// replayLogFile replays the edits in the named log file.
//
// d.mu must be held when calling this, but the mutex may be dropped and
// re-acquired during the course of this method.
func (d *DB) replayLogFile(ve *versionEdit, fs db.FileSystem, filename string) (maxSeqNum uint64, err error) {
file, err := fs.Open(filename)
if err != nil {
return 0, err
}
defer file.Close()
var (
mem *memdb.MemDB
batchBuf = new(bytes.Buffer)
ikey = make(internalKey, 512)
rr = record.NewReader(file)
)
for {
r, err := rr.Next()
if err == io.EOF {
break
}
if err != nil {
return 0, err
}
_, err = io.Copy(batchBuf, r)
if err != nil {
return 0, err
}
if batchBuf.Len() < batchHeaderLen {
return 0, fmt.Errorf("leveldb: corrupt log file %q", filename)
}
b := Batch{batchBuf.Bytes()}
seqNum := b.seqNum()
seqNum1 := seqNum + uint64(b.count())
if maxSeqNum < seqNum1 {
maxSeqNum = seqNum1
}
if mem == nil {
mem = memdb.New(&d.icmpOpts)
}
t := b.iter()
for ; seqNum != seqNum1; seqNum++ {
kind, ukey, value, ok := t.next()
if !ok {
return 0, fmt.Errorf("leveldb: corrupt log file %q", filename)
}
// Convert seqNum, kind and key into an internalKey, and add that ikey/value
// pair to mem.
//
// TODO: instead of copying to an intermediate buffer (ikey), is it worth
// adding a SetTwoPartKey(db.TwoPartKey{key0, key1}, value, opts) method to
// memdb.MemDB? What effect does that have on the db.Comparer interface?
//
// The C++ LevelDB code does not need an intermediate copy because its memdb
// implementation is a private implementation detail, and copies each internal
// key component from the Batch format straight to the skiplist buffer.
//
// Go's LevelDB considers the memdb functionality to be useful in its own
// right, and so leveldb/memdb is a separate package that is usable without
// having to import the top-level leveldb package. That extra abstraction
// means that we need to copy to an intermediate buffer here, to reconstruct
// the complete internal key to pass to the memdb.
ikey = makeInternalKey(ikey, ukey, kind, seqNum)
mem.Set(ikey, value, nil)
}
if len(t) != 0 {
return 0, fmt.Errorf("leveldb: corrupt log file %q", filename)
}
// TODO: if mem is large enough, write it to a level-0 table and set mem = nil.
batchBuf.Reset()
}
if mem != nil && !mem.Empty() {
meta, err := d.writeLevel0Table(fs, mem)
if err != nil {
return 0, err
}
ve.newFiles = append(ve.newFiles, newFileEntry{level: 0, meta: meta})
// Strictly speaking, it's too early to delete meta.fileNum from d.pendingOutputs,
// but we are replaying the log file, which happens before Open returns, so there
// is no possibility of deleteObsoleteFiles being called concurrently here.
delete(d.pendingOutputs, meta.fileNum)
}
return maxSeqNum, nil
}
