Method beginTx

db.go:792–837

()

}

func (db *DB) beginTx() (*Tx, error) {
	// Lock the meta pages while we initialize the transaction. We obtain
	// the meta lock before the mmap lock because that's the order that the
	// write transaction will obtain them.
	db.metalock.Lock()

	// Obtain a read-only lock on the mmap. When the mmap is remapped it will
	// obtain a write lock so all transactions must finish before it can be
	// remapped.
	db.mmaplock.RLock()

	// Exit if the database is not open yet.
	if !db.opened {
		db.mmaplock.RUnlock()
		db.metalock.Unlock()
		return nil, berrors.ErrDatabaseNotOpen
	}

	// Exit if the database is not correctly mapped.
	if db.data == nil {
		db.mmaplock.RUnlock()
		db.metalock.Unlock()
		return nil, berrors.ErrInvalidMapping
	}

	// Create a transaction associated with the database.
	t := &Tx{}
	t.init(db)

	if db.freelist != nil {
		db.freelist.AddReadonlyTXID(t.meta.Txid())
	}

	// Unlock the meta pages.
	db.metalock.Unlock()

	// Update the transaction stats.
	if db.stats != nil {
		db.statlock.Lock()
		db.stats.TxN++
		db.stats.OpenTxN++
		db.statlock.Unlock()
	}

	return t, nil
}

func (db *DB) beginRWTx() (*Tx, error) {
	// If the database was opened with Options.ReadOnly, return an error.