--- /dev/null
+// Copyright (c) 2012, 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 (
+ "time"
+
+ "github.com/syndtr/goleveldb/leveldb/memdb"
+ "github.com/syndtr/goleveldb/leveldb/opt"
+ "github.com/syndtr/goleveldb/leveldb/util"
+)
+
+func (db *DB) writeJournal(batches []*Batch, seq uint64, sync bool) error {
+ wr, err := db.journal.Next()
+ if err != nil {
+ return err
+ }
+ if err := writeBatchesWithHeader(wr, batches, seq); err != nil {
+ return err
+ }
+ if err := db.journal.Flush(); err != nil {
+ return err
+ }
+ if sync {
+ return db.journalWriter.Sync()
+ }
+ return nil
+}
+
+func (db *DB) rotateMem(n int, wait bool) (mem *memDB, err error) {
+ retryLimit := 3
+retry:
+ // Wait for pending memdb compaction.
+ err = db.compTriggerWait(db.mcompCmdC)
+ if err != nil {
+ return
+ }
+ retryLimit--
+
+ // Create new memdb and journal.
+ mem, err = db.newMem(n)
+ if err != nil {
+ if err == errHasFrozenMem {
+ if retryLimit <= 0 {
+ panic("BUG: still has frozen memdb")
+ }
+ goto retry
+ }
+ return
+ }
+
+ // Schedule memdb compaction.
+ if wait {
+ err = db.compTriggerWait(db.mcompCmdC)
+ } else {
+ db.compTrigger(db.mcompCmdC)
+ }
+ return
+}
+
+func (db *DB) flush(n int) (mdb *memDB, mdbFree int, err error) {
+ delayed := false
+ slowdownTrigger := db.s.o.GetWriteL0SlowdownTrigger()
+ pauseTrigger := db.s.o.GetWriteL0PauseTrigger()
+ flush := func() (retry bool) {
+ mdb = db.getEffectiveMem()
+ if mdb == nil {
+ err = ErrClosed
+ return false
+ }
+ defer func() {
+ if retry {
+ mdb.decref()
+ mdb = nil
+ }
+ }()
+ tLen := db.s.tLen(0)
+ mdbFree = mdb.Free()
+ switch {
+ case tLen >= slowdownTrigger && !delayed:
+ delayed = true
+ time.Sleep(time.Millisecond)
+ case mdbFree >= n:
+ return false
+ case tLen >= pauseTrigger:
+ delayed = true
+ err = db.compTriggerWait(db.tcompCmdC)
+ if err != nil {
+ return false
+ }
+ default:
+ // Allow memdb to grow if it has no entry.
+ if mdb.Len() == 0 {
+ mdbFree = n
+ } else {
+ mdb.decref()
+ mdb, err = db.rotateMem(n, false)
+ if err == nil {
+ mdbFree = mdb.Free()
+ } else {
+ mdbFree = 0
+ }
+ }
+ return false
+ }
+ return true
+ }
+ start := time.Now()
+ for flush() {
+ }
+ if delayed {
+ db.writeDelay += time.Since(start)
+ db.writeDelayN++
+ } else if db.writeDelayN > 0 {
+ db.logf("db@write was delayed N·%d T·%v", db.writeDelayN, db.writeDelay)
+ db.writeDelay = 0
+ db.writeDelayN = 0
+ }
+ return
+}
+
+type writeMerge struct {
+ sync bool
+ batch *Batch
+ keyType keyType
+ key, value []byte
+}
+
+func (db *DB) unlockWrite(overflow bool, merged int, err error) {
+ for i := 0; i < merged; i++ {
+ db.writeAckC <- err
+ }
+ if overflow {
+ // Pass lock to the next write (that failed to merge).
+ db.writeMergedC <- false
+ } else {
+ // Release lock.
+ <-db.writeLockC
+ }
+}
+
+// ourBatch if defined should equal with batch.
+func (db *DB) writeLocked(batch, ourBatch *Batch, merge, sync bool) error {
+ // Try to flush memdb. This method would also trying to throttle writes
+ // if it is too fast and compaction cannot catch-up.
+ mdb, mdbFree, err := db.flush(batch.internalLen)
+ if err != nil {
+ db.unlockWrite(false, 0, err)
+ return err
+ }
+ defer mdb.decref()
+
+ var (
+ overflow bool
+ merged int
+ batches = []*Batch{batch}
+ )
+
+ if merge {
+ // Merge limit.
