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-rw-r--r--tests/cursor_test.go817
1 files changed, 817 insertions, 0 deletions
diff --git a/tests/cursor_test.go b/tests/cursor_test.go
new file mode 100644
index 0000000..562d60f
--- /dev/null
+++ b/tests/cursor_test.go
@@ -0,0 +1,817 @@
+package bolt_test
+
+import (
+ "bytes"
+ "encoding/binary"
+ "fmt"
+ "log"
+ "os"
+ "reflect"
+ "sort"
+ "testing"
+ "testing/quick"
+
+ "github.com/boltdb/bolt"
+)
+
+// Ensure that a cursor can return a reference to the bucket that created it.
+func TestCursor_Bucket(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if cb := b.Cursor().Bucket(); !reflect.DeepEqual(cb, b) {
+ t.Fatal("cursor bucket mismatch")
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can seek to the appropriate keys.
+func TestCursor_Seek(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("foo"), []byte("0001")); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("bar"), []byte("0002")); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("baz"), []byte("0003")); err != nil {
+ t.Fatal(err)
+ }
+
+ if _, err := b.CreateBucket([]byte("bkt")); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.View(func(tx *bolt.Tx) error {
+ c := tx.Bucket([]byte("widgets")).Cursor()
+
+ // Exact match should go to the key.
+ if k, v := c.Seek([]byte("bar")); !bytes.Equal(k, []byte("bar")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte("0002")) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ // Inexact match should go to the next key.
+ if k, v := c.Seek([]byte("bas")); !bytes.Equal(k, []byte("baz")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte("0003")) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ // Low key should go to the first key.
+ if k, v := c.Seek([]byte("")); !bytes.Equal(k, []byte("bar")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte("0002")) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ // High key should return no key.
+ if k, v := c.Seek([]byte("zzz")); k != nil {
+ t.Fatalf("expected nil key: %v", k)
+ } else if v != nil {
+ t.Fatalf("expected nil value: %v", v)
+ }
+
+ // Buckets should return their key but no value.
+ if k, v := c.Seek([]byte("bkt")); !bytes.Equal(k, []byte("bkt")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if v != nil {
+ t.Fatalf("expected nil value: %v", v)
+ }
+
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+func TestCursor_Delete(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ const count = 1000
+
+ // Insert every other key between 0 and $count.
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ for i := 0; i < count; i += 1 {
+ k := make([]byte, 8)
+ binary.BigEndian.PutUint64(k, uint64(i))
+ if err := b.Put(k, make([]byte, 100)); err != nil {
+ t.Fatal(err)
+ }
+ }
+ if _, err := b.CreateBucket([]byte("sub")); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ bound := make([]byte, 8)
+ binary.BigEndian.PutUint64(bound, uint64(count/2))
+ for key, _ := c.First(); bytes.Compare(key, bound) < 0; key, _ = c.Next() {
+ if err := c.Delete(); err != nil {
+ t.Fatal(err)
+ }
+ }
+
+ c.Seek([]byte("sub"))
+ if err := c.Delete(); err != bolt.ErrIncompatibleValue {
+ t.Fatalf("unexpected error: %s", err)
+ }
+
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.View(func(tx *bolt.Tx) error {
+ stats := tx.Bucket([]byte("widgets")).Stats()
+ if stats.KeyN != count/2+1 {
+ t.Fatalf("unexpected KeyN: %d", stats.KeyN)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can seek to the appropriate keys when there are a
+// large number of keys. This test also checks that seek will always move
+// forward to the next key.
+//
+// Related: https://github.com/boltdb/bolt/pull/187
+func TestCursor_Seek_Large(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ var count = 10000
+
+ // Insert every other key between 0 and $count.
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ for i := 0; i < count; i += 100 {
+ for j := i; j < i+100; j += 2 {
+ k := make([]byte, 8)
+ binary.BigEndian.PutUint64(k, uint64(j))
+ if err := b.Put(k, make([]byte, 100)); err != nil {
+ t.Fatal(err)
+ }
+ }
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.View(func(tx *bolt.Tx) error {
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ for i := 0; i < count; i++ {
+ seek := make([]byte, 8)
+ binary.BigEndian.PutUint64(seek, uint64(i))
+
+ k, _ := c.Seek(seek)
+
+ // The last seek is beyond the end of the the range so
+ // it should return nil.
+ if i == count-1 {
+ if k != nil {
+ t.Fatal("expected nil key")
+ }
+ continue
+ }
+
+ // Otherwise we should seek to the exact key or the next key.
