/
merge_iter.go
275 lines (242 loc) · 5.2 KB
/
merge_iter.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
package db
//合并两个迭代器成一个迭代器
import (
"errors"
"github.com/syndtr/goleveldb/leveldb/comparer"
)
type dir int
const (
dirReleased dir = iota - 1
dirSOI
dirEOI
dirForward
dirSeek
)
//合并错误列表
var (
ErrIterReleased = errors.New("ErrIterReleased")
)
type mergedIterator struct {
itBase
cmp comparer.Comparer
iters []Iterator
strict bool
reverse bool
keys [][]byte
prevKey []byte
index int
dir dir
err error
}
func assertKey(key []byte) []byte {
if key == nil {
panic("leveldb/iterator: nil key")
}
return key
}
func (i *mergedIterator) iterErr(iter Iterator) bool {
if err := iter.Error(); err != nil {
if i.strict {
i.err = err
return true
}
}
return false
}
func (i *mergedIterator) Valid() bool {
return i.err == nil && i.dir > dirEOI
}
func (i *mergedIterator) Rewind() bool {
if i.err != nil {
return false
} else if i.dir == dirReleased {
i.err = ErrIterReleased
return false
}
for x, iter := range i.iters {
switch {
case iter.Rewind():
i.keys[x] = assertKey(iter.Key())
case i.iterErr(iter):
return false
default:
i.keys[x] = nil
}
}
i.dir = dirSOI
return i.selectKey()
}
func (i *mergedIterator) Seek(key []byte) bool {
if i.err != nil {
return false
} else if i.dir == dirReleased {
i.err = ErrIterReleased
return false
}
for x, iter := range i.iters {
switch {
case iter.Seek(key):
i.keys[x] = assertKey(iter.Key())
case i.iterErr(iter):
return false
default:
i.keys[x] = nil
}
}
i.dir = dirSOI
if i.selectKey() {
i.dir = dirSeek
return true
}
i.dir = dirSOI
return false
}
func (i *mergedIterator) compare(key1 []byte, key2 []byte) int {
if key1 == nil && key2 != nil {
return 1
}
if key1 != nil && key2 == nil {
return -1
}
result := i.cmp.Compare(key1, key2)
if i.reverse {
return -result
}
return result
}
func (i *mergedIterator) selectKey() bool {
var key []byte
for x, tkey := range i.keys {
if tkey != nil && (key == nil || i.compare(tkey, key) < 0) {
key = tkey
i.index = x
}
}
if key == nil {
i.dir = dirEOI
return false
}
if i.dir == dirSOI {
i.prevKey = cloneByte(key)
}
i.dir = dirForward
return true
}
// Next next key
func (i *mergedIterator) Next() bool {
for {
// 首次next, 需要对内部各迭代器都重置
if i.dir == dirSOI {
return i.Rewind()
}
if !i.next() {
return false
}
currKey := i.Key()
if i.compare(currKey, i.prevKey) != 0 {
i.updatePrevKey(currKey)
return true
}
}
}
func (i *mergedIterator) updatePrevKey(currKey []byte) {
if cap(i.prevKey) < len(currKey) {
i.prevKey = make([]byte, len(currKey))
}
i.prevKey = i.prevKey[:len(currKey)]
copy(i.prevKey, currKey)
}
func (i *mergedIterator) next() bool {
if i.dir == dirEOI || i.err != nil {
return false
} else if i.dir == dirReleased {
i.err = ErrIterReleased
return false
}
x := i.index
iter := i.iters[x]
switch {
case iter.Next():
i.keys[x] = assertKey(iter.Key())
case i.iterErr(iter):
return false
default:
i.keys[x] = nil
}
return i.selectKey()
}
func (i *mergedIterator) Key() []byte {
if i.err != nil || i.dir <= dirEOI {
return nil
}
return i.keys[i.index]
}
func (i *mergedIterator) Value() []byte {
if i.err != nil || i.dir <= dirEOI {
return nil
}
return i.iters[i.index].Value()
}
func (i *mergedIterator) ValueCopy() []byte {
if i.err != nil || i.dir <= dirEOI {
return nil
}
v := i.iters[i.index].Value()
return cloneByte(v)
}
func (i *mergedIterator) Close() {
if i.dir != dirReleased {
i.dir = dirReleased
for _, iter := range i.iters {
iter.Close()
}
i.iters = nil
i.keys = nil
}
}
func (i *mergedIterator) Error() error {
return i.err
}
// NewMergedIterator returns an iterator that merges its input. Walking the
// resultant iterator will return all key/value pairs of all input iterators
// in strictly increasing key order, as defined by cmp.
// The input's key ranges may overlap, but there are assumed to be no duplicate
// keys: if iters[i] contains a key k then iters[j] will not contain that key k.
// None of the iters may be nil.
//
// If strict is true the any 'corruption errors' (i.e errors.IsCorrupted(err) == true)
// won't be ignored and will halt 'merged iterator', otherwise the iterator will
// continue to the next 'input iterator'.
func NewMergedIterator(iters []Iterator) Iterator {
reverse := true
if len(iters) >= 2 {
reverse = iters[0].IsReverse()
for i := 1; i < len(iters); i++ {
if reverse != iters[i].IsReverse() {
panic("merge iter not support diff reverse flag")
}
}
}
return &mergedIterator{
iters: iters,
reverse: reverse,
cmp: comparer.DefaultComparer,
strict: true,
keys: make([][]byte, len(iters)),
prevKey: make([]byte, 128),
}
}
type mergedIteratorDB struct {
iters []IteratorDB
}
//NewMergedIteratorDB 合并两个迭代数据库
func NewMergedIteratorDB(iters []IteratorDB) IteratorDB {
return &mergedIteratorDB{iters: iters}
}
func (merge *mergedIteratorDB) Iterator(start []byte, end []byte, reverse bool) Iterator {
iters := make([]Iterator, len(merge.iters))
for i := 0; i < len(merge.iters); i++ {
iters[i] = merge.iters[i].Iterator(start, end, reverse)
}
return NewMergedIterator(iters)
}