influxdb/tsdb/meta.go

package tsdb

import (
	"fmt"
	"regexp"
	"sort"
	"sync"
	"unsafe"

	"github.com/influxdata/influxdb/influxql"
	"github.com/influxdata/influxdb/models"
	"github.com/influxdata/influxdb/pkg/escape"
	internal "github.com/influxdata/influxdb/tsdb/internal"

	"github.com/gogo/protobuf/proto"
)

//go:generate protoc --gogo_out=. internal/meta.proto

/*
// DatabaseIndex is the in memory index of a collection of measurements, time series, and their tags.
// Exported functions are goroutine safe while un-exported functions assume the caller will use the appropriate locks.
type DatabaseIndex struct {
	// in memory metadata index, built on load and updated when new series come in
	mu           sync.RWMutex
	measurements map[string]*Measurement // measurement name to object and index
	series       map[string]*Series      // map series key to the Series object
	lastID       uint64                  // last used series ID. They're in memory only for this shard

	seriesSketch, seriesTSSketch             *hll.Plus
	measurementsSketch, measurementsTSSketch *hll.Plus

	name string // name of the database represented by this index
}

// NewDatabaseIndex returns a new initialized DatabaseIndex.
func NewDatabaseIndex(name string) (index *DatabaseIndex, err error) {
	index = &DatabaseIndex{
		measurements: make(map[string]*Measurement),
		series:       make(map[string]*Series),
		name:         name,
	}

	if index.seriesSketch, err = hll.NewPlus(16); err != nil {
		return nil, err
	} else if index.seriesTSSketch, err = hll.NewPlus(16); err != nil {
		return nil, err
	} else if index.measurementsSketch, err = hll.NewPlus(16); err != nil {
		return nil, err
	} else if index.measurementsTSSketch, err = hll.NewPlus(16); err != nil {
		return nil, err
	}

	return index, nil
}

func (d *DatabaseIndex) Open() (err error) { return nil }
func (d *DatabaseIndex) Close() error      { return nil }

// Series returns a series by key.
func (d *DatabaseIndex) Series(key []byte) (*Series, error) {
	d.mu.RLock()
	s := d.series[string(key)]
	d.mu.RUnlock()
	return s, nil
}

// SeriesN returns the exact number of series in the index.
func (d *DatabaseIndex) SeriesN() (uint64, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return uint64(len(d.series)), nil
}

// SeriesSketch returns the sketch for the series.
func (d *DatabaseIndex) SeriesSketches() (estimator.Sketch, estimator.Sketch, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.seriesSketch, d.seriesTSSketch, nil
}

// Measurement returns the measurement object from the index by the name
func (d *DatabaseIndex) Measurement(name []byte) (*Measurement, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.measurements[string(name)], nil
}

// MeasurementsSketch returns the sketch for the series.
func (d *DatabaseIndex) MeasurementsSketches() (estimator.Sketch, estimator.Sketch, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.measurementsSketch, d.measurementsTSSketch, nil
}

// MeasurementsByName returns a list of measurements.
func (d *DatabaseIndex) MeasurementsByName(names []string) ([]*Measurement, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()

	a := make([]*Measurement, 0, len(names))
	for _, name := range names {
		if m := d.measurements[name]; m != nil {
			a = append(a, m)
		}
	}
	return a, nil
}

// MeasurementSeriesCounts returns the number of measurements and series currently indexed by the database.
// Useful for reporting and monitoring.
func (d *DatabaseIndex) MeasurementSeriesCounts() (nMeasurements int, nSeries int) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	nMeasurements, nSeries = len(d.measurements), len(d.series)
	return
}

// SeriesShardN returns the series count for a shard.
func (d *DatabaseIndex) SeriesShardN(shardID uint64) int {
	var n int
	d.mu.RLock()
	for _, s := range d.series {
		if s.Assigned(shardID) {
			n++
		}
	}
	d.mu.RUnlock()
	return n
}

// CreateSeriesIndexIfNotExists adds the series for the given measurement to the
// index and sets its ID or returns the existing series object
func (d *DatabaseIndex) CreateSeriesIndexIfNotExists(measurementName string, series *Series) (*Series, error) {
	d.mu.RLock()
	// if there is a measurement for this id, it's already been added
	ss := d.series[series.Key]
	if ss != nil {
		d.mu.RUnlock()
		return ss, nil
	}
	d.mu.RUnlock()