+ num := binary.BigEndian.Uint64(k)
+ if i%2 == 0 {
+ if num != uint64(i) {
+ t.Fatalf("unexpected num: %d", num)
+ }
+ } else {
+ if num != uint64(i+1) {
+ t.Fatalf("unexpected num: %d", num)
+ }
+ }
+ }
+
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a cursor can iterate over an empty bucket without error.
+func TestCursor_EmptyBucket(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+ if err := db.Update(func(tx *bolt.Tx) error {
+ _, err := tx.CreateBucket([]byte("widgets"))
+ return err
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.View(func(tx *bolt.Tx) error {
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ k, v := c.First()
+ if k != nil {
+ t.Fatalf("unexpected key: %v", k)
+ } else if v != nil {
+ t.Fatalf("unexpected value: %v", v)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can reverse iterate over an empty bucket without error.
+func TestCursor_EmptyBucketReverse(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ _, err := tx.CreateBucket([]byte("widgets"))
+ return err
+ }); err != nil {
+ t.Fatal(err)
+ }
+ if err := db.View(func(tx *bolt.Tx) error {
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ k, v := c.Last()
+ if k != nil {
+ t.Fatalf("unexpected key: %v", k)
+ } else if v != nil {
+ t.Fatalf("unexpected value: %v", v)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can iterate over a single root with a couple elements.
+func TestCursor_Iterate_Leaf(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("baz"), []byte{}); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("foo"), []byte{0}); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("bar"), []byte{1}); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+ tx, err := db.Begin(false)
+ if err != nil {
+ t.Fatal(err)
+ }
+ defer func() { _ = tx.Rollback() }()
+
+ c := tx.Bucket([]byte("widgets")).Cursor()
+
+ k, v := c.First()
+ if !bytes.Equal(k, []byte("bar")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte{1}) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ k, v = c.Next()
+ if !bytes.Equal(k, []byte("baz")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte{}) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ k, v = c.Next()
+ if !bytes.Equal(k, []byte("foo")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte{0}) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ k, v = c.Next()
+ if k != nil {
+ t.Fatalf("expected nil key: %v", k)
+ } else if v != nil {
+ t.Fatalf("expected nil value: %v", v)
+ }
+
+ k, v = c.Next()
+ if k != nil {
+ t.Fatalf("expected nil key: %v", k)
+ } else if v != nil {
+ t.Fatalf("expected nil value: %v", v)
+ }
+
+ if err := tx.Rollback(); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can iterate in reverse over a single root with a couple elements.
+func TestCursor_LeafRootReverse(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("baz"), []byte{}); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("foo"), []byte{0}); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("bar"), []byte{1}); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+ tx, err := db.Begin(false)
+ if err != nil {
+ t.Fatal(err)
+ }
+ c := tx.Bucket([]byte("widgets")).Cursor()
+
+ if k, v := c.Last(); !bytes.Equal(k, []byte("foo")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte{0}) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ if k, v := c.Prev(); !bytes.Equal(k, []byte("baz")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte{}) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ if k, v := c.Prev(); !bytes.Equal(k, []byte("bar")) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, []byte{1}) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+
+ if k, v := c.Prev(); k != nil {
+ t.Fatalf("expected nil key: %v", k)
+ } else if v != nil {
+ t.Fatalf("expected nil value: %v", v)
+ }
+
+ if k, v := c.Prev(); k != nil {
+ t.Fatalf("expected nil key: %v", k)
+ } else if v != nil {
+ t.Fatalf("expected nil value: %v", v)
+ }
+
+ if err := tx.Rollback(); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can restart from the beginning.
+func TestCursor_Restart(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("bar"), []byte{}); err != nil {
+ t.Fatal(err)
+ }
+ if err := b.Put([]byte("foo"), []byte{}); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ tx, err := db.Begin(false)
+ if err != nil {
+ t.Fatal(err)
+ }
+ c := tx.Bucket([]byte("widgets")).Cursor()
+
+ if k, _ := c.First(); !bytes.Equal(k, []byte("bar")) {
+ t.Fatalf("unexpected key: %v", k)
+ }
+ if k, _ := c.Next(); !bytes.Equal(k, []byte("foo")) {
+ t.Fatalf("unexpected key: %v", k)
+ }
+
+ if k, _ := c.First(); !bytes.Equal(k, []byte("bar")) {
+ t.Fatalf("unexpected key: %v", k)
+ }
+ if k, _ := c.Next(); !bytes.Equal(k, []byte("foo")) {
+ t.Fatalf("unexpected key: %v", k)
+ }
+
+ if err := tx.Rollback(); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a cursor can skip over empty pages that have been deleted.
