings) Err() error {
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if it.a.Err() != nil {
return it.a.Err()
}
return it.b.Err()
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}
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// listPostings implements the Postings interface over a plain list.
type listPostings struct {
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list []uint32
cur uint32
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}
func newListPostings(list []uint32) *listPostings {
return &listPostings{list: list}
}
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func (it *listPostings) At() uint32 {
return it.cur
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}
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func (it *listPostings) Next() bool {
if len(it.list) > 0 {
it.cur = it.list[0]
it.list = it.list[1:]
return true
}
it.cur = 0
return false
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}
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func (it *listPostings) Seek(x uint32) bool {
// If the current value satisfies, then return.
if it.cur >= x {
return true
}
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// Do binary search between current position and end.
i := sort.Search(len(it.list), func(i int) bool {
return it.list[i] >= x
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})
if i < len(it.list) {
it.cur = it.list[i]
it.list = it.list[i+1:]
return true
}
it.list = nil
return false
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}
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func (it *listPostings) Err() error {
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return nil
}
// bigEndianPostings implements the Postings interface over a byte stream of
// big endian numbers.
type bigEndianPostings struct {
list []byte
cur uint32
}
func newBigEndianPostings(list []byte) *bigEndianPostings {
return &bigEndianPostings{list: list}
}
func (it *bigEndianPostings) At() uint32 {
return it.cur
}
func (it *bigEndianPostings) Next() bool {
if len(it.list) >= 4 {
it.cur = binary.BigEndian.Uint32(it.list)
it.list = it.list[4:]
return true
}
return false
}
func (it *bigEndianPostings) Seek(x uint32) bool {
if it.cur >= x {
return true
}
num := len(it.list) / 4
// Do binary search between current position and end.
i := sort.Search(num, func(i int) bool {
return binary.BigEndian.Uint32(it.list[i*4:]) >= x
})
if i < num {
j := i * 4
it.cur = binary.BigEndian.Uint32(it.list[j:])
it.list = it.list[j+4:]
return true
}
it.list = nil
return false
}
func (it *bigEndianPostings) Err() error {
return nil
}
type stringset map[string]struct{}
func (ss stringset) set(s string) {
ss[s] = struct{}{}
}
func (ss stringset) has(s string) bool {
_, ok := ss[s]
return ok
}
func (ss stringset) String() string {
return strings.Join(ss.slice(), ",")
}
func (ss stringset) slice() []string {
slice := make([]string, 0, len(ss))
for k := range ss {
slice = append(slice, k)
}
sort.Strings(slice)
return slice
}