	// get or create the measurement index
	m, err := d.CreateMeasurementIndexIfNotExists(measurementName)
	if err != nil {
		return nil, err
	}

	d.mu.Lock()
	// Check for the series again under a write lock
	ss = d.series[series.Key]
	if ss != nil {
		d.mu.Unlock()
		return ss, nil
	}

	// set the in memory ID for query processing on this shard
	series.ID = d.lastID + 1
	d.lastID++

	series.measurement = m
	d.series[series.Key] = series

	m.AddSeries(series)

	// Add the series to the series sketch.
	d.seriesSketch.Add([]byte(series.Key))
	d.mu.Unlock()

	return series, nil
}

// CreateMeasurementIndexIfNotExists creates or retrieves an in memory index
// object for the measurement
func (d *DatabaseIndex) CreateMeasurementIndexIfNotExists(name string) (*Measurement, error) {
	name = escape.UnescapeString(name)

	// See if the measurement exists using a read-lock
	d.mu.RLock()
	m := d.measurements[name]
	if m != nil {
		d.mu.RUnlock()
		return m, nil
	}
	d.mu.RUnlock()

	// Doesn't exist, so lock the index to create it
	d.mu.Lock()
	defer d.mu.Unlock()

	// Make sure it was created in between the time we released our read-lock
	// and acquire the write lock
	m = d.measurements[name]
	if m == nil {
		m = NewMeasurement(name)
		d.measurements[name] = m

		// Add the measurement to the measurements sketch.
		d.measurementsSketch.Add([]byte(name))
	}
	return m, nil
}

// TagsForSeries returns the tag map for the passed in series
func (d *DatabaseIndex) TagsForSeries(key string) (models.Tags, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()

	ss := d.series[key]
	if ss == nil {
		return nil, nil
	}
	return ss.Tags, nil
}

// MeasurementsByExpr takes an expression containing only tags and returns a
// list of matching *Measurement. The bool return argument returns if the
// expression was a measurement expression. It is used to differentiate a list
// of no measurements because all measurements were filtered out (when the bool
// is true) against when there are no measurements because the expression
// wasn't evaluated (when the bool is false).
func (d *DatabaseIndex) MeasurementsByExpr(expr influxql.Expr) (Measurements, bool, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	return d.measurementsByExpr(expr)
}

func (d *DatabaseIndex) measurementsByExpr(expr influxql.Expr) (Measurements, bool, error) {
	if expr == nil {
		return nil, false, nil
	}

	switch e := expr.(type) {
	case *influxql.BinaryExpr:
		switch e.Op {
		case influxql.EQ, influxql.NEQ, influxql.EQREGEX, influxql.NEQREGEX:
			tag, ok := e.LHS.(*influxql.VarRef)
			if !ok {
				return nil, false, fmt.Errorf("left side of '%s' must be a tag key", e.Op.String())
			}

			tf := &TagFilter{
				Op:  e.Op,
				Key: tag.Val,
			}

			if influxql.IsRegexOp(e.Op) {
				re, ok := e.RHS.(*influxql.RegexLiteral)
				if !ok {
					return nil, false, fmt.Errorf("right side of '%s' must be a regular expression", e.Op.String())
				}
				tf.Regex = re.Val
			} else {
				s, ok := e.RHS.(*influxql.StringLiteral)
				if !ok {
					return nil, false, fmt.Errorf("right side of '%s' must be a tag value string", e.Op.String())
				}
				tf.Value = s.Val
			}