+ var mergeLimit int
+ if batch.internalLen > 128<<10 {
+ mergeLimit = (1 << 20) - batch.internalLen
+ } else {
+ mergeLimit = 128 << 10
+ }
+ mergeCap := mdbFree - batch.internalLen
+ if mergeLimit > mergeCap {
+ mergeLimit = mergeCap
+ }
+
+ merge:
+ for mergeLimit > 0 {
+ select {
+ case incoming := <-db.writeMergeC:
+ if incoming.batch != nil {
+ // Merge batch.
+ if incoming.batch.internalLen > mergeLimit {
+ overflow = true
+ break merge
+ }
+ batches = append(batches, incoming.batch)
+ mergeLimit -= incoming.batch.internalLen
+ } else {
+ // Merge put.
+ internalLen := len(incoming.key) + len(incoming.value) + 8
+ if internalLen > mergeLimit {
+ overflow = true
+ break merge
+ }
+ if ourBatch == nil {
+ ourBatch = db.batchPool.Get().(*Batch)
+ ourBatch.Reset()
+ batches = append(batches, ourBatch)
+ }
+ // We can use same batch since concurrent write doesn't
+ // guarantee write order.
+ ourBatch.appendRec(incoming.keyType, incoming.key, incoming.value)
+ mergeLimit -= internalLen
+ }
+ sync = sync || incoming.sync
+ merged++
+ db.writeMergedC <- true
+
+ default:
+ break merge
+ }
+ }
+ }
+
+ // Seq number.
+ seq := db.seq + 1
+
+ // Write journal.
+ if err := db.writeJournal(batches, seq, sync); err != nil {
+ db.unlockWrite(overflow, merged, err)
+ return err
+ }
+
+ // Put batches.
+ for _, batch := range batches {
+ if err := batch.putMem(seq, mdb.DB); err != nil {
+ panic(err)
+ }
+ seq += uint64(batch.Len())
+ }
+
+ // Incr seq number.
+ db.addSeq(uint64(batchesLen(batches)))
+
+ // Rotate memdb if it's reach the threshold.
+ if batch.internalLen >= mdbFree {
+ db.rotateMem(0, false)
+ }
+
+ db.unlockWrite(overflow, merged, nil)
+ return nil
+}
+
+// Write apply the given batch to the DB. The batch records will be applied
+// sequentially. Write might be used concurrently, when used concurrently and
+// batch is small enough, write will try to merge the batches. Set NoWriteMerge
+// option to true to disable write merge.
+//
+// It is safe to modify the contents of the arguments after Write returns but
+// not before. Write will not modify content of the batch.
+func (db *DB) Write(batch *Batch, wo *opt.WriteOptions) error {
+ if err := db.ok(); err != nil || batch == nil || batch.Len() == 0 {
+ return err
+ }
+
+ // If the batch size is larger than write buffer, it may justified to write
+ // using transaction instead. Using transaction the batch will be written
+ // into tables directly, skipping the journaling.
+ if batch.internalLen > db.s.o.GetWriteBuffer() && !db.s.o.GetDisableLargeBatchTransaction() {
+ tr, err := db.OpenTransaction()
+ if err != nil {
+ return err
+ }
+ if err := tr.Write(batch, wo); err != nil {
+ tr.Discard()
+ return err
+ }
+ return tr.Commit()
+ }
+
+ merge := !wo.GetNoWriteMerge() && !db.s.o.GetNoWriteMerge()
+ sync := wo.GetSync() && !db.s.o.GetNoSync()
+
+ // Acquire write lock.
+ if merge {
+ select {
+ case db.writeMergeC <- writeMerge{sync: sync, batch: batch}:
+ if <-db.writeMergedC {
+ // Write is merged.
+ return <-db.writeAckC
+ }
+ // Write is not merged, the write lock is handed to us. Continue.
+ case db.writeLockC <- struct{}{}:
+ // Write lock acquired.
+ case err := <-db.compPerErrC:
+ // Compaction error.
+ return err
+ case <-db.closeC:
+ // Closed
+ return ErrClosed
+ }
+ } else {
+ select {
+ case db.writeLockC <- struct{}{}:
+ // Write lock acquired.
+ case err := <-db.compPerErrC:
+ // Compaction error.
+ return err
+ case <-db.closeC:
+ // Closed
+ return ErrClosed
+ }
+ }
+
+ return db.writeLocked(batch, nil, merge, sync)
+}
+
+func (db *DB) putRec(kt keyType, key, value []byte, wo *opt.WriteOptions) error {
+ if err := db.ok(); err != nil {
+ return err
+ }
+
+ merge := !wo.GetNoWriteMerge() && !db.s.o.GetNoWriteMerge()
+ sync := wo.GetSync() && !db.s.o.GetNoSync()
+
+ // Acquire write lock.
