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session.go
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session.go
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// 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 (
"errors"
"io"
"os"
"sync"
"sync/atomic"
"github.com/philsong/goleveldb/leveldb/iterator"
"github.com/philsong/goleveldb/leveldb/journal"
"github.com/philsong/goleveldb/leveldb/opt"
"github.com/philsong/goleveldb/leveldb/storage"
"github.com/philsong/goleveldb/leveldb/util"
)
// ErrManifest is the type that wraps errors produced by missing
// or corrupted manifest file.
type ErrManifest struct {
Err error
}
func (e ErrManifest) Error() string {
return e.Err.Error()
}
// session represent a persistent database session.
type session struct {
// Need 64-bit alignment.
stFileNum uint64 // current unused file number
stJournalNum uint64 // current journal file number; need external synchronization
stPrevJournalNum uint64 // prev journal file number; no longer used; for compatibility with older version of leveldb
stSeq uint64 // last mem compacted seq; need external synchronization
stor storage.Storage
storLock util.Releaser
o *opt.Options
cmp *iComparer
tops *tOps
manifest *journal.Writer
manifestWriter storage.Writer
manifestFile storage.File
stCPtrs [kNumLevels]iKey // compact pointers; need external synchronization
stVersion *version // current version
vmu sync.Mutex
}
func newSession(stor storage.Storage, o *opt.Options) (s *session, err error) {
if stor == nil {
return nil, os.ErrInvalid
}
storLock, err := stor.Lock()
if err != nil {
return
}
s = &session{
stor: stor,
storLock: storLock,
}
s.setOptions(o)
s.tops = newTableOps(s, s.o.GetMaxOpenFiles())
s.setVersion(&version{s: s})
return
}
// Close session.
func (s *session) close() {
s.tops.close()
if bc := s.o.GetBlockCache(); bc != nil {
bc.Purge(nil)
}
if s.manifest != nil {
s.manifest.Close()
}
if s.manifestWriter != nil {
s.manifestWriter.Close()
}
}
func (s *session) release() {
s.storLock.Release()
}
// Create a new database session; need external synchronization.
func (s *session) create() error {
// create manifest
return s.newManifest(nil, nil)
}
// Recover a database session; need external synchronization.
func (s *session) recover() (err error) {
defer func() {
if os.IsNotExist(err) {
// Don't return os.ErrNotExist if the underlying storage contains
// other files that belong to LevelDB. So the DB won't get trashed.
if files, _ := s.stor.GetFiles(storage.TypeAll); len(files) > 0 {
err = ErrManifest{Err: errors.New("leveldb: manifest file missing")}
}
}
}()
file, err := s.stor.GetManifest()
if err != nil {
return
}
reader, err := file.Open()
if err != nil {
return
}
defer reader.Close()
strict := s.o.GetStrict(opt.StrictManifest)
jr := journal.NewReader(reader, dropper{s, file}, strict, true)
staging := s.version_NB().newStaging()
rec := &sessionRecord{}
for {
var r io.Reader
r, err = jr.Next()
if err != nil {
if err == io.EOF {
err = nil
break
}
return
}
err = rec.decode(r)
if err == nil {
// save compact pointers
for _, rp := range rec.compactionPointers {
s.stCPtrs[rp.level] = iKey(rp.key)
}
// commit record to version staging
staging.commit(rec)
} else if strict {
return ErrManifest{Err: err}
} else {
s.logf("manifest error: %v (skipped)", err)
}
rec.resetCompactionPointers()
rec.resetAddedTables()
rec.resetDeletedTables()
}
switch {
case !rec.has(recComparer):
return ErrManifest{Err: errors.New("leveldb: manifest missing comparer name")}
case rec.comparer != s.cmp.cmp.Name():
return ErrManifest{Err: errors.New("leveldb: comparer mismatch, " + "want '" + s.cmp.cmp.Name() + "', " + "got '" + rec.comparer + "'")}
case !rec.has(recNextNum):
return ErrManifest{Err: errors.New("leveldb: manifest missing next file number")}
case !rec.has(recJournalNum):
return ErrManifest{Err: errors.New("leveldb: manifest missing journal file number")}
case !rec.has(recSeq):
return ErrManifest{Err: errors.New("leveldb: manifest missing seq number")}
}
s.manifestFile = file
s.setVersion(staging.finish())
s.setFileNum(rec.nextNum)
s.recordCommited(rec)
return nil
}
// Commit session; need external synchronization.
func (s *session) commit(r *sessionRecord) (err error) {
// spawn new version based on current version
nv := s.version_NB().spawn(r)
if s.manifest == nil {
// manifest journal writer not yet created, create one
err = s.newManifest(r, nv)
} else {
err = s.flushManifest(r)
}
// finally, apply new version if no error rise
if err == nil {
s.setVersion(nv)
}
return
}
// Pick a compaction based on current state; need external synchronization.
