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
|
package lmdbscan_test
import (
"bytes"
"log"
"github.com/bmatsuo/lmdb-go/lmdb"
"github.com/bmatsuo/lmdb-go/lmdbscan"
)
var env *lmdb.Env
var dbi lmdb.DBI
// This example demonstrates basic usage of a Scanner to scan a database. It
// is important to always call scanner.Err() which will returned any unexpected
// error which interrupted scanner.Scan().
func ExampleScanner() {
err := env.View(func(txn *lmdb.Txn) (err error) {
scanner := lmdbscan.New(txn, dbi)
defer scanner.Close()
for scanner.Scan() {
log.Printf("k=%q v=%q", scanner.Key(), scanner.Val())
}
return scanner.Err()
})
if err != nil {
panic(err)
}
}
// This example demonstrates scanning a key range in a database. Set is used
// to move the cursor's starting position to the desired prefix.
func ExampleScanner_Set() {
keyprefix := []byte("users:")
err := env.View(func(txn *lmdb.Txn) (err error) {
scanner := lmdbscan.New(txn, dbi)
defer scanner.Close()
scanner.Set(keyprefix, nil, lmdb.SetRange)
for scanner.Scan() {
if !bytes.HasPrefix(scanner.Key(), keyprefix) {
break
}
log.Printf("k=%q v=%q", scanner.Key(), scanner.Val())
}
return scanner.Err()
})
if err != nil {
panic(err)
}
}
// This example demonstrates scanning all values for a key in a root database
// with the lmdb.DupSort flag set. SetNext is used instead of Set to configure
// Cursor the to return ErrNotFound (EOF) after all duplicate keys have been
// iterated.
func ExampleScanner_SetNext() {
key := []byte("userphone:123")
err := env.View(func(txn *lmdb.Txn) (err error) {
scanner := lmdbscan.New(txn, dbi)
defer scanner.Close()
scanner.SetNext(key, nil, lmdb.GetBothRange, lmdb.NextDup)
for scanner.Scan() {
log.Printf("k=%q v=%q", scanner.Key(), scanner.Val())
}
return scanner.Err()
})
if err != nil {
panic(err)
}
}
// This example demonstrates scanning all values for duplicate keys in a
// database with the lmdb.DupSort flag set. Two loops are used to iterate over
// unique keys and their values respectively. The example exploits the return
// value from SetNext as the termination condition for the first loop.
func ExampleScanner_SetNext_nextNoDup() {
err := env.View(func(txn *lmdb.Txn) (err error) {
scanner := lmdbscan.New(txn, dbi)
defer scanner.Close()
for scanner.SetNext(nil, nil, lmdb.NextNoDup, lmdb.NextDup) {
key := scanner.Key()
var vals [][]byte
for scanner.Scan() {
vals = append(vals, scanner.Val())
}
log.Printf("k=%q v=%q", key, vals)
if scanner.Err() != nil {
break
}
}
return scanner.Err()
})
if err != nil {
panic(err)
}
}
// This advanced example demonstrates batch scanning of values for duplicate
// keys in a database with the lmdb.DupFixed and lmdb.DupSort flags set. The
// outer loop scans unique keys and the inner loop scans duplicate values. The
// GetMultiple op requires an additional check following its use to determine
// if no duplicates exist in the database.
func ExampleScanner_SetNext_getMultiple() {
err := env.View(func(txn *lmdb.Txn) (err error) {
scanner := lmdbscan.New(txn, dbi)
defer scanner.Close()
for scanner.Set(nil, nil, lmdb.NextNoDup) {
key := scanner.Key()
valFirst := scanner.Val()
var vals [][]byte
if !scanner.SetNext(nil, nil, lmdb.GetMultiple, lmdb.NextMultiple) {
// only one value exists for the key, and it has been scanned.
vals = append(vals, valFirst)
}
for scanner.Scan() {
// this loop is only entered if multiple values exist for key.
multi := lmdb.WrapMulti(scanner.Val(), len(valFirst))
vals = append(vals, multi.Vals()...)
}
log.Printf("k=%q v=%q", key, vals)
if scanner.Err() != nil {
break
}
}
return scanner.Err()
})
if err != nil {
panic(err)
}
}
|
