prometheus/tsdb/index/postings_test.go
Dieter Plaetinck cda025b5b5
TSDB: demistify SeriesRefs and ChunkRefs (#9536)
* TSDB: demistify seriesRefs and ChunkRefs

The TSDB package contains many types of series and chunk references,
all shrouded in uint types.  Often the same uint value may
actually mean one of different types, in non-obvious ways.

This PR aims to clarify the code and help navigating to relevant docs,
usage, etc much quicker.

Concretely:

* Use appropriately named types and document their semantics and
  relations.
* Make multiplexing and demuxing of types explicit
  (on the boundaries between concrete implementations and generic
  interfaces).
* Casting between different types should be free.  None of the changes
  should have any impact on how the code runs.

TODO: Implement BlockSeriesRef where appropriate (for a future PR)

Signed-off-by: Dieter Plaetinck <dieter@grafana.com>

* feedback

Signed-off-by: Dieter Plaetinck <dieter@grafana.com>

* agent: demistify seriesRefs and ChunkRefs

Signed-off-by: Dieter Plaetinck <dieter@grafana.com>
2021-11-06 15:40:04 +05:30

932 lines
20 KiB
Go

// 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.
package index
import (
"encoding/binary"
"fmt"
"math/rand"
"sort"
"strconv"
"testing"
"github.com/stretchr/testify/require"
"github.com/prometheus/prometheus/pkg/labels"
"github.com/prometheus/prometheus/storage"
)
func TestMemPostings_addFor(t *testing.T) {
p := NewMemPostings()
p.m[allPostingsKey.Name] = map[string][]storage.SeriesRef{}
p.m[allPostingsKey.Name][allPostingsKey.Value] = []storage.SeriesRef{1, 2, 3, 4, 6, 7, 8}
p.addFor(5, allPostingsKey)
require.Equal(t, []storage.SeriesRef{1, 2, 3, 4, 5, 6, 7, 8}, p.m[allPostingsKey.Name][allPostingsKey.Value])
}
func TestMemPostings_ensureOrder(t *testing.T) {
p := NewUnorderedMemPostings()
p.m["a"] = map[string][]storage.SeriesRef{}
for i := 0; i < 100; i++ {
l := make([]storage.SeriesRef, 100)
for j := range l {
l[j] = storage.SeriesRef(rand.Uint64())
}
v := fmt.Sprintf("%d", i)
p.m["a"][v] = l
}
p.EnsureOrder()
for _, e := range p.m {
for _, l := range e {
ok := sort.SliceIsSorted(l, func(i, j int) bool {
return l[i] < l[j]
})
if !ok {
t.Fatalf("postings list %v is not sorted", l)
}
}
}
}
func BenchmarkMemPostings_ensureOrder(b *testing.B) {
tests := map[string]struct {
numLabels int
numValuesPerLabel int
numRefsPerValue int
}{
"many values per label": {
numLabels: 100,
numValuesPerLabel: 10000,
numRefsPerValue: 100,
},
"few values per label": {
numLabels: 1000000,
numValuesPerLabel: 1,
numRefsPerValue: 100,
},
"few refs per label value": {
numLabels: 1000,
numValuesPerLabel: 1000,
numRefsPerValue: 10,
},
}
for testName, testData := range tests {
b.Run(testName, func(b *testing.B) {
p := NewUnorderedMemPostings()
// Generate postings.
for l := 0; l < testData.numLabels; l++ {
labelName := strconv.Itoa(l)
p.m[labelName] = map[string][]storage.SeriesRef{}
for v := 0; v < testData.numValuesPerLabel; v++ {
refs := make([]storage.SeriesRef, testData.numRefsPerValue)
for j := range refs {
refs[j] = storage.SeriesRef(rand.Uint64())
}
labelValue := strconv.Itoa(v)
