github.com/cockroachdb/pebble@v1.1.1-0.20240513155919-3622ade60459/iterator_example_test.go (about) 1 // Copyright 2021 The LevelDB-Go and Pebble Authors. All rights reserved. Use 2 // of this source code is governed by a BSD-style license that can be found in 3 // the LICENSE file. 4 5 package pebble_test 6 7 import ( 8 "fmt" 9 "log" 10 11 "github.com/cockroachdb/pebble" 12 "github.com/cockroachdb/pebble/vfs" 13 ) 14 15 func ExampleIterator() { 16 db, err := pebble.Open("", &pebble.Options{FS: vfs.NewMem()}) 17 if err != nil { 18 log.Fatal(err) 19 } 20 21 keys := []string{"hello", "world", "hello world"} 22 for _, key := range keys { 23 if err := db.Set([]byte(key), nil, pebble.Sync); err != nil { 24 log.Fatal(err) 25 } 26 } 27 28 iter, _ := db.NewIter(nil) 29 for iter.First(); iter.Valid(); iter.Next() { 30 fmt.Printf("%s\n", iter.Key()) 31 } 32 if err := iter.Close(); err != nil { 33 log.Fatal(err) 34 } 35 if err := db.Close(); err != nil { 36 log.Fatal(err) 37 } 38 // Output: 39 // hello 40 // hello world 41 // world 42 } 43 44 func ExampleIterator_prefixIteration() { 45 db, err := pebble.Open("", &pebble.Options{FS: vfs.NewMem()}) 46 if err != nil { 47 log.Fatal(err) 48 } 49 50 keyUpperBound := func(b []byte) []byte { 51 end := make([]byte, len(b)) 52 copy(end, b) 53 for i := len(end) - 1; i >= 0; i-- { 54 end[i] = end[i] + 1 55 if end[i] != 0 { 56 return end[:i+1] 57 } 58 } 59 return nil // no upper-bound 60 } 61 62 prefixIterOptions := func(prefix []byte) *pebble.IterOptions { 63 return &pebble.IterOptions{ 64 LowerBound: prefix, 65 UpperBound: keyUpperBound(prefix), 66 } 67 } 68 69 keys := []string{"hello", "world", "hello world"} 70 for _, key := range keys { 71 if err := db.Set([]byte(key), nil, pebble.Sync); err != nil { 72 log.Fatal(err) 73 } 74 } 75 76 iter, _ := db.NewIter(prefixIterOptions([]byte("hello"))) 77 for iter.First(); iter.Valid(); iter.Next() { 78 fmt.Printf("%s\n", iter.Key()) 79 } 80 if err := iter.Close(); err != nil { 81 log.Fatal(err) 82 } 83 if err := db.Close(); err != nil { 84 log.Fatal(err) 85 } 86 // Output: 87 // hello 88 // hello world 89 } 90 91 func ExampleIterator_SeekGE() { 92 db, err := pebble.Open("", &pebble.Options{FS: vfs.NewMem()}) 93 if err != nil { 94 log.Fatal(err) 95 } 96 97 keys := []string{"hello", "world", "hello world"} 98 for _, key := range keys { 99 if err := db.Set([]byte(key), nil, pebble.Sync); err != nil { 100 log.Fatal(err) 101 } 102 } 103 104 iter, _ := db.NewIter(nil) 105 if iter.SeekGE([]byte("a")); iter.Valid() { 106 fmt.Printf("%s\n", iter.Key()) 107 } 108 if iter.SeekGE([]byte("hello w")); iter.Valid() { 109 fmt.Printf("%s\n", iter.Key()) 110 } 111 if iter.SeekGE([]byte("w")); iter.Valid() { 112 fmt.Printf("%s\n", iter.Key()) 113 } 114 if err := iter.Close(); err != nil { 115 log.Fatal(err) 116 } 117 if err := db.Close(); err != nil { 118 log.Fatal(err) 119 } 120 // Output: 121 // hello 122 // hello world 123 // world 124 }