--- /dev/null
+// Copyright (c) 2016, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+ "errors"
+ "sync"
+ "time"
+
+ "github.com/syndtr/goleveldb/leveldb/iterator"
+ "github.com/syndtr/goleveldb/leveldb/opt"
+ "github.com/syndtr/goleveldb/leveldb/util"
+)
+
+var errTransactionDone = errors.New("leveldb: transaction already closed")
+
+// Transaction is the transaction handle.
+type Transaction struct {
+ db *DB
+ lk sync.RWMutex
+ seq uint64
+ mem *memDB
+ tables tFiles
+ ikScratch []byte
+ rec sessionRecord
+ stats cStatStaging
+ closed bool
+}
+
+// Get gets the value for the given key. It returns ErrNotFound if the
+// DB does not contains the key.
+//
+// The returned slice is its own copy, it is safe to modify the contents
+// of the returned slice.
+// It is safe to modify the contents of the argument after Get returns.
+func (tr *Transaction) Get(key []byte, ro *opt.ReadOptions) ([]byte, error) {
+ tr.lk.RLock()
+ defer tr.lk.RUnlock()
+ if tr.closed {
+ return nil, errTransactionDone
+ }
+ return tr.db.get(tr.mem.DB, tr.tables, key, tr.seq, ro)
+}
+
+// Has returns true if the DB does contains the given key.
+//
+// It is safe to modify the contents of the argument after Has returns.
+func (tr *Transaction) Has(key []byte, ro *opt.ReadOptions) (bool, error) {
+ tr.lk.RLock()
+ defer tr.lk.RUnlock()
+ if tr.closed {
+ return false, errTransactionDone
+ }
+ return tr.db.has(tr.mem.DB, tr.tables, key, tr.seq, ro)
+}
+
+// NewIterator returns an iterator for the latest snapshot of the transaction.
+// The returned iterator is not safe for concurrent use, but it is safe to use
+// multiple iterators concurrently, with each in a dedicated goroutine.
+// It is also safe to use an iterator concurrently while writes to the
+// transaction. The resultant key/value pairs are guaranteed to be consistent.
+//
+// Slice allows slicing the iterator to only contains keys in the given
+// range. A nil Range.Start is treated as a key before all keys in the
+// DB. And a nil Range.Limit is treated as a key after all keys in
+// the DB.
+//
+// The iterator must be released after use, by calling Release method.
+//
+// Also read Iterator documentation of the leveldb/iterator package.
+func (tr *Transaction) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+ tr.lk.RLock()
+ defer tr.lk.RUnlock()
+ if tr.closed {
+ return iterator.NewEmptyIterator(errTransactionDone)
+ }
+ tr.mem.incref()
+ return tr.db.newIterator(tr.mem, tr.tables, tr.seq, slice, ro)
+}
+
+func (tr *Transaction) flush() error {
+ // Flush memdb.
+ if tr.mem.Len() != 0 {
+ tr.stats.startTimer()
+ iter := tr.mem.NewIterator(nil)
+ t, n, err := tr.db.s.tops.createFrom(iter)
+ iter.Release()
+ tr.stats.stopTimer()
+ if err != nil {
+ return err
+ }
+ if tr.mem.getref() == 1 {
+ tr.mem.Reset()
+ } else {
+ tr.mem.decref()
+ tr.mem = tr.db.mpoolGet(0)
+ tr.mem.incref()
+ }
+ tr.tables = append(tr.tables, t)
+ tr.rec.addTableFile(0, t)
+ tr.stats.write += t.size
+ tr.db.logf("transaction@flush created L0@%d N·%d S·%s %q:%q", t.fd.Num, n, shortenb(int(t.size)), t.imin, t.imax)
+ }
+ return nil
+}
+
+func (tr *Transaction) put(kt keyType, key, value []byte) error {
+ tr.ikScratch = makeInternalKey(tr.ikScratch, key, tr.seq+1, kt)
+ if tr.mem.Free() < len(tr.ikScratch)+len(value) {
+ if err := tr.flush(); err != nil {
+ return err
+ }
+ }
+ if err := tr.mem.Put(tr.ikScratch, value); err != nil {
+ return err
+ }
+ tr.seq++
+ return nil
+}
+
+// Put sets the value for the given key. It overwrites any previous value
+// for that key; a DB is not a multi-map.
+// Please note that the transaction is not compacted until committed, so if you
+// writes 10 same keys, then those 10 same keys are in the transaction.
+//
+// It is safe to modify the contents of the arguments after Put returns.
+func (tr *Transaction) Put(key, value []byte, wo *opt.WriteOptions) error {
+ tr.lk.Lock()
+ defer tr.lk.Unlock()
+ if tr.closed {
+ return errTransactionDone
+ }
+ return tr.put(keyTypeVal, key, value)
+}
+
+// Delete deletes the value for the given key.
+// Please note that the transaction is not compacted until committed, so if you
+// writes 10 same keys, then those 10 same keys are in the transaction.
+//
+// It is safe to modify the contents of the arguments after Delete returns.
+func (tr *Transaction) Delete(key []byte, wo *opt.WriteOptions) error {
+ tr.lk.Lock()
+ defer tr.lk.Unlock()
+ if tr.closed {
+ return errTransactionDone
+ }
+ return tr.put(keyTypeDel, key, nil)
+}
+
+// Write apply the given batch to the transaction. The batch will be applied
+// sequentially.