p.m[labelName][labelValue] = refs
}
}
b.ResetTimer()
for n := 0; n < b.N; n++ {
p.EnsureOrder()
p.ordered = false
}
})
}
}
func TestIntersect(t *testing.T) {
a := newListPostings(1, 2, 3)
b := newListPostings(2, 3, 4)
cases := []struct {
in []Postings
res Postings
}{
{
in: []Postings{},
res: EmptyPostings(),
},
{
in: []Postings{a, b, EmptyPostings()},
res: EmptyPostings(),
},
{
in: []Postings{b, a, EmptyPostings()},
res: EmptyPostings(),
},
{
in: []Postings{EmptyPostings(), b, a},
res: EmptyPostings(),
},
{
in: []Postings{EmptyPostings(), a, b},
res: EmptyPostings(),
},
{
in: []Postings{a, EmptyPostings(), b},
res: EmptyPostings(),
},
{
in: []Postings{b, EmptyPostings(), a},
res: EmptyPostings(),
},
{
in: []Postings{b, EmptyPostings(), a, a, b, a, a, a},
res: EmptyPostings(),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 5),
newListPostings(6, 7, 8, 9, 10),
},
res: newListPostings(),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 5),
newListPostings(4, 5, 6, 7, 8),
},
res: newListPostings(4, 5),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 9, 10),
newListPostings(1, 4, 5, 6, 7, 8, 10, 11),
},
res: newListPostings(1, 4, 10),
},
{
in: []Postings{
newListPostings(1),
newListPostings(0, 1),
},
res: newListPostings(1),
},
{
in: []Postings{
newListPostings(1),
},
res: newListPostings(1),
},
{
in: []Postings{
newListPostings(1),
newListPostings(),
},
res: newListPostings(),
},
{
in: []Postings{
newListPostings(),
newListPostings(),
},
res: newListPostings(),
},
}
for _, c := range cases {
t.Run("", func(t *testing.T) {
if c.res == nil {
t.Fatal("intersect result expectancy cannot be nil")
}
expected, err := ExpandPostings(c.res)
require.NoError(t, err)
i := Intersect(c.in...)
if c.res == EmptyPostings() {
require.Equal(t, EmptyPostings(), i)
return
}
if i == EmptyPostings() {
t.Fatal("intersect unexpected result: EmptyPostings sentinel")
}
res, err := ExpandPostings(i)
require.NoError(t, err)
require.Equal(t, expected, res)
})
}
}
func TestMultiIntersect(t *testing.T) {
cases := []struct {
p [][]storage.SeriesRef
res []storage.SeriesRef
}{
{
p: [][]storage.SeriesRef{
{1, 2, 3, 4, 5, 6, 1000, 1001},
{2, 4, 5, 6, 7, 8, 999, 1001},
{1, 2, 5, 6, 7, 8, 1001, 1200},
},
res: []storage.SeriesRef{2, 5, 6, 1001},
},
// One of the reproducible cases for:
// https://github.com/prometheus/prometheus/issues/2616
// The initialisation of intersectPostings was moving the iterator forward
// prematurely making us miss some postings.
{
p: [][]storage.SeriesRef{
{1, 2},
{1, 2},
{1, 2},
{2},
},
res: []storage.SeriesRef{2},
},
}
for _, c := range cases {
ps := make([]Postings, 0, len(c.p))
for _, postings := range c.p {
ps = append(ps, newListPostings(postings...))
}
res, err := ExpandPostings(Intersect(ps...))
require.NoError(t, err)
require.Equal(t, c.res, res)
}
}
func BenchmarkIntersect(t *testing.B) {
t.Run("LongPostings1", func(bench *testing.B) {
var a, b, c, d []storage.SeriesRef
for i := 0; i < 10000000; i += 2 {
a = append(a, storage.SeriesRef(i))
}
for i := 5000000; i < 5000100; i += 4 {
b = append(b, storage.SeriesRef(i))
}
for i := 5090000; i < 5090600; i += 4 {
b = append(b, storage.SeriesRef(i))
