Golang SelectQuery.IsSinglePointQuery方法代码示例

func (self *LevelDbDatastore) executeQueryForSeries(database, series string, columns []string,
	query *parser.SelectQuery, yield func(*protocol.Series) error,
	ringFilter func(database, series *string, time *int64) bool) error {

	startTimeBytes, endTimeBytes := self.byteArraysForStartAndEndTimes(common.TimeToMicroseconds(query.GetStartTime()), common.TimeToMicroseconds(query.GetEndTime()))
	emptyResult := &protocol.Series{Name: &series, Points: nil}

	fields, err := self.getFieldsForSeries(database, series, columns)
	if err != nil {
		// because a db is distributed across the cluster, it's possible we don't have the series indexed here. ignore
		switch err := err.(type) {
		case FieldLookupError:
			return yield(emptyResult)
		default:
			return err
		}
	}

	fieldCount := len(fields)
	rawColumnValues := make([]*rawColumnValue, fieldCount, fieldCount)

	if query.IsSinglePointQuery() {
		result, err := self.fetchSinglePoint(database, series, fields, query)
		if err != nil {
			return err
		}

		if err := yield(result); err != nil {
			return err
		}
		return nil
	}

	fieldNames, iterators := self.getIterators(fields, startTimeBytes, endTimeBytes, query.Ascending)
	result := &protocol.Series{Name: &series, Fields: fieldNames, Points: make([]*protocol.Point, 0)}

	limit := query.Limit
	shouldLimit := true
	if limit == 0 {
		limit = -1
		shouldLimit = false
	}
	resultByteCount := 0

	// TODO: clean up, this is super gnarly
	// optimize for the case where we're pulling back only a single column or aggregate
	for {
		isValid := false
		point := &protocol.Point{Values: make([]*protocol.FieldValue, fieldCount, fieldCount)}

		for i, it := range iterators {
			if rawColumnValues[i] != nil || !it.Valid() {
				continue
			}

			key := it.Key()
			if len(key) < 16 {
				continue
			}

			if !isPointInRange(fields[i].Id, startTimeBytes, endTimeBytes, key) {
				continue
			}

			value := it.Value()
			sequenceNumber := key[16:]

			rawTime := key[8:16]
			rawValue := &rawColumnValue{time: rawTime, sequence: sequenceNumber, value: value}
			rawColumnValues[i] = rawValue
		}

		var pointTimeRaw []byte
		var pointSequenceRaw []byte
		// choose the highest (or lowest in case of ascending queries) timestamp
		// and sequence number. that will become the timestamp and sequence of
		// the next point.
		for _, value := range rawColumnValues {
			if value == nil {
				continue
			}

			pointTimeRaw, pointSequenceRaw = value.updatePointTimeAndSequence(pointTimeRaw,
				pointSequenceRaw, query.Ascending)
		}

		for i, iterator := range iterators {
			// if the value is nil or doesn't match the point's timestamp and sequence number
			// then skip it
			if rawColumnValues[i] == nil ||
				!bytes.Equal(rawColumnValues[i].time, pointTimeRaw) ||
				!bytes.Equal(rawColumnValues[i].sequence, pointSequenceRaw) {

				point.Values[i] = &protocol.FieldValue{IsNull: &TRUE}
				continue
			}

			// if we emitted at lease one column, then we should keep
			// trying to get more points
			isValid = true
//.........这里部分代码省略.........