Golang bolt.Open函数代码示例

// Ensure that a re-opened database is consistent.
func TestOpen_Check(t *testing.T) {
	path := tempfile()

	db, err := bolt.Open(path, 0666, nil)
	if err != nil {
		t.Fatal(err)
	}
	if err := db.View(func(tx *bolt.Tx) error { return <-tx.Check() }); err != nil {
		t.Fatal(err)
	}
	if err := db.Close(); err != nil {
		t.Fatal(err)
	}

	db, err = bolt.Open(path, 0666, nil)
	if err != nil {
		t.Fatal(err)
	}
	if err := db.View(func(tx *bolt.Tx) error { return <-tx.Check() }); err != nil {
		t.Fatal(err)
	}
	if err := db.Close(); err != nil {
		t.Fatal(err)
	}
}

// Ensure that opening an already open database file will wait until its closed.
func TestOpen_Wait(t *testing.T) {
	if runtime.GOOS == "solaris" {
		t.Skip("solaris fcntl locks don't support intra-process locking")
	}

	path := tempfile()

	// Open a data file.
	db0, err := bolt.Open(path, 0666, nil)
	if err != nil {
		t.Fatal(err)
	}

	// Close it in just a bit.
	time.AfterFunc(100*time.Millisecond, func() { _ = db0.Close() })

	// Attempt to open the database again.
	start := time.Now()
	db1, err := bolt.Open(path, 0666, &bolt.Options{Timeout: 200 * time.Millisecond})
	if err != nil {
		t.Fatal(err)
	} else if time.Since(start) <= 100*time.Millisecond {
		t.Fatal("expected to wait at least timeout duration")
	}

	if err := db1.Close(); err != nil {
		t.Fatal(err)
	}
}

func ExampleTx_CopyFile() {
	// Open the database.
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer os.Remove(db.Path())

	// Create a bucket and a key.
	if err := db.Update(func(tx *bolt.Tx) error {
		b, err := tx.CreateBucket([]byte("widgets"))
		if err != nil {
			return err
		}
		if err := b.Put([]byte("foo"), []byte("bar")); err != nil {
			return err
		}
		return nil
	}); err != nil {
		log.Fatal(err)
	}

	// Copy the database to another file.
	toFile := tempfile()
	if err := db.View(func(tx *bolt.Tx) error {
		return tx.CopyFile(toFile, 0666)
	}); err != nil {
		log.Fatal(err)
	}
	defer os.Remove(toFile)

	// Open the cloned database.
	db2, err := bolt.Open(toFile, 0666, nil)
	if err != nil {
		log.Fatal(err)
	}

	// Ensure that the key exists in the copy.
	if err := db2.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value for 'foo' in the clone is: %s\n", value)
		return nil
	}); err != nil {
		log.Fatal(err)
	}

	// Close database to release file lock.
	if err := db.Close(); err != nil {
		log.Fatal(err)
	}

	if err := db2.Close(); err != nil {
		log.Fatal(err)
	}

	// Output:
	// The value for 'foo' in the clone is: bar
}

// Run executes the command.
func (cmd *InfoCommand) Run(args ...string) error {
	// Parse flags.
	fs := flag.NewFlagSet("", flag.ContinueOnError)
	help := fs.Bool("h", false, "")
	if err := fs.Parse(args); err != nil {
		return err
	} else if *help {
		fmt.Fprintln(cmd.Stderr, cmd.Usage())
		return ErrUsage
	}

	// Require database path.
	path := fs.Arg(0)
	if path == "" {
		return ErrPathRequired
	} else if _, err := os.Stat(path); os.IsNotExist(err) {
		return ErrFileNotFound
	}

	// Open the database.
	db, err := bolt.Open(path, 0666, nil)
	if err != nil {
		return err
	}
	defer db.Close()

	// Print basic database info.
	info := db.Info()
	fmt.Fprintf(cmd.Stdout, "Page Size: %d\n", info.PageSize)

	return nil
}

// MustOpenDB returns a new, open DB at a temporary location.
func MustOpenDB() *DB {
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		panic(err)
	}
	return &DB{db}
}

func ExampleDB_Begin_ReadOnly() {
	// Open the database.
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer os.Remove(db.Path())

	// Create a bucket using a read-write transaction.
	if err := db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucket([]byte("widgets"))
		return err
	}); err != nil {
		log.Fatal(err)
	}

	// Create several keys in a transaction.
	tx, err := db.Begin(true)
	if err != nil {
		log.Fatal(err)
	}
	b := tx.Bucket([]byte("widgets"))
	if err := b.Put([]byte("john"), []byte("blue")); err != nil {
		log.Fatal(err)
	}
	if err := b.Put([]byte("abby"), []byte("red")); err != nil {
		log.Fatal(err)
	}
	if err := b.Put([]byte("zephyr"), []byte("purple")); err != nil {
		log.Fatal(err)
	}
	if err := tx.Commit(); err != nil {
		log.Fatal(err)
	}

