add other session providers (#5963)

vendor/github.com/lunny/nodb/tx.go

@@ -0,0 +1,113 @@
+package nodb
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/lunny/nodb/store"
+)
+
+var (
+	ErrNestTx = errors.New("nest transaction not supported")
+	ErrTxDone = errors.New("Transaction has already been committed or rolled back")
+)
+
+type Tx struct {
+	*DB
+
+	tx *store.Tx
+
+	logs [][]byte
+}
+
+func (db *DB) IsTransaction() bool {
+	return db.status == DBInTransaction
+}
+
+// Begin a transaction, it will block all other write operations before calling Commit or Rollback.
+// You must be very careful to prevent long-time transaction.
+func (db *DB) Begin() (*Tx, error) {
+	if db.IsTransaction() {
+		return nil, ErrNestTx
+	}
+
+	tx := new(Tx)
+
+	tx.DB = new(DB)
+	tx.DB.l = db.l
+
+	tx.l.wLock.Lock()
+
+	tx.DB.sdb = db.sdb
+
+	var err error
+	tx.tx, err = db.sdb.Begin()
+	if err != nil {
+		tx.l.wLock.Unlock()
+		return nil, err
+	}
+
+	tx.DB.bucket = tx.tx
+
+	tx.DB.status = DBInTransaction
+
+	tx.DB.index = db.index
+
+	tx.DB.kvBatch = tx.newBatch()
+	tx.DB.listBatch = tx.newBatch()
+	tx.DB.hashBatch = tx.newBatch()
+	tx.DB.zsetBatch = tx.newBatch()
+	tx.DB.binBatch = tx.newBatch()
+	tx.DB.setBatch = tx.newBatch()
+
+	return tx, nil
+}
+
+func (tx *Tx) Commit() error {
+	if tx.tx == nil {
+		return ErrTxDone
+	}
+
+	tx.l.commitLock.Lock()
+	err := tx.tx.Commit()
+	tx.tx = nil
+
+	if len(tx.logs) > 0 {
+		tx.l.binlog.Log(tx.logs...)
+	}
+
+	tx.l.commitLock.Unlock()
+
+	tx.l.wLock.Unlock()
+
+	tx.DB.bucket = nil
+
+	return err
+}
+
+func (tx *Tx) Rollback() error {
+	if tx.tx == nil {
+		return ErrTxDone
+	}
+
+	err := tx.tx.Rollback()
+	tx.tx = nil
+
+	tx.l.wLock.Unlock()
+	tx.DB.bucket = nil
+
+	return err
+}
+
+func (tx *Tx) newBatch() *batch {
+	return tx.l.newBatch(tx.tx.NewWriteBatch(), &txBatchLocker{}, tx)
+}
+
+func (tx *Tx) Select(index int) error {
+	if index < 0 || index >= int(MaxDBNumber) {
+		return fmt.Errorf("invalid db index %d", index)
+	}
+
+	tx.DB.index = uint8(index)
+	return nil
+}