transaction.go

/*
 * Copyright [2023] [studyzy(studyzy@gmail.com)]
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package shardingdb

import (
	"errors"

	"github.com/syndtr/goleveldb/leveldb"
	"github.com/syndtr/goleveldb/leveldb/comparer"
	"github.com/syndtr/goleveldb/leveldb/iterator"
	"github.com/syndtr/goleveldb/leveldb/opt"
	"github.com/syndtr/goleveldb/leveldb/util"
)

// ShardingTransaction is a transaction of multiple db
type ShardingTransaction struct {
	txHandles    []Transaction
	length       uint16
	shardingFunc ShardingFunc
	//lock         *sync.RWMutex
	encryptor Encryptor
}

// Get returns the value for the given key
func (s ShardingTransaction) Get(key []byte, ro *opt.ReadOptions) ([]byte, error) {
	dbIndex := s.shardingFunc(key, s.length)
	val, err := s.txHandles[dbIndex].Get(key, ro)
	if err != nil {
		return nil, err
	}
	if s.encryptor != nil && len(val) > 0 {
		val, err = s.encryptor.Decrypt(val)
		if err != nil {
			return nil, err
		}
	}
	return val, nil
}

// Has returns whether the DB does contains the given key
func (s ShardingTransaction) Has(key []byte, ro *opt.ReadOptions) (bool, error) {
	dbIndex := s.shardingFunc(key, s.length)
	return s.txHandles[dbIndex].Has(key, ro)
}

// NewIterator returns an iterator for the latest snapshot of the DB.
func (s ShardingTransaction) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
	iters := make([]iterator.Iterator, s.length)
	for idx, dbHandle := range s.txHandles {
		iters[idx] = dbHandle.NewIterator(slice, ro)
	}
	miter := iterator.NewMergedIterator(iters, comparer.DefaultComparer, true)
	if s.encryptor != nil {
		return &encryptIterator{iter: miter, encryptor: s.encryptor}
	}
	return miter
}

// Put sets the value for the given key.
func (s ShardingTransaction) Put(key, value []byte, wo *opt.WriteOptions) error {
	dbIndex := s.shardingFunc(key, s.length)

	if s.encryptor != nil && len(value) > 0 {
		evalue, err := s.encryptor.Encrypt(value)
		if err != nil {
			return err
		}
		return s.txHandles[dbIndex].Put(key, evalue, wo)
	}
	return s.txHandles[dbIndex].Put(key, value, wo)
}

// Delete deletes the value for the given key.
func (s ShardingTransaction) Delete(key []byte, wo *opt.WriteOptions) error {
	dbIndex := s.shardingFunc(key, s.length)
	return s.txHandles[dbIndex].Delete(key, wo)
}

// Write writes the given batch to the DB.
func (s ShardingTransaction) Write(b *leveldb.Batch, wo *opt.WriteOptions) error {
	//Split batch into multiple batches
	batches, err := splitBatch(b, s.length, s.shardingFunc, s.encryptor)
	if err != nil {
		return err
	}
	//Write batches to different txHandles
	for idx, b1 := range batches {
		if err := s.txHandles[idx].Write(b1, wo); err != nil {
			return err
		}
	}
	return nil
}

// Commit commits the transaction.
func (s ShardingTransaction) Commit() error {
	//defer s.lock.Unlock()
	if len(s.txHandles) == 0 {
		return errors.New("no transaction to commit")
	}
	for _, dbHandle := range s.txHandles {
		err := dbHandle.Commit()
		if err != nil {
			return err
		}
	}
	return nil
}

// Discard discards the transaction.
func (s ShardingTransaction) Discard() {
	//defer s.lock.Unlock()
	for _, dbHandle := range s.txHandles {
		dbHandle.Discard()
	}
}

var _ Transaction = (*ShardingTransaction)(nil)