			// Match on name, if specified.
			if tag.Val == "_name" {
				return d.measurementsByNameFilter(tf.Op, tf.Value, tf.Regex), true, nil
			} else if influxql.IsSystemName(tag.Val) {
				return nil, false, nil
			}

			return d.measurementsByTagFilters([]*TagFilter{tf}), true, nil
		case influxql.OR, influxql.AND:
			lhsIDs, lhsOk, err := d.measurementsByExpr(e.LHS)
			if err != nil {
				return nil, false, err
			}

			rhsIDs, rhsOk, err := d.measurementsByExpr(e.RHS)
			if err != nil {
				return nil, false, err
			}

			if lhsOk && rhsOk {
				if e.Op == influxql.OR {
					return lhsIDs.union(rhsIDs), true, nil
				}

				return lhsIDs.intersect(rhsIDs), true, nil
			} else if lhsOk {
				return lhsIDs, true, nil
			} else if rhsOk {
				return rhsIDs, true, nil
			}
			return nil, false, nil
		default:
			return nil, false, fmt.Errorf("invalid tag comparison operator")
		}
	case *influxql.ParenExpr:
		return d.measurementsByExpr(e.Expr)
	}
	return nil, false, fmt.Errorf("%#v", expr)
}

// measurementsByNameFilter returns the sorted measurements matching a name.
func (d *DatabaseIndex) measurementsByNameFilter(op influxql.Token, val string, regex *regexp.Regexp) Measurements {
	var measurements Measurements
	for _, m := range d.measurements {
		var matched bool
		switch op {
		case influxql.EQ:
			matched = m.Name == val
		case influxql.NEQ:
			matched = m.Name != val
		case influxql.EQREGEX:
			matched = regex.MatchString(m.Name)
		case influxql.NEQREGEX:
			matched = !regex.MatchString(m.Name)
		}

		if !matched {
			continue
		}
		measurements = append(measurements, m)
	}
	sort.Sort(measurements)
	return measurements
}

// measurementsByTagFilters returns the sorted measurements matching the filters on tag values.
func (d *DatabaseIndex) measurementsByTagFilters(filters []*TagFilter) Measurements {
	// If no filters, then return all measurements.
	if len(filters) == 0 {
		measurements := make(Measurements, 0, len(d.measurements))
		for _, m := range d.measurements {
			measurements = append(measurements, m)
		}
		return measurements
	}

	// Build a list of measurements matching the filters.
	var measurements Measurements
	var tagMatch bool

	// Iterate through all measurements in the database.
	for _, m := range d.measurements {
		// Iterate filters seeing if the measurement has a matching tag.
		for _, f := range filters {
			m.mu.RLock()
			tagVals, ok := m.seriesByTagKeyValue[f.Key]
			m.mu.RUnlock()
			if !ok {
				continue
			}

			tagMatch = false

			// If the operator is non-regex, only check the specified value.
			if f.Op == influxql.EQ || f.Op == influxql.NEQ {
				if _, ok := tagVals[f.Value]; ok {
					tagMatch = true
				}
			} else {
				// Else, the operator is a regex and we have to check all tag
				// values against the regular expression.
				for tagVal := range tagVals {
					if f.Regex.MatchString(tagVal) {
						tagMatch = true
						break
					}
				}
			}

			isEQ := (f.Op == influxql.EQ || f.Op == influxql.EQREGEX)

			//
			// XNOR gate
			//
			// tags match | operation is EQ | measurement matches
			// --------------------------------------------------
			//     True   |       True      |      True
			//     True   |       False     |      False
			//     False  |       True      |      False
			//     False  |       False     |      True

			if tagMatch == isEQ {
				measurements = append(measurements, m)
				break
			}
		}
	}

	sort.Sort(measurements)
	return measurements
}

// MeasurementNamesByRegex returns the measurements that match the regex.
func (d *DatabaseIndex) MeasurementNamesByRegex(re *regexp.Regexp) ([][]byte, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()

	var matches [][]byte
	for _, m := range d.measurements {
		if re.MatchString(m.Name) {
			matches = append(matches,[]byte(m.Name))
		}
	}
	return matches, nil
}

// Measurements returns a list of all measurements.
func (d *DatabaseIndex) Measurements() (Measurements, error) {
	d.mu.RLock()
	measurements := make(Measurements, 0, len(d.measurements))
	for _, m := range d.measurements {
		measurements = append(measurements, m)
	}
	d.mu.RUnlock()

	return measurements, nil
}

// DropMeasurement removes the measurement and all of its underlying
// series from the database index
func (d *DatabaseIndex) DropMeasurement(name []byte) error {
	d.mu.Lock()
	defer d.mu.Unlock()
	return d.dropMeasurement(string(name))
}

func (d *DatabaseIndex) dropMeasurement(name string) error {
	// Update the tombstone sketch.
	d.measurementsTSSketch.Add([]byte(name))

	m := d.measurements[name]
	if m == nil {
		return nil
	}

	delete(d.measurements, name)
	for _, s := range m.seriesByID {
		delete(d.series, s.Key)
	}
	return nil
}