+func TestCursor_First_EmptyPages(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ // Create 1000 keys in the "widgets" bucket.
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ for i := 0; i < 1000; i++ {
+ if err := b.Put(u64tob(uint64(i)), []byte{}); err != nil {
+ t.Fatal(err)
+ }
+ }
+
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ // Delete half the keys and then try to iterate.
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b := tx.Bucket([]byte("widgets"))
+ for i := 0; i < 600; i++ {
+ if err := b.Delete(u64tob(uint64(i))); err != nil {
+ t.Fatal(err)
+ }
+ }
+
+ c := b.Cursor()
+ var n int
+ for k, _ := c.First(); k != nil; k, _ = c.Next() {
+ n++
+ }
+ if n != 400 {
+ t.Fatalf("unexpected key count: %d", n)
+ }
+
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx can iterate over all elements in a bucket.
+func TestCursor_QuickCheck(t *testing.T) {
+ f := func(items testdata) bool {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ // Bulk insert all values.
+ tx, err := db.Begin(true)
+ if err != nil {
+ t.Fatal(err)
+ }
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ for _, item := range items {
+ if err := b.Put(item.Key, item.Value); err != nil {
+ t.Fatal(err)
+ }
+ }
+ if err := tx.Commit(); err != nil {
+ t.Fatal(err)
+ }
+
+ // Sort test data.
+ sort.Sort(items)
+
+ // Iterate over all items and check consistency.
+ var index = 0
+ tx, err = db.Begin(false)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ for k, v := c.First(); k != nil && index < len(items); k, v = c.Next() {
+ if !bytes.Equal(k, items[index].Key) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, items[index].Value) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+ index++
+ }
+ if len(items) != index {
+ t.Fatalf("unexpected item count: %v, expected %v", len(items), index)
+ }
+
+ if err := tx.Rollback(); err != nil {
+ t.Fatal(err)
+ }
+
+ return true
+ }
+ if err := quick.Check(f, qconfig()); err != nil {
+ t.Error(err)
+ }
+}
+
+// Ensure that a transaction can iterate over all elements in a bucket in reverse.
+func TestCursor_QuickCheck_Reverse(t *testing.T) {
+ f := func(items testdata) bool {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ // Bulk insert all values.
+ tx, err := db.Begin(true)
+ if err != nil {
+ t.Fatal(err)
+ }
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ for _, item := range items {
+ if err := b.Put(item.Key, item.Value); err != nil {
+ t.Fatal(err)
+ }
+ }
+ if err := tx.Commit(); err != nil {
+ t.Fatal(err)
+ }
+
+ // Sort test data.
+ sort.Sort(revtestdata(items))
+
+ // Iterate over all items and check consistency.
+ var index = 0
+ tx, err = db.Begin(false)
+ if err != nil {
+ t.Fatal(err)
+ }
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ for k, v := c.Last(); k != nil && index < len(items); k, v = c.Prev() {
+ if !bytes.Equal(k, items[index].Key) {
+ t.Fatalf("unexpected key: %v", k)
+ } else if !bytes.Equal(v, items[index].Value) {
+ t.Fatalf("unexpected value: %v", v)
+ }
+ index++
+ }
+ if len(items) != index {
+ t.Fatalf("unexpected item count: %v, expected %v", len(items), index)
+ }
+
+ if err := tx.Rollback(); err != nil {
+ t.Fatal(err)
+ }
+
+ return true
+ }
+ if err := quick.Check(f, qconfig()); err != nil {
+ t.Error(err)
+ }
+}
+
+// Ensure that a Tx cursor can iterate over subbuckets.
+func TestCursor_QuickCheck_BucketsOnly(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if _, err := b.CreateBucket([]byte("foo")); err != nil {
+ t.Fatal(err)
+ }
+ if _, err := b.CreateBucket([]byte("bar")); err != nil {
+ t.Fatal(err)
+ }
+ if _, err := b.CreateBucket([]byte("baz")); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.View(func(tx *bolt.Tx) error {
+ var names []string
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ for k, v := c.First(); k != nil; k, v = c.Next() {
+ names = append(names, string(k))
+ if v != nil {
+ t.Fatalf("unexpected value: %v", v)
+ }
+ }
+ if !reflect.DeepEqual(names, []string{"bar", "baz", "foo"}) {
+ t.Fatalf("unexpected names: %+v", names)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+// Ensure that a Tx cursor can reverse iterate over subbuckets.
