Golang bolt.Open函数代码示例

func ExampleTx_CopyFile() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Create a bucket and a key.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("widgets"))
		tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
		return nil
	})

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

	// Open the cloned database.
	db2, _ := bolt.Open(toFile, 0666, nil)
	defer db2.Close()

	// Ensure that the key exists in the copy.
	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
	})

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

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

	db, err := bolt.Open(path, 0666, nil)
	ok(t, err)
	db.Close()

	// corrupt the database
	ok(t, os.Truncate(path, int64(os.Getpagesize())))

	db, err = bolt.Open(path, 0666, nil)
	equals(t, errors.New("file size too small"), err)
}

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

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

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

// NewTestDB returns a new instance of TestDB.
func NewTestDB() *TestDB {
	db, err := bolt.Open(tempfile(), 0666, nil)
	if err != nil {
		panic("cannot open db: " + err.Error())
	}
	return &TestDB{db}
}

func ExampleBucket_ForEach() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Insert data into a bucket.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("animals"))
		b := tx.Bucket([]byte("animals"))
		b.Put([]byte("dog"), []byte("fun"))
		b.Put([]byte("cat"), []byte("lame"))
		b.Put([]byte("liger"), []byte("awesome"))

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

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

func ExampleBucket_Put() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Start a write transaction.
	db.Update(func(tx *bolt.Tx) error {
		// Create a bucket.
		tx.CreateBucket([]byte("widgets"))

		// Set the value "bar" for the key "foo".
		tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
		return nil
	})

	// Read value back in a different read-only transaction.
	db.View(func(tx *bolt.Tx) error {
		value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
		fmt.Printf("The value of 'foo' is: %s\n", value)
		return nil
	})

	// Output:
	// The value of 'foo' is: bar
}

// Keys retrieves a list of keys for a given bucket.
func Keys(path, name string) {
	if _, err := os.Stat(path); os.IsNotExist(err) {
		fatal(err)
		return
	}

	db, err := bolt.Open(path, 0600, nil)
	if err != nil {
		fatal(err)
		return
	}
	defer db.Close()

	err = db.View(func(tx *bolt.Tx) error {
		// Find bucket.
		b := tx.Bucket([]byte(name))
		if b == nil {
			fatalf("bucket not found: %s", name)
			return nil
		}

		// Iterate over each key.
		return b.ForEach(func(key, _ []byte) error {
			println(string(key))
			return nil
		})
	})
	if err != nil {
		fatal(err)
		return
	}
}

func ExampleTx_Rollback() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

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

	// Set a value for a key.
	db.Update(func(tx *bolt.Tx) error {
		return tx.Bucket([]byte("widgets")).Put([]byte("foo"), []byte("bar"))
	})

	// Update the key but rollback the transaction so it never saves.
	tx, _ := db.Begin(true)
	b := tx.Bucket([]byte("widgets"))
	b.Put([]byte("foo"), []byte("baz"))
	tx.Rollback()

	// Ensure that our original value is still set.
	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
	})

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

func ExampleDB_Update() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Execute several commands within a write transaction.
	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
	})

	// If our transactional block didn't return an error then our data is saved.
	if err == nil {
		db.View(func(tx *bolt.Tx) error {
			value := tx.Bucket([]byte("widgets")).Get([]byte("foo"))
			fmt.Printf("The value of 'foo' is: %s\n", value)
			return nil
		})
	}

	// Output:
	// The value of 'foo' is: bar
}

func ExampleDB_View() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

	// Insert data into a bucket.
	db.Update(func(tx *bolt.Tx) error {
		tx.CreateBucket([]byte("people"))
		b := tx.Bucket([]byte("people"))
		b.Put([]byte("john"), []byte("doe"))
		b.Put([]byte("susy"), []byte("que"))
		return nil
	})

	// Access data from within a read-only transactional block.
	db.View(func(tx *bolt.Tx) error {
		v := tx.Bucket([]byte("people")).Get([]byte("john"))
		fmt.Printf("John's last name is %s.\n", v)
		return nil
	})

	// Output:
	// John's last name is doe.
}

func ExampleDB_Begin_ReadOnly() {
	// Open the database.
	db, _ := bolt.Open(tempfile(), 0666, nil)
	defer os.Remove(db.Path())
	defer db.Close()

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

	// Create several keys in a transaction.
	tx, _ := db.Begin(true)
	b := tx.Bucket([]byte("widgets"))
	b.Put([]byte("john"), []byte("blue"))
	b.Put([]byte("abby"), []byte("red"))
	b.Put([]byte("zephyr"), []byte("purple"))
	tx.Commit()

	// Iterate over the values in sorted key order.
	tx, _ = db.Begin(false)
	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)
	}
	tx.Rollback()

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

// Ensure that a database can be opened without error.
func TestOpen(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)
	db, err := bolt.Open(path, 0666, nil)
	assert(t, db != nil, "")
	ok(t, err)
	equals(t, db.Path(), path)
	ok(t, db.Close())
}

// Ensure that the database returns an error if the file handle cannot be open.
func TestDB_Open_FileError(t *testing.T) {
	path := tempfile()
	defer os.Remove(path)

	_, err := bolt.Open(path+"/youre-not-my-real-parent", 0666, nil)
	assert(t, err.(*os.PathError) != nil, "")
	equals(t, path+"/youre-not-my-real-parent", err.(*os.PathError).Path)
	equals(t, "open", err.(*os.PathError).Op)
}

// open creates and opens a Bolt database in the temp directory.
func open(fn func(*bolt.DB, string)) {
	path := tempfile()
	defer os.RemoveAll(path)

	db, err := bolt.Open(path, 0600, nil)
	if err != nil {
		panic("db open error: " + err.Error())
	}
	fn(db, path)
}

// Ensure that opening an already open database file will timeout.
func TestOpen_Timeout(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Skip("timeout not supported on windows")
	}

	path := tempfile()
	defer os.Remove(path)

	// Open a data file.
	db0, err := bolt.Open(path, 0666, nil)
	assert(t, db0 != nil, "")
	ok(t, err)

	// Attempt to open the database again.
	start := time.Now()
	db1, err := bolt.Open(path, 0666, &bolt.Options{Timeout: 100 * time.Millisecond})
	assert(t, db1 == nil, "")
	equals(t, bolt.ErrTimeout, err)
	assert(t, time.Since(start) > 100*time.Millisecond, "")

	db0.Close()
}