Golang Call.Seek方法代码示例

// Begin will set up the mapper to run the map function for a given aggregate call starting at the passed in time
func (l *LocalMapper) Begin(c *influxql.Call, startingTime int64) error {
	// set up the buffers. These ensure that we return data in time order
	mapFunc, err := influxql.InitializeMapFunc(c)
	if err != nil {
		return err
	}
	l.mapFunc = mapFunc
	l.keyBuffer = make([]int64, len(l.cursors))
	l.valueBuffer = make([][]byte, len(l.cursors))
	l.tmin = startingTime

	// determine if this is a raw data query with a single field, multiple fields, or an aggregate
	var fieldName string
	if c == nil { // its a raw data query
		l.isRaw = true
		if len(l.selectFields) == 1 {
			fieldName = l.selectFields[0].Name
		}
	} else {
		lit, ok := c.Args[0].(*influxql.VarRef)
		if !ok {
			return fmt.Errorf("aggregate call didn't contain a field %s", c.String())
		}
		fieldName = lit.Val
	}

	// set up the field info if a specific field was set for this mapper
	if fieldName != "" {
		f := l.decoder.FieldByName(fieldName)
		if f == nil {
			return fmt.Errorf("%s isn't a field on measurement %s", fieldName, l.job.MeasurementName)
		}
		l.fieldID = f.ID
		l.fieldName = f.Name
	}

	// seek the bolt cursors and fill the buffers
	for i, c := range l.cursors {
		// this series may have never been written in this shard group (time range) so the cursor would be nil
		if c == nil {
			l.keyBuffer[i] = 0
			l.valueBuffer[i] = nil
			continue
		}
		k, v := c.Seek(u64tob(uint64(l.job.TMin)))
		if k == nil {
			l.keyBuffer[i] = 0
			l.valueBuffer[i] = nil
			continue
		}
		l.cursorsEmpty = false
		t := int64(btou64(k))
		l.keyBuffer[i] = t
		l.valueBuffer[i] = v
	}
	return nil
}

// Begin will set up the mapper to run the map function for a given aggregate call starting at the passed in time
func (l *LocalMapper) Begin(c *influxql.Call, startingTime int64, chunkSize int) error {
	// set up the buffers. These ensure that we return data in time order
	mapFunc, err := influxql.InitializeMapFunc(c)
	if err != nil {
		return err
	}
	l.mapFunc = mapFunc
	l.keyBuffer = make([]int64, len(l.cursors))
	l.valueBuffer = make([][]byte, len(l.cursors))
	l.chunkSize = chunkSize
	l.tmin = startingTime

	var isCountDistinct bool

	// determine if this is a raw data query with a single field, multiple fields, or an aggregate
	var fieldName string
	if c == nil { // its a raw data query
		l.isRaw = true
		if len(l.selectFields) == 1 {
			fieldName = l.selectFields[0]
		}

		// if they haven't set a limit, just set it to the max int size
		if l.limit == 0 {
			l.limit = math.MaxUint64
		}
	} else {
		// Check for calls like `derivative(mean(value), 1d)`
		var nested *influxql.Call = c
		if fn, ok := c.Args[0].(*influxql.Call); ok {
			nested = fn
		}

		switch lit := nested.Args[0].(type) {
		case *influxql.VarRef:
			fieldName = lit.Val
		case *influxql.Distinct:
			if c.Name != "count" {
				return fmt.Errorf("aggregate call didn't contain a field %s", c.String())
			}
			isCountDistinct = true
			fieldName = lit.Val
		default:
			return fmt.Errorf("aggregate call didn't contain a field %s", c.String())
		}

		isCountDistinct = isCountDistinct || (c.Name == "count" && nested.Name == "distinct")
	}

	// set up the field info if a specific field was set for this mapper
	if fieldName != "" {
		fid, err := l.decoder.FieldIDByName(fieldName)
		if err != nil {
			switch {
			case c != nil && c.Name == "distinct":
				return fmt.Errorf(`%s isn't a field on measurement %s; to query the unique values for a tag use SHOW TAG VALUES FROM %[2]s WITH KEY = "%[1]s`, fieldName, l.job.MeasurementName)
			case isCountDistinct:
				return fmt.Errorf("%s isn't a field on measurement %s; count(distinct) on tags isn't yet supported", fieldName, l.job.MeasurementName)
			}
		}
		l.fieldID = fid
		l.fieldName = fieldName
	}

	// seek the bolt cursors and fill the buffers
	for i, c := range l.cursors {
		// this series may have never been written in this shard group (time range) so the cursor would be nil
		if c == nil {
			l.keyBuffer[i] = 0
			l.valueBuffer[i] = nil
			continue
		}
		k, v := c.Seek(u64tob(uint64(l.job.TMin)))
		if k == nil {
			l.keyBuffer[i] = 0
			l.valueBuffer[i] = nil
			continue
		}
		l.cursorsEmpty = false
		t := int64(btou64(k))
		l.keyBuffer[i] = t
		l.valueBuffer[i] = v
	}
	return nil
}