func loadRangeDescriptor(
	db engine.Engine, rangeID roachpb.RangeID,
) (roachpb.RangeDescriptor, error) {
	var desc roachpb.RangeDescriptor
	handleKV := func(kv engine.MVCCKeyValue) (bool, error) {
		if kv.Key.Timestamp == hlc.ZeroTimestamp {
			// We only want values, not MVCCMetadata.
			return false, nil
		}
		if err := checkRangeDescriptorKey(kv.Key); err != nil {
			// Range descriptor keys are interleaved with others, so if it
			// doesn't parse as a range descriptor just skip it.
			return false, nil
		}
		if err := getProtoValue(kv.Value, &desc); err != nil {
			return false, err
		}
		return desc.RangeID == rangeID, nil
	}

	// Range descriptors are stored by key, so we have to scan over the
	// range-local data to find the one for this RangeID.
	start := engine.MakeMVCCMetadataKey(keys.LocalRangePrefix)
	end := engine.MakeMVCCMetadataKey(keys.LocalRangeMax)

	if err := db.Iterate(start, end, handleKV); err != nil {
		return roachpb.RangeDescriptor{}, err
	}
	if desc.RangeID == rangeID {
		return desc, nil
	}
	return roachpb.RangeDescriptor{}, fmt.Errorf("range descriptor %d not found", rangeID)
}

// ClearData removes all persisted items stored in the cache.
func (sc *AbortCache) ClearData(e engine.Engine) error {
	b := e.NewBatch()
	defer b.Close()
	_, err := engine.ClearRange(b, engine.MakeMVCCMetadataKey(sc.min()), engine.MakeMVCCMetadataKey(sc.max()))
	if err != nil {
		return err
	}
	return b.Commit()
}

// ClearData removes all persisted items stored in the cache.
func (sc *AbortCache) ClearData(e engine.Engine) error {
	iter := e.NewIterator(false)
	defer iter.Close()
	b := e.NewWriteOnlyBatch()
	defer b.Close()
	err := b.ClearRange(iter, engine.MakeMVCCMetadataKey(sc.min()),
		engine.MakeMVCCMetadataKey(sc.max()))
	if err != nil {
		return err
	}
	return b.Commit()
}

func verifyCleanup(key roachpb.Key, coord *TxnCoordSender, eng engine.Engine, t *testing.T) {
	util.SucceedsSoon(t, func() error {
		coord.Lock()
		l := len(coord.txns)
		coord.Unlock()
		if l != 0 {
			return fmt.Errorf("expected empty transactions map; got %d", l)
		}
		meta := &enginepb.MVCCMetadata{}
		ok, _, _, err := eng.GetProto(engine.MakeMVCCMetadataKey(key), meta)
		if err != nil {
			return fmt.Errorf("error getting MVCC metadata: %s", err)
		}
		if ok && meta.Txn != nil {
			return fmt.Errorf("found unexpected write intent: %s", meta)
		}
		return nil
	})
}