+ if merge {
+ select {
+ case db.writeMergeC <- writeMerge{sync: sync, keyType: kt, key: key, value: value}:
+ if <-db.writeMergedC {
+ // Write is merged.
+ return <-db.writeAckC
+ }
+ // Write is not merged, the write lock is handed to us. Continue.
+ case db.writeLockC <- struct{}{}:
+ // Write lock acquired.
+ case err := <-db.compPerErrC:
+ // Compaction error.
+ return err
+ case <-db.closeC:
+ // Closed
+ return ErrClosed
+ }
+ } else {
+ select {
+ case db.writeLockC <- struct{}{}:
+ // Write lock acquired.
+ case err := <-db.compPerErrC:
+ // Compaction error.
+ return err
+ case <-db.closeC:
+ // Closed
+ return ErrClosed
+ }
+ }
+
+ batch := db.batchPool.Get().(*Batch)
+ batch.Reset()
+ batch.appendRec(kt, key, value)
+ return db.writeLocked(batch, batch, merge, sync)
+}
+
+// Put sets the value for the given key. It overwrites any previous value
+// for that key; a DB is not a multi-map. Write merge also applies for Put, see
+// Write.
+//
+// It is safe to modify the contents of the arguments after Put returns but not
+// before.
+func (db *DB) Put(key, value []byte, wo *opt.WriteOptions) error {
+ return db.putRec(keyTypeVal, key, value, wo)
+}
+
+// Delete deletes the value for the given key. Delete will not returns error if
+// key doesn't exist. Write merge also applies for Delete, see Write.
+//
+// It is safe to modify the contents of the arguments after Delete returns but
+// not before.
+func (db *DB) Delete(key []byte, wo *opt.WriteOptions) error {
+ return db.putRec(keyTypeDel, key, nil, wo)
+}
+
+func isMemOverlaps(icmp *iComparer, mem *memdb.DB, min, max []byte) bool {
+ iter := mem.NewIterator(nil)
+ defer iter.Release()
+ return (max == nil || (iter.First() && icmp.uCompare(max, internalKey(iter.Key()).ukey()) >= 0)) &&
+ (min == nil || (iter.Last() && icmp.uCompare(min, internalKey(iter.Key()).ukey()) <= 0))
+}
+
+// CompactRange compacts the underlying DB for the given key range.
+// In particular, deleted and overwritten versions are discarded,
+// and the data is rearranged to reduce the cost of operations
+// needed to access the data. This operation should typically only
+// be invoked by users who understand the underlying implementation.
+//
+// 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.
+// Therefore if both is nil then it will compact entire DB.
+func (db *DB) CompactRange(r util.Range) error {
+ if err := db.ok(); err != nil {
+ return err
+ }
+
+ // Lock writer.
+ select {
+ case db.writeLockC <- struct{}{}:
+ case err := <-db.compPerErrC:
+ return err
+ case <-db.closeC:
+ return ErrClosed
+ }
+
+ // Check for overlaps in memdb.
+ mdb := db.getEffectiveMem()
+ if mdb == nil {
+ return ErrClosed
+ }
+ defer mdb.decref()
+ if isMemOverlaps(db.s.icmp, mdb.DB, r.Start, r.Limit) {
+ // Memdb compaction.
+ if _, err := db.rotateMem(0, false); err != nil {
+ <-db.writeLockC
+ return err
+ }
+ <-db.writeLockC
+ if err := db.compTriggerWait(db.mcompCmdC); err != nil {
+ return err
+ }
+ } else {
+ <-db.writeLockC
+ }
+
+ // Table compaction.
+ return db.compTriggerRange(db.tcompCmdC, -1, r.Start, r.Limit)
+}
+
+// SetReadOnly makes DB read-only. It will stay read-only until reopened.
+func (db *DB) SetReadOnly() error {
+ if err := db.ok(); err != nil {
+ return err
+ }
+
+ // Lock writer.
+ select {
+ case db.writeLockC <- struct{}{}:
+ db.compWriteLocking = true
+ case err := <-db.compPerErrC:
+ return err
+ case <-db.closeC:
+ return ErrClosed
+ }
+
+ // Set compaction read-only.
+ select {
+ case db.compErrSetC <- ErrReadOnly:
+ case perr := <-db.compPerErrC:
+ return perr
+ case <-db.closeC:
+ return ErrClosed
+ }
+
+ return nil
+}
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