Golang Engine.Clear方法代碼示例

// InternalTruncateLog discards a prefix of the raft log.
func (r *Range) InternalTruncateLog(batch engine.Engine, ms *engine.MVCCStats, args *proto.InternalTruncateLogRequest, reply *proto.InternalTruncateLogResponse) {
	// args.Index is the first index to keep.
	term, err := r.Term(args.Index - 1)
	if err != nil {
		reply.SetGoError(err)
		return
	}
	start := keys.RaftLogKey(r.Desc().RaftID, 0)
	end := keys.RaftLogKey(r.Desc().RaftID, args.Index)
	err = batch.Iterate(engine.MVCCEncodeKey(start), engine.MVCCEncodeKey(end),
		func(kv proto.RawKeyValue) (bool, error) {
			err := batch.Clear(kv.Key)
			return false, err
		})
	if err != nil {
		reply.SetGoError(err)
		return
	}
	ts := proto.RaftTruncatedState{
		Index: args.Index - 1,
		Term:  term,
	}
	err = engine.MVCCPutProto(batch, ms, keys.RaftTruncatedStateKey(r.Desc().RaftID),
		proto.ZeroTimestamp, nil, &ts)
	reply.SetGoError(err)
}

// applySnapshot updates the replica based on the given snapshot.
// Returns the new last index.
func (r *Replica) applySnapshot(batch engine.Engine, snap raftpb.Snapshot) (uint64, error) {
	snapData := roachpb.RaftSnapshotData{}
	err := proto.Unmarshal(snap.Data, &snapData)
	if err != nil {
		return 0, err
	}

	rangeID := r.RangeID

	// First, save the HardState. The HardState must not be changed
	// because it may record a previous vote cast by this node. This is
	// usually unnecessary because a snapshot is nearly always
	// accompanied by a new HardState which incorporates both our former
	// state and new information from the leader, but in the event that
	// the HardState has not changed, we want to use our own previous
	// HardState and not one that was transmitted via the snapshot.
	hardStateKey := keys.RaftHardStateKey(rangeID)
	hardState, _, err := engine.MVCCGet(batch, hardStateKey, roachpb.ZeroTimestamp, true /* consistent */, nil)
	if err != nil {
		return 0, err
	}

	// Extract the updated range descriptor.
	desc := snapData.RangeDescriptor

	// Delete everything in the range and recreate it from the snapshot.
	// We need to delete any old Raft log entries here because any log entries
	// that predate the snapshot will be orphaned and never truncated or GC'd.
	iter := newReplicaDataIterator(&desc, batch, false /* !replicatedOnly */)
	defer iter.Close()
	for ; iter.Valid(); iter.Next() {
		if err := batch.Clear(iter.Key()); err != nil {
			return 0, err
		}
	}

	// Determine the unreplicated key prefix so we can drop any
	// unreplicated keys from the snapshot.
	unreplicatedPrefix := keys.MakeRangeIDUnreplicatedPrefix(desc.RangeID)

	// Write the snapshot into the range.
	for _, kv := range snapData.KV {
		if bytes.HasPrefix(kv.Key, unreplicatedPrefix) {
			continue
		}
		mvccKey := engine.MVCCKey{
			Key:       kv.Key,
			Timestamp: kv.Timestamp,
		}
		if err := batch.Put(mvccKey, kv.Value); err != nil {
			return 0, err
		}
	}

	// Write the snapshot's Raft log into the range.
	if _, err := r.append(batch, 0, snapData.LogEntries); err != nil {
		return 0, err
	}

	// Restore the saved HardState.
	if hardState == nil {
		err := engine.MVCCDelete(batch, nil, hardStateKey, roachpb.ZeroTimestamp, nil)
		if err != nil {
			return 0, err
		}
	} else {
		err := engine.MVCCPut(batch, nil, hardStateKey, roachpb.ZeroTimestamp, *hardState, nil)
		if err != nil {
			return 0, err
		}
	}

	// Read the leader lease.
	lease, err := loadLeaderLease(batch, desc.RangeID)
	if err != nil {
		return 0, err
	}

	// Load updated range stats. The local newStats variable will be assigned
	// to r.stats after the batch commits.
	newStats, err := newRangeStats(desc.RangeID, batch)
	if err != nil {
		return 0, err
	}

	// The next line sets the persisted last index to the last applied index.
	// This is not a correctness issue, but means that we may have just
	// transferred some entries we're about to re-request from the leader and
	// overwrite.
	// However, raft.MultiNode currently expects this behaviour, and the
	// performance implications are not likely to be drastic. If our feelings
	// about this ever change, we can add a LastIndex field to
	// raftpb.SnapshotMetadata.
	if err := setLastIndex(batch, rangeID, snap.Metadata.Index); err != nil {
		return 0, err
	}

	batch.Defer(func() {
//.........這裏部分代碼省略.........