}
for i := 4990000; i < 5100000; i++ {
c = append(c, storage.SeriesRef(i))
}
for i := 4000000; i < 6000000; i++ {
d = append(d, storage.SeriesRef(i))
}
i1 := newListPostings(a...)
i2 := newListPostings(b...)
i3 := newListPostings(c...)
i4 := newListPostings(d...)
bench.ResetTimer()
bench.ReportAllocs()
for i := 0; i < bench.N; i++ {
if _, err := ExpandPostings(Intersect(i1, i2, i3, i4)); err != nil {
bench.Fatal(err)
}
}
})
t.Run("LongPostings2", func(bench *testing.B) {
var a, b, c, d []storage.SeriesRef
for i := 0; i < 12500000; i++ {
a = append(a, storage.SeriesRef(i))
}
for i := 7500000; i < 12500000; i++ {
b = append(b, storage.SeriesRef(i))
}
for i := 9000000; i < 20000000; i++ {
c = append(c, storage.SeriesRef(i))
}
for i := 10000000; i < 12000000; i++ {
d = append(d, storage.SeriesRef(i))
}
i1 := newListPostings(a...)
i2 := newListPostings(b...)
i3 := newListPostings(c...)
i4 := newListPostings(d...)
bench.ResetTimer()
bench.ReportAllocs()
for i := 0; i < bench.N; i++ {
if _, err := ExpandPostings(Intersect(i1, i2, i3, i4)); err != nil {
bench.Fatal(err)
}
}
})
// Many matchers(k >> n).
t.Run("ManyPostings", func(bench *testing.B) {
var its []Postings
// 100000 matchers(k=100000).
for i := 0; i < 100000; i++ {
var temp []storage.SeriesRef
for j := storage.SeriesRef(1); j < 100; j++ {
temp = append(temp, j)
}
its = append(its, newListPostings(temp...))
}
bench.ResetTimer()
bench.ReportAllocs()
for i := 0; i < bench.N; i++ {
if _, err := ExpandPostings(Intersect(its...)); err != nil {
bench.Fatal(err)
}
}
})
}
func TestMultiMerge(t *testing.T) {
i1 := newListPostings(1, 2, 3, 4, 5, 6, 1000, 1001)
i2 := newListPostings(2, 4, 5, 6, 7, 8, 999, 1001)
i3 := newListPostings(1, 2, 5, 6, 7, 8, 1001, 1200)
res, err := ExpandPostings(Merge(i1, i2, i3))
require.NoError(t, err)
require.Equal(t, []storage.SeriesRef{1, 2, 3, 4, 5, 6, 7, 8, 999, 1000, 1001, 1200}, res)
}
func TestMergedPostings(t *testing.T) {
cases := []struct {
in []Postings
res Postings
}{
{
in: []Postings{},
res: EmptyPostings(),
},
{
in: []Postings{
newListPostings(),
newListPostings(),
},
res: EmptyPostings(),
},
{
in: []Postings{
newListPostings(),
},
res: newListPostings(),
},
{
in: []Postings{
EmptyPostings(),
EmptyPostings(),
EmptyPostings(),
EmptyPostings(),
},
res: EmptyPostings(),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 5),
newListPostings(6, 7, 8, 9, 10),
},
res: newListPostings(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 5),
newListPostings(4, 5, 6, 7, 8),
},
res: newListPostings(1, 2, 3, 4, 5, 6, 7, 8),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 9, 10),
newListPostings(1, 4, 5, 6, 7, 8, 10, 11),
},
res: newListPostings(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11),
},
{
in: []Postings{
newListPostings(1, 2, 3, 4, 9, 10),
EmptyPostings(),
newListPostings(1, 4, 5, 6, 7, 8, 10, 11),
},
res: newListPostings(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11),
},
{
in: []Postings{
newListPostings(1, 2),
newListPostings(),
},
res: newListPostings(1, 2),
},
{
in: []Postings{
newListPostings(1, 2),
EmptyPostings(),
},
res: newListPostings(1, 2),
},
}