	// Iterate over the values in sorted key order.
	tx, err = db.Begin(false)
	if err != nil {
		log.Fatal(err)
	}
	c := tx.Bucket([]byte("widgets")).Cursor()
	for k, v := c.First(); k != nil; k, v = c.Next() {
		fmt.Printf("%s likes %s\n", k, v)
	}

	if err := tx.Rollback(); err != nil {
		log.Fatal(err)
	}

	if err := db.Close(); err != nil {
		log.Fatal(err)
	}

	// Output:
	// abby likes red
	// john likes blue
	// zephyr likes purple
}

func ExampleBucket_Delete() {
	// Open the database.
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer os.Remove(db.Path())

	// Start a write transaction.
	if err := db.Update(func(tx *bolt.Tx) error {
		// Create a bucket.
		b, err := tx.CreateBucket([]byte("widgets"))
		if err != nil {
			return err
		}

		// Set the value "bar" for the key "foo".
		if err := b.Put([]byte("foo"), []byte("bar")); err != nil {
			return err
		}

		// Retrieve the key back from the database and verify it.
		value := b.Get([]byte("foo"))
		fmt.Printf("The value of 'foo' was: %s\n", value)

		return nil
	}); err != nil {
		log.Fatal(err)
	}

	// Delete the key in a different write transaction.
	if err := db.Update(func(tx *bolt.Tx) error {
		return tx.Bucket([]byte("widgets")).Delete([]byte("foo"))
	}); err != nil {
		log.Fatal(err)
	}

	// Retrieve the key again.
	if err := db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		if value == nil {
			fmt.Printf("The value of 'foo' is now: nil\n")
		}
		return nil
	}); err != nil {
		log.Fatal(err)
	}

	// Close database to release file lock.
	if err := db.Close(); err != nil {
		log.Fatal(err)
	}

	// Output:
	// The value of 'foo' was: bar
	// The value of 'foo' is now: nil
}

// Ensure that opening a database does not increase its size.
// https://github.com/boltdb/bolt/issues/291
func TestOpen_Size(t *testing.T) {
	// Open a data file.
	db := MustOpenDB()
	path := db.Path()
	defer db.MustClose()

	pagesize := db.Info().PageSize

	// Insert until we get above the minimum 4MB size.
	if err := db.Update(func(tx *bolt.Tx) error {
		b, _ := tx.CreateBucketIfNotExists([]byte("data"))
		for i := 0; i < 10000; i++ {
			if err := b.Put([]byte(fmt.Sprintf("%04d", i)), make([]byte, 1000)); err != nil {
				t.Fatal(err)
			}
		}
		return nil
	}); err != nil {
		t.Fatal(err)
	}

	// Close database and grab the size.
	if err := db.DB.Close(); err != nil {
		t.Fatal(err)
	}
	sz := fileSize(path)
	if sz == 0 {
		t.Fatalf("unexpected new file size: %d", sz)
	}

	// Reopen database, update, and check size again.
	db0, err := bolt.Open(path, 0666, nil)
	if err != nil {
		t.Fatal(err)
	}
	if err := db0.Update(func(tx *bolt.Tx) error {
		if err := tx.Bucket([]byte("data")).Put([]byte{0}, []byte{0}); err != nil {
			t.Fatal(err)
		}
		return nil
	}); err != nil {
		t.Fatal(err)
	}
	if err := db0.Close(); err != nil {
		t.Fatal(err)
	}
	newSz := fileSize(path)
	if newSz == 0 {
		t.Fatalf("unexpected new file size: %d", newSz)
	}

	// Compare the original size with the new size.
	// db size might increase by a few page sizes due to the new small update.
	if sz < newSz-5*int64(pagesize) {
		t.Fatalf("unexpected file growth: %d => %d", sz, newSz)
	}
}

// TestDB_Open_InitialMmapSize tests if having InitialMmapSize large enough
// to hold data from concurrent write transaction resolves the issue that
// read transaction blocks the write transaction and causes deadlock.
// This is a very hacky test since the mmap size is not exposed.
func TestDB_Open_InitialMmapSize(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	initMmapSize := 1 << 31  // 2GB
	testWriteSize := 1 << 27 // 134MB

	db, err := bolt.Open(path, 0666, &bolt.Options{InitialMmapSize: initMmapSize})
	if err != nil {
		t.Fatal(err)
	}

	// create a long-running read transaction
	// that never gets closed while writing
	rtx, err := db.Begin(false)
	if err != nil {
		t.Fatal(err)
	}

