// append the given entries to the raft log. Takes the previous values of
// r.mu.lastIndex and r.mu.raftLogSize, and returns new values. We do this
// rather than modifying them directly because these modifications need to be
// atomic with the commit of the batch.
func (r *Replica) append(
	ctx context.Context,
	batch engine.ReadWriter,
	prevLastIndex uint64,
	prevRaftLogSize int64,
	entries []raftpb.Entry,
) (uint64, int64, error) {
	if len(entries) == 0 {
		return prevLastIndex, prevRaftLogSize, nil
	}
	var diff enginepb.MVCCStats
	var value roachpb.Value
	for i := range entries {
		ent := &entries[i]
		key := keys.RaftLogKey(r.RangeID, ent.Index)
		if err := value.SetProto(ent); err != nil {
			return 0, 0, err
		}
		value.InitChecksum(key)
		var err error
		if ent.Index > prevLastIndex {
			err = engine.MVCCBlindPut(ctx, batch, &diff, key, hlc.ZeroTimestamp, value, nil /* txn */)
		} else {
			err = engine.MVCCPut(ctx, batch, &diff, key, hlc.ZeroTimestamp, value, nil /* txn */)
		}
		if err != nil {
			return 0, 0, err
		}
	}

	// Delete any previously appended log entries which never committed.
	lastIndex := entries[len(entries)-1].Index
	for i := lastIndex + 1; i <= prevLastIndex; i++ {
		err := engine.MVCCDelete(ctx, batch, &diff, keys.RaftLogKey(r.RangeID, i),
			hlc.ZeroTimestamp, nil /* txn */)
		if err != nil {
			return 0, 0, err
		}
	}

	if err := setLastIndex(ctx, batch, r.RangeID, lastIndex); err != nil {
		return 0, 0, err
	}

	raftLogSize := prevRaftLogSize + diff.SysBytes

	return lastIndex, raftLogSize, nil
}
// createRangeData creates sample range data in all possible areas of
// the key space. Returns a slice of the encoded keys of all created
// data.
func createRangeData(t *testing.T, r *Replica) []engine.MVCCKey {
	ts0 := hlc.ZeroTimestamp
	ts := hlc.Timestamp{WallTime: 1}
	desc := r.Desc()
	keyTSs := []struct {
		key roachpb.Key
		ts  hlc.Timestamp
	}{
		{keys.AbortCacheKey(r.RangeID, testTxnID), ts0},
		{keys.AbortCacheKey(r.RangeID, testTxnID2), ts0},
		{keys.RangeFrozenStatusKey(r.RangeID), ts0},
		{keys.RangeLastGCKey(r.RangeID), ts0},
		{keys.RaftAppliedIndexKey(r.RangeID), ts0},
		{keys.RaftTruncatedStateKey(r.RangeID), ts0},
		{keys.RangeLeaseKey(r.RangeID), ts0},
		{keys.LeaseAppliedIndexKey(r.RangeID), ts0},
		{keys.RangeStatsKey(r.RangeID), ts0},
		{keys.RangeTxnSpanGCThresholdKey(r.RangeID), ts0},
		{keys.RaftHardStateKey(r.RangeID), ts0},
		{keys.RaftLastIndexKey(r.RangeID), ts0},
		{keys.RaftLogKey(r.RangeID, 1), ts0},
		{keys.RaftLogKey(r.RangeID, 2), ts0},
		{keys.RangeLastReplicaGCTimestampKey(r.RangeID), ts0},
		{keys.RangeLastVerificationTimestampKeyDeprecated(r.RangeID), ts0},
		{keys.RangeDescriptorKey(desc.StartKey), ts},
		{keys.TransactionKey(roachpb.Key(desc.StartKey), uuid.MakeV4()), ts0},
		{keys.TransactionKey(roachpb.Key(desc.StartKey.Next()), uuid.MakeV4()), ts0},
		{keys.TransactionKey(fakePrevKey(desc.EndKey), uuid.MakeV4()), ts0},
		// TODO(bdarnell): KeyMin.Next() results in a key in the reserved system-local space.
		// Once we have resolved https://github.com/cockroachdb/cockroach/issues/437,
		// replace this with something that reliably generates the first valid key in the range.
		//{r.Desc().StartKey.Next(), ts},
		// The following line is similar to StartKey.Next() but adds more to the key to
		// avoid falling into the system-local space.
		{append(append([]byte{}, desc.StartKey...), '\x02'), ts},
		{fakePrevKey(r.Desc().EndKey), ts},
	}

	keys := []engine.MVCCKey{}
	for _, keyTS := range keyTSs {
		if err := engine.MVCCPut(context.Background(), r.store.Engine(), nil, keyTS.key, keyTS.ts, roachpb.MakeValueFromString("value"), nil); err != nil {
			t.Fatal(err)
		}
		keys = append(keys, engine.MVCCKey{Key: keyTS.key, Timestamp: keyTS.ts})
	}
	return keys
}
func iterateEntries(
	ctx context.Context,
	e engine.Reader,
	rangeID roachpb.RangeID,
	lo,
	hi uint64,
	scanFunc func(roachpb.KeyValue) (bool, error),
) error {
	_, err := engine.MVCCIterate(
		ctx, e,
		keys.RaftLogKey(rangeID, lo),
		keys.RaftLogKey(rangeID, hi),
		hlc.ZeroTimestamp,
		true,  /* consistent */
		nil,   /* txn */
		false, /* !reverse */
		scanFunc,
	)
	return err
}