+// Please note that the transaction is not compacted until committed, so if you
+// writes 10 same keys, then those 10 same keys are in the transaction.
+//
+// It is safe to modify the contents of the arguments after Write returns.
+func (tr *Transaction) Write(b *Batch, wo *opt.WriteOptions) error {
+ if b == nil || b.Len() == 0 {
+ return nil
+ }
+
+ tr.lk.Lock()
+ defer tr.lk.Unlock()
+ if tr.closed {
+ return errTransactionDone
+ }
+ return b.replayInternal(func(i int, kt keyType, k, v []byte) error {
+ return tr.put(kt, k, v)
+ })
+}
+
+func (tr *Transaction) setDone() {
+ tr.closed = true
+ tr.db.tr = nil
+ tr.mem.decref()
+ <-tr.db.writeLockC
+}
+
+// Commit commits the transaction. If error is not nil, then the transaction is
+// not committed, it can then either be retried or discarded.
+//
+// Other methods should not be called after transaction has been committed.
+func (tr *Transaction) Commit() error {
+ if err := tr.db.ok(); err != nil {
+ return err
+ }
+
+ tr.lk.Lock()
+ defer tr.lk.Unlock()
+ if tr.closed {
+ return errTransactionDone
+ }
+ if err := tr.flush(); err != nil {
+ // Return error, lets user decide either to retry or discard
+ // transaction.
+ return err
+ }
+ if len(tr.tables) != 0 {
+ // Committing transaction.
+ tr.rec.setSeqNum(tr.seq)
+ tr.db.compCommitLk.Lock()
+ tr.stats.startTimer()
+ var cerr error
+ for retry := 0; retry < 3; retry++ {
+ cerr = tr.db.s.commit(&tr.rec)
+ if cerr != nil {
+ tr.db.logf("transaction@commit error R·%d %q", retry, cerr)
+ select {
+ case <-time.After(time.Second):
+ case <-tr.db.closeC:
+ tr.db.logf("transaction@commit exiting")
+ tr.db.compCommitLk.Unlock()
+ return cerr
+ }
+ } else {
+ // Success. Set db.seq.
+ tr.db.setSeq(tr.seq)
+ break
+ }
+ }
+ tr.stats.stopTimer()
+ if cerr != nil {
+ // Return error, lets user decide either to retry or discard
+ // transaction.
+ return cerr
+ }
+
+ // Update compaction stats. This is safe as long as we hold compCommitLk.
+ tr.db.compStats.addStat(0, &tr.stats)
+
+ // Trigger table auto-compaction.
+ tr.db.compTrigger(tr.db.tcompCmdC)
+ tr.db.compCommitLk.Unlock()
+
+ // Additionally, wait compaction when certain threshold reached.
+ // Ignore error, returns error only if transaction can't be committed.
+ tr.db.waitCompaction()
+ }
+ // Only mark as done if transaction committed successfully.
+ tr.setDone()
+ return nil
+}
+
+func (tr *Transaction) discard() {
+ // Discard transaction.
+ for _, t := range tr.tables {
+ tr.db.logf("transaction@discard @%d", t.fd.Num)
+ if err1 := tr.db.s.stor.Remove(t.fd); err1 == nil {
+ tr.db.s.reuseFileNum(t.fd.Num)
+ }
+ }
+}
+
+// Discard discards the transaction.
+//
+// Other methods should not be called after transaction has been discarded.
+func (tr *Transaction) Discard() {
+ tr.lk.Lock()
+ if !tr.closed {
+ tr.discard()
+ tr.setDone()
+ }
+ tr.lk.Unlock()
+}
+
+func (db *DB) waitCompaction() error {
+ if db.s.tLen(0) >= db.s.o.GetWriteL0PauseTrigger() {
+ return db.compTriggerWait(db.tcompCmdC)
+ }
+ return nil
+}
+
+// OpenTransaction opens an atomic DB transaction. Only one transaction can be
+// opened at a time. Subsequent call to Write and OpenTransaction will be blocked
+// until in-flight transaction is committed or discarded.
+// The returned transaction handle is safe for concurrent use.
+//
+// Transaction is expensive and can overwhelm compaction, especially if
+// transaction size is small. Use with caution.
+//
+// The transaction must be closed once done, either by committing or discarding
+// the transaction.
+// Closing the DB will discard open transaction.
+func (db *DB) OpenTransaction() (*Transaction, error) {
+ if err := db.ok(); err != nil {
+ return nil, err
+ }
+
+ // The write happen synchronously.
+ select {
+ case db.writeLockC <- struct{}{}:
+ case err := <-db.compPerErrC:
+ return nil, err
+ case <-db.closeC:
+ return nil, ErrClosed
+ }
+
+ if db.tr != nil {
+ panic("leveldb: has open transaction")
+ }
+
+ // Flush current memdb.
+ if db.mem != nil && db.mem.Len() != 0 {
+ if _, err := db.rotateMem(0, true); err != nil {
+ return nil, err
+ }
+ }
+
+ // Wait compaction when certain threshold reached.
+ if err := db.waitCompaction(); err != nil {
+ return nil, err
+ }
+
+ tr := &Transaction{
+ db: db,
+ seq: db.seq,
+ mem: db.mpoolGet(0),
+ }
+ tr.mem.incref()
+ db.tr = tr
+ return tr, nil
+}
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