for _, c := range cases {
t.Run("", func(t *testing.T) {
if c.res == nil {
t.Fatal("merge result expectancy cannot be nil")
}
expected, err := ExpandPostings(c.res)
require.NoError(t, err)
m := Merge(c.in...)
if c.res == EmptyPostings() {
require.Equal(t, EmptyPostings(), m)
return
}
if m == EmptyPostings() {
t.Fatal("merge unexpected result: EmptyPostings sentinel")
}
res, err := ExpandPostings(m)
require.NoError(t, err)
require.Equal(t, expected, res)
})
}
}
func TestMergedPostingsSeek(t *testing.T) {
cases := []struct {
a, b []storage.SeriesRef
seek storage.SeriesRef
success bool
res []storage.SeriesRef
}{
{
a: []storage.SeriesRef{2, 3, 4, 5},
b: []storage.SeriesRef{6, 7, 8, 9, 10},
seek: 1,
success: true,
res: []storage.SeriesRef{2, 3, 4, 5, 6, 7, 8, 9, 10},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 5},
b: []storage.SeriesRef{6, 7, 8, 9, 10},
seek: 2,
success: true,
res: []storage.SeriesRef{2, 3, 4, 5, 6, 7, 8, 9, 10},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 5},
b: []storage.SeriesRef{4, 5, 6, 7, 8},
seek: 9,
success: false,
res: nil,
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 4, 5, 6, 7, 8, 10, 11},
seek: 10,
success: true,
res: []storage.SeriesRef{10, 11},
},
}
for _, c := range cases {
a := newListPostings(c.a...)
b := newListPostings(c.b...)
p := Merge(a, b)
require.Equal(t, c.success, p.Seek(c.seek))
// After Seek(), At() should be called.
if c.success {
start := p.At()
lst, err := ExpandPostings(p)
require.NoError(t, err)
lst = append([]storage.SeriesRef{start}, lst...)
require.Equal(t, c.res, lst)
}
}
}
func TestRemovedPostings(t *testing.T) {
cases := []struct {
a, b []storage.SeriesRef
res []storage.SeriesRef
}{
{
a: nil,
b: nil,
res: []storage.SeriesRef(nil),
},
{
a: []storage.SeriesRef{1, 2, 3, 4},
b: nil,
res: []storage.SeriesRef{1, 2, 3, 4},
},
{
a: nil,
b: []storage.SeriesRef{1, 2, 3, 4},
res: []storage.SeriesRef(nil),
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 5},
b: []storage.SeriesRef{6, 7, 8, 9, 10},
res: []storage.SeriesRef{1, 2, 3, 4, 5},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 5},
b: []storage.SeriesRef{4, 5, 6, 7, 8},
res: []storage.SeriesRef{1, 2, 3},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 4, 5, 6, 7, 8, 10, 11},
res: []storage.SeriesRef{2, 3, 9},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11},
res: []storage.SeriesRef(nil),
},
}
for _, c := range cases {
a := newListPostings(c.a...)
b := newListPostings(c.b...)
res, err := ExpandPostings(newRemovedPostings(a, b))
require.NoError(t, err)
require.Equal(t, c.res, res)
}
}
func TestRemovedNextStackoverflow(t *testing.T) {
var full []storage.SeriesRef
var remove []storage.SeriesRef
var i storage.SeriesRef
for i = 0; i < 1e7; i++ {
full = append(full, i)
remove = append(remove, i)
}
flp := newListPostings(full...)
rlp := newListPostings(remove...)
rp := newRemovedPostings(flp, rlp)
gotElem := false
for rp.Next() {
gotElem = true
}
require.NoError(t, rp.Err())
require.False(t, gotElem)
}
func TestRemovedPostingsSeek(t *testing.T) {
cases := []struct {
a, b []storage.SeriesRef
seek storage.SeriesRef
success bool
res []storage.SeriesRef
}{
{