+func TestCursor_QuickCheck_BucketsOnly_Reverse(t *testing.T) {
+ db := MustOpenDB()
+ defer db.MustClose()
+
+ if err := db.Update(func(tx *bolt.Tx) error {
+ b, err := tx.CreateBucket([]byte("widgets"))
+ if err != nil {
+ t.Fatal(err)
+ }
+ if _, err := b.CreateBucket([]byte("foo")); err != nil {
+ t.Fatal(err)
+ }
+ if _, err := b.CreateBucket([]byte("bar")); err != nil {
+ t.Fatal(err)
+ }
+ if _, err := b.CreateBucket([]byte("baz")); err != nil {
+ t.Fatal(err)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+
+ if err := db.View(func(tx *bolt.Tx) error {
+ var names []string
+ c := tx.Bucket([]byte("widgets")).Cursor()
+ for k, v := c.Last(); k != nil; k, v = c.Prev() {
+ names = append(names, string(k))
+ if v != nil {
+ t.Fatalf("unexpected value: %v", v)
+ }
+ }
+ if !reflect.DeepEqual(names, []string{"foo", "baz", "bar"}) {
+ t.Fatalf("unexpected names: %+v", names)
+ }
+ return nil
+ }); err != nil {
+ t.Fatal(err)
+ }
+}
+
+func ExampleCursor() {
+ // Open the database.
+ db, err := bolt.Open(tempfile(), 0666, nil)
+ if err != nil {
+ log.Fatal(err)
+ }
+ defer os.Remove(db.Path())
+
+ // Start a read-write transaction.
+ if err := db.Update(func(tx *bolt.Tx) error {
+ // Create a new bucket.
+ b, err := tx.CreateBucket([]byte("animals"))
+ if err != nil {
+ return err
+ }
+
+ // Insert data into a bucket.
+ if err := b.Put([]byte("dog"), []byte("fun")); err != nil {
+ log.Fatal(err)
+ }
+ if err := b.Put([]byte("cat"), []byte("lame")); err != nil {
+ log.Fatal(err)
+ }
+ if err := b.Put([]byte("liger"), []byte("awesome")); err != nil {
+ log.Fatal(err)
+ }
+
+ // Create a cursor for iteration.
+ c := b.Cursor()
+
+ // Iterate over items in sorted key order. This starts from the
+ // first key/value pair and updates the k/v variables to the
+ // next key/value on each iteration.
+ //
+ // The loop finishes at the end of the cursor when a nil key is returned.
+ for k, v := c.First(); k != nil; k, v = c.Next() {
+ fmt.Printf("A %s is %s.\n", k, v)
+ }
+
+ return nil
+ }); err != nil {
+ log.Fatal(err)
+ }
+
+ if err := db.Close(); err != nil {
+ log.Fatal(err)
+ }
+
+ // Output:
+ // A cat is lame.
+ // A dog is fun.
+ // A liger is awesome.
+}
+
+func ExampleCursor_reverse() {
+ // Open the database.
+ db, err := bolt.Open(tempfile(), 0666, nil)
+ if err != nil {
+ log.Fatal(err)
+ }
+ defer os.Remove(db.Path())
+
+ // Start a read-write transaction.
+ if err := db.Update(func(tx *bolt.Tx) error {
+ // Create a new bucket.
+ b, err := tx.CreateBucket([]byte("animals"))
+ if err != nil {
+ return err
+ }
+
+ // Insert data into a bucket.
+ if err := b.Put([]byte("dog"), []byte("fun")); err != nil {
+ log.Fatal(err)
+ }
+ if err := b.Put([]byte("cat"), []byte("lame")); err != nil {
+ log.Fatal(err)
+ }
+ if err := b.Put([]byte("liger"), []byte("awesome")); err != nil {
+ log.Fatal(err)
+ }
+
+ // Create a cursor for iteration.
+ c := b.Cursor()
+
+ // Iterate over items in reverse sorted key order. This starts
+ // from the last key/value pair and updates the k/v variables to
+ // the previous key/value on each iteration.
+ //
+ // The loop finishes at the beginning of the cursor when a nil key
+ // is returned.
+ for k, v := c.Last(); k != nil; k, v = c.Prev() {
+ fmt.Printf("A %s is %s.\n", k, v)
+ }
+
+ return nil
+ }); err != nil {
+ log.Fatal(err)
+ }
+
+ // Close the database to release the file lock.
+ if err := db.Close(); err != nil {
+ log.Fatal(err)
+ }
+
+ // Output:
+ // A liger is awesome.
+ // A dog is fun.
+ // A cat is lame.
+}