	// create a write transaction
	wtx, err := db.Begin(true)
	if err != nil {
		t.Fatal(err)
	}

	b, err := wtx.CreateBucket([]byte("test"))
	if err != nil {
		t.Fatal(err)
	}

	// and commit a large write
	err = b.Put([]byte("foo"), make([]byte, testWriteSize))
	if err != nil {
		t.Fatal(err)
	}

	done := make(chan struct{})

	go func() {
		if err := wtx.Commit(); err != nil {
			t.Fatal(err)
		}
		done <- struct{}{}
	}()

	select {
	case <-time.After(5 * time.Second):
		t.Errorf("unexpected that the reader blocks writer")
	case <-done:
	}

	if err := rtx.Rollback(); err != nil {
		t.Fatal(err)
	}
}

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.
}

// MustOpen creates a Bolt database in a temporary location.
func MustOpen(mode os.FileMode, options *bolt.Options) *DB {
	// Create temporary path.
	f, _ := ioutil.TempFile("", "bolt-")
	f.Close()
	os.Remove(f.Name())

	db, err := bolt.Open(f.Name(), mode, options)
	if err != nil {
		panic(err.Error())
	}
	return &DB{DB: db, Path: f.Name()}
}

// Ensure that a database that is too small returns an error.
func TestOpen_FileTooSmall(t *testing.T) {
	path := tempfile()

	db, err := bolt.Open(path, 0666, nil)
	if err != nil {
		t.Fatal(err)
	}
	if err := db.Close(); err != nil {
		t.Fatal(err)
	}

	// corrupt the database
	if err := os.Truncate(path, int64(os.Getpagesize())); err != nil {
		t.Fatal(err)
	}

	db, err = bolt.Open(path, 0666, nil)
	if err == nil || err.Error() != "file size too small" {
		t.Fatalf("unexpected error: %s", err)
	}
}

func ExampleTx_Rollback() {
	// Open the database.
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer os.Remove(db.Path())

	// Create a bucket.
	if err := db.Update(func(tx *bolt.Tx) error {
		_, err := tx.CreateBucket([]byte("widgets"))
		return err
	}); err != nil {
		log.Fatal(err)
	}

	// Set a value for a key.
	if err := db.Update(func(tx *bolt.Tx) error {
		return tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
	}); err != nil {
		log.Fatal(err)
	}

	// Update the key but rollback the transaction so it never saves.
	tx, err := db.Begin(true)
	if err != nil {
		log.Fatal(err)
	}
	b := tx.Bucket([]byte("widgets"))
	if err := b.Put([]byte("foo"), []byte("baz")); err != nil {
		log.Fatal(err)
	}
	if err := tx.Rollback(); err != nil {
		log.Fatal(err)
	}

	// Ensure that our original value is still set.
	if err := db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value for 'foo' is still: %s\n", value)
		return nil
	}); err != nil {
		log.Fatal(err)
	}

	// Close database to release file lock.
	if err := db.Close(); err != nil {
		log.Fatal(err)
	}

	// Output:
	// The value for 'foo' is still: bar
}

// Ensure that the database can be copied to a file path.
func TestTx_CopyFile(t *testing.T) {
	db := MustOpenDB()
	defer db.MustClose()

	path := tempfile()
	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("bar")); err != nil {
			t.Fatal(err)
		}
		if err := b.Put([]byte("baz"), []byte("bat")); err != nil {
			t.Fatal(err)
		}
		return nil
	}); err != nil {
		t.Fatal(err)
	}

	if err := db.View(func(tx *bolt.Tx) error {
		return tx.CopyFile(path, 0600)
	}); err != nil {
		t.Fatal(err)
	}

	db2, err := bolt.Open(path, 0600, nil)
	if err != nil {
		t.Fatal(err)
	}

	if err := db2.View(func(tx *bolt.Tx) error {
		if v := tx.Bucket([]byte("widgets")).Get([]byte("foo")); !bytes.Equal(v, []byte("bar")) {
			t.Fatalf("unexpected value: %v", v)
		}
		if v := tx.Bucket([]byte("widgets")).Get([]byte("baz")); !bytes.Equal(v, []byte("bat")) {
			t.Fatalf("unexpected value: %v", v)
		}
		return nil
	}); err != nil {
		t.Fatal(err)
	}

	if err := db2.Close(); err != nil {
		t.Fatal(err)
	}
}

func ExampleBucket_ForEach() {
	// Open the database.
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer os.Remove(db.Path())

	// Insert data into a bucket.
	if err := db.Update(func(tx *bolt.Tx) error {
		b, err := tx.CreateBucket([]byte("animals"))
		if err != nil {
			return err
		}

		if err := b.Put([]byte("dog"), []byte("fun")); err != nil {
			return err
		}
		if err := b.Put([]byte("cat"), []byte("lame")); err != nil {
			return err
		}
		if err := b.Put([]byte("liger"), []byte("awesome")); err != nil {
			return err
		}

		// Iterate over items in sorted key order.
		if err := b.ForEach(func(k, v []byte) error {
			fmt.Printf("A %s is %s.\n", k, v)
			return nil
		}); err != nil {
			return err
		}

		return nil
	}); err != nil {
		log.Fatal(err)
	}

	// Close database to release file lock.
	if err := db.Close(); err != nil {
		log.Fatal(err)
	}

	// Output:
	// A cat is lame.
	// A dog is fun.
	// A liger is awesome.
}