a: []storage.SeriesRef{2, 3, 4, 5},
b: []storage.SeriesRef{6, 7, 8, 9, 10},
seek: 1,
success: true,
res: []storage.SeriesRef{2, 3, 4, 5},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 5},
b: []storage.SeriesRef{6, 7, 8, 9, 10},
seek: 2,
success: true,
res: []storage.SeriesRef{2, 3, 4, 5},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 5},
b: []storage.SeriesRef{4, 5, 6, 7, 8},
seek: 9,
success: false,
res: nil,
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 4, 5, 6, 7, 8, 10, 11},
seek: 10,
success: false,
res: nil,
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 4, 5, 6, 7, 8, 11},
seek: 4,
success: true,
res: []storage.SeriesRef{9, 10},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 4, 5, 6, 7, 8, 11},
seek: 5,
success: true,
res: []storage.SeriesRef{9, 10},
},
{
a: []storage.SeriesRef{1, 2, 3, 4, 9, 10},
b: []storage.SeriesRef{1, 4, 5, 6, 7, 8, 11},
seek: 10,
success: true,
res: []storage.SeriesRef{10},
},
}
for _, c := range cases {
a := newListPostings(c.a...)
b := newListPostings(c.b...)
p := newRemovedPostings(a, b)
require.Equal(t, c.success, p.Seek(c.seek))
// After Seek(), At() should be called.
if c.success {
start := p.At()
lst, err := ExpandPostings(p)
require.NoError(t, err)
lst = append([]storage.SeriesRef{start}, lst...)
require.Equal(t, c.res, lst)
}
}
}
func TestBigEndian(t *testing.T) {
num := 1000
// mock a list as postings
ls := make([]uint32, num)
ls[0] = 2
for i := 1; i < num; i++ {
ls[i] = ls[i-1] + uint32(rand.Int31n(25)) + 2
}
beLst := make([]byte, num*4)
for i := 0; i < num; i++ {
b := beLst[i*4 : i*4+4]
binary.BigEndian.PutUint32(b, ls[i])
}
t.Run("Iteration", func(t *testing.T) {
bep := newBigEndianPostings(beLst)
for i := 0; i < num; i++ {
require.True(t, bep.Next())
require.Equal(t, storage.SeriesRef(ls[i]), bep.At())
}
require.False(t, bep.Next())
require.NoError(t, bep.Err())
})
t.Run("Seek", func(t *testing.T) {
table := []struct {
seek uint32
val uint32
found bool
}{
{
ls[0] - 1, ls[0], true,
},
{
ls[4], ls[4], true,
},
{
ls[500] - 1, ls[500], true,
},
{
ls[600] + 1, ls[601], true,
},
{
ls[600] + 1, ls[601], true,
},
{
ls[600] + 1, ls[601], true,
},
{
ls[0], ls[601], true,
},
{
ls[600], ls[601], true,
},
{
ls[999], ls[999], true,
},
{
ls[999] + 10, ls[999], false,
},
}
bep := newBigEndianPostings(beLst)
for _, v := range table {
require.Equal(t, v.found, bep.Seek(storage.SeriesRef(v.seek)))
require.Equal(t, storage.SeriesRef(v.val), bep.At())
require.NoError(t, bep.Err())
}
})
}
func TestIntersectWithMerge(t *testing.T) {
// One of the reproducible cases for:
// https://github.com/prometheus/prometheus/issues/2616
a := newListPostings(21, 22, 23, 24, 25, 30)
b := Merge(
newListPostings(10, 20, 30),
newListPostings(15, 26, 30),
)
p := Intersect(a, b)
res, err := ExpandPostings(p)
require.NoError(t, err)
require.Equal(t, []storage.SeriesRef{30}, res)
}
func TestWithoutPostings(t *testing.T) {
cases := []struct {
base Postings
drop Postings
res Postings
}{
{
base: EmptyPostings(),
drop: EmptyPostings(),
res: EmptyPostings(),
},
{
base: EmptyPostings(),
drop: newListPostings(1, 2),
res: EmptyPostings(),
},
{