func (s *session) pickCompaction() *compaction {
icmp := s.cmp
ucmp := icmp.cmp
v := s.version_NB()
var level int
var t0 tFiles
if v.cScore >= 1 {
level = v.cLevel
cp := s.stCPtrs[level]
tt := v.tables[level]
for _, t := range tt {
if cp == nil || icmp.Compare(t.max, cp) > 0 {
t0 = append(t0, t)
break
}
}
if len(t0) == 0 {
t0 = append(t0, tt[0])
}
} else {
if p := atomic.LoadPointer(&v.cSeek); p != nil {
ts := (*tSet)(p)
level = ts.level
t0 = append(t0, ts.table)
} else {
return nil
}
}
c := &compaction{s: s, version: v, level: level}
if level == 0 {
min, max := t0.getRange(icmp)
t0 = nil
v.tables[0].getOverlaps(min.ukey(), max.ukey(), &t0, false, ucmp)
}
c.tables[0] = t0
c.expand()
return c
}
// Create compaction from given level and range; need external synchronization.
func (s *session) getCompactionRange(level int, min, max []byte) *compaction {
v := s.version_NB()
var t0 tFiles
v.tables[level].getOverlaps(min, max, &t0, level != 0, s.cmp.cmp)
if len(t0) == 0 {
return nil
}
c := &compaction{s: s, version: v, level: level}
c.tables[0] = t0
c.expand()
return c
}
// compaction represent a compaction state
type compaction struct {
s *session
version *version
level int
tables [2]tFiles
gp tFiles
gpidx int
seenKey bool
overlappedBytes uint64
min, max iKey
tPtrs [kNumLevels]int
}
// Expand compacted tables; need external synchronization.
func (c *compaction) expand() {
s := c.s
v := c.version
icmp := s.cmp
ucmp := icmp.cmp
level := c.level
vt0, vt1 := v.tables[level], v.tables[level+1]
t0, t1 := c.tables[0], c.tables[1]
min, max := t0.getRange(icmp)
vt1.getOverlaps(min.ukey(), max.ukey(), &t1, true, ucmp)
// Get entire range covered by compaction
amin, amax := append(t0, t1...).getRange(icmp)
// See if we can grow the number of inputs in "level" without
// changing the number of "level+1" files we pick up.
if len(t1) > 0 {
var exp0 tFiles
vt0.getOverlaps(amin.ukey(), amax.ukey(), &exp0, level != 0, ucmp)
if len(exp0) > len(t0) && t1.size()+exp0.size() < kExpCompactionMaxBytes {
var exp1 tFiles
xmin, xmax := exp0.getRange(icmp)
vt1.getOverlaps(xmin.ukey(), xmax.ukey(), &exp1, true, ucmp)
if len(exp1) == len(t1) {
s.logf("table@compaction expanding L%d+L%d (F·%d S·%s)+(F·%d S·%s) -> (F·%d S·%s)+(F·%d S·%s)",
level, level+1, len(t0), shortenb(int(t0.size())), len(t1), shortenb(int(t1.size())),
len(exp0), shortenb(int(exp0.size())), len(exp1), shortenb(int(exp1.size())))
min, max = xmin, xmax
t0, t1 = exp0, exp1
amin, amax = append(t0, t1...).getRange(icmp)
}
}
}
// Compute the set of grandparent files that overlap this compaction
// (parent == level+1; grandparent == level+2)
if level+2 < kNumLevels {
v.tables[level+2].getOverlaps(amin.ukey(), amax.ukey(), &c.gp, true, ucmp)
}
c.tables[0], c.tables[1] = t0, t1
c.min, c.max = min, max
}
// Check whether compaction is trivial.
func (c *compaction) trivial() bool {
return len(c.tables[0]) == 1 && len(c.tables[1]) == 0 && c.gp.size() <= kMaxGrandParentOverlapBytes
}
func (c *compaction) isBaseLevelForKey(key []byte) bool {
s := c.s
v := c.version
ucmp := s.cmp.cmp
for level, tt := range v.tables[c.level+2:] {
for c.tPtrs[level] < len(tt) {
t := tt[c.tPtrs[level]]
if ucmp.Compare(key, t.max.ukey()) <= 0 {
// We've advanced far enough
if ucmp.Compare(key, t.min.ukey()) >= 0 {
// Key falls in this file's range, so definitely not base level
return false
}
break
}
c.tPtrs[level]++
}
}
return true
}
func (c *compaction) shouldStopBefore(key iKey) bool {
icmp := c.s.cmp
for ; c.gpidx < len(c.gp); c.gpidx++ {
gp := c.gp[c.gpidx]
if icmp.Compare(key, gp.max) <= 0 {
break
}
if c.seenKey {
c.overlappedBytes += gp.size
}
}
c.seenKey = true
if c.overlappedBytes > kMaxGrandParentOverlapBytes {
// Too much overlap for current output; start new output
c.overlappedBytes = 0
return true
}
return false
}
func (c *compaction) newIterator() iterator.Iterator {
s := c.s
icmp := s.cmp
level := c.level
icap := 2
if c.level == 0 {
icap = len(c.tables[0]) + 1
}
its := make([]iterator.Iterator, 0, icap)
ro := &opt.ReadOptions{
DontFillCache: true,
}
strict := s.o.GetStrict(opt.StrictIterator)
for i, tt := range c.tables {
if len(tt) == 0 {
continue
}
if level+i == 0 {
for _, t := range tt {
its = append(its, s.tops.newIterator(t, nil, ro))
}
} else {
it := iterator.NewIndexedIterator(tt.newIndexIterator(s.tops, icmp, nil, ro), strict, true)
its = append(its, it)
}
}
return iterator.NewMergedIterator(its, icmp, true)
}