base: newListPostings(1, 2),
drop: EmptyPostings(),
res: newListPostings(1, 2),
},
{
base: newListPostings(),
drop: newListPostings(),
res: newListPostings(),
},
{
base: newListPostings(1, 2, 3),
drop: newListPostings(),
res: newListPostings(1, 2, 3),
},
{
base: newListPostings(1, 2, 3),
drop: newListPostings(4, 5, 6),
res: newListPostings(1, 2, 3),
},
{
base: newListPostings(1, 2, 3),
drop: newListPostings(3, 4, 5),
res: newListPostings(1, 2),
},
}
for _, c := range cases {
t.Run("", func(t *testing.T) {
if c.res == nil {
t.Fatal("without result expectancy cannot be nil")
}
expected, err := ExpandPostings(c.res)
require.NoError(t, err)
w := Without(c.base, c.drop)
if c.res == EmptyPostings() {
require.Equal(t, EmptyPostings(), w)
return
}
if w == EmptyPostings() {
t.Fatal("without unexpected result: EmptyPostings sentinel")
}
res, err := ExpandPostings(w)
require.NoError(t, err)
require.Equal(t, expected, res)
})
}
}
func BenchmarkPostings_Stats(b *testing.B) {
p := NewMemPostings()
var seriesID storage.SeriesRef
createPostingsLabelValues := func(name, valuePrefix string, count int) {
for n := 1; n < count; n++ {
value := fmt.Sprintf("%s-%d", valuePrefix, n)
p.Add(seriesID, labels.FromStrings(name, value))
seriesID++
}
}
createPostingsLabelValues("__name__", "metrics_name_can_be_very_big_and_bad", 1e3)
for i := 0; i < 20; i++ {
createPostingsLabelValues(fmt.Sprintf("host-%d", i), "metrics_name_can_be_very_big_and_bad", 1e3)
createPostingsLabelValues(fmt.Sprintf("instance-%d", i), "10.0.IP.", 1e3)
createPostingsLabelValues(fmt.Sprintf("job-%d", i), "Small_Job_name", 1e3)
createPostingsLabelValues(fmt.Sprintf("err-%d", i), "avg_namespace-", 1e3)
createPostingsLabelValues(fmt.Sprintf("team-%d", i), "team-", 1e3)
createPostingsLabelValues(fmt.Sprintf("container_name-%d", i), "pod-", 1e3)
createPostingsLabelValues(fmt.Sprintf("cluster-%d", i), "newcluster-", 1e3)
createPostingsLabelValues(fmt.Sprintf("uid-%d", i), "123412312312312311-", 1e3)
createPostingsLabelValues(fmt.Sprintf("area-%d", i), "new_area_of_work-", 1e3)
createPostingsLabelValues(fmt.Sprintf("request_id-%d", i), "owner_name_work-", 1e3)
}
b.ResetTimer()
for n := 0; n < b.N; n++ {
p.Stats("__name__")
}
}
func TestMemPostings_Delete(t *testing.T) {
p := NewMemPostings()
p.Add(1, labels.FromStrings("lbl1", "a"))
p.Add(2, labels.FromStrings("lbl1", "b"))
p.Add(3, labels.FromStrings("lbl2", "a"))
before := p.Get(allPostingsKey.Name, allPostingsKey.Value)
p.Delete(map[storage.SeriesRef]struct{}{
2: {},
})
after := p.Get(allPostingsKey.Name, allPostingsKey.Value)
// Make sure postings gotten before the delete have the old data when
// iterated over.
expanded, err := ExpandPostings(before)
require.NoError(t, err)
require.Equal(t, []storage.SeriesRef{1, 2, 3}, expanded)
// Make sure postings gotten after the delete have the new data when
// iterated over.
expanded, err = ExpandPostings(after)
require.NoError(t, err)
require.Equal(t, []storage.SeriesRef{1, 3}, expanded)
deleted := p.Get("lbl1", "b")
expanded, err = ExpandPostings(deleted)
require.NoError(t, err)
require.Equal(t, 0, len(expanded), "expected empty postings, got %v", expanded)
}