// DropSeries removes the series keys and their tags from the index
func (d *DatabaseIndex) DropSeries(keys []string) error {
	if len(keys) == 0 {
		return nil
	}

	d.mu.Lock()
	defer d.mu.Unlock()

	var (
		mToDelete = map[string]struct{}{}
		nDeleted  int64
	)

	for _, k := range keys {
		// Update the tombstone sketch.
		d.seriesTSSketch.Add([]byte(k))

		series := d.series[k]
		if series == nil {
			continue
		}
		series.measurement.DropSeries(series)
		delete(d.series, k)
		nDeleted++

		// If there are no more series in the measurement then we'll
		// remove it.
		if len(series.measurement.seriesByID) == 0 {
			mToDelete[series.measurement.Name] = struct{}{}
		}
	}

	for mname := range mToDelete {
		d.dropMeasurement(mname)
	}
	return nil
}

// Dereference removes all references to data within b and moves them to the heap.
func (d *DatabaseIndex) Dereference(b []byte) {
	d.mu.RLock()
	defer d.mu.RUnlock()

	for _, s := range d.series {
		s.Dereference(b)
	}
}
*/

// Measurement represents a collection of time series in a database. It also
// contains in memory structures for indexing tags. Exported functions are
// goroutine safe while un-exported functions assume the caller will use the
// appropriate locks.
type Measurement struct {
	mu         sync.RWMutex
	Name       string `json:"name,omitempty"`
	fieldNames map[string]struct{}

	// in-memory index fields
	seriesByID          map[uint64]*Series              // lookup table for series by their id
	seriesByTagKeyValue map[string]map[string]SeriesIDs // map from tag key to value to sorted set of series ids
	seriesIDs           SeriesIDs                       // sorted list of series IDs in this measurement
}

// NewMeasurement allocates and initializes a new Measurement.
func NewMeasurement(name string) *Measurement {
	return &Measurement{
		Name:       name,
		fieldNames: make(map[string]struct{}),

		seriesByID:          make(map[uint64]*Series),
		seriesByTagKeyValue: make(map[string]map[string]SeriesIDs),
		seriesIDs:           make(SeriesIDs, 0, 1),
	}
}

func (m *Measurement) hasField(name string) bool {
	_, hasField := m.fieldNames[name]
	return hasField
}

// SeriesByID returns a series by identifier.
func (m *Measurement) SeriesByID(id uint64) *Series {
	m.mu.RLock()
	defer m.mu.RUnlock()
	return m.seriesByID[id]
}

// SeriesByIDSlice returns a list of series by identifiers.
func (m *Measurement) SeriesByIDSlice(ids []uint64) []*Series {
	m.mu.RLock()
	defer m.mu.RUnlock()
	a := make([]*Series, len(ids))
	for i, id := range ids {
		a[i] = m.seriesByID[id]
	}
	return a
}

// AppendSeriesKeysByID appends keys for a list of series ids to a buffer.
func (m *Measurement) AppendSeriesKeysByID(dst []string, ids []uint64) []string {
	m.mu.RLock()
	defer m.mu.RUnlock()
	for _, id := range ids {
		if s := m.seriesByID[id]; s != nil {
			dst = append(dst, s.Key)
		}
	}
	return dst
}

// SeriesKeys returns the keys of every series in this measurement
func (m *Measurement) SeriesKeys() [][]byte {
	m.mu.RLock()
	defer m.mu.RUnlock()
	keys := make([][]byte, 0, len(m.seriesByID))
	for _, s := range m.seriesByID {
		keys = append(keys, []byte(s.Key))
	}
	return keys
}

// HasTagKey returns true if at least one series in this measurement has written a value for the passed in tag key
func (m *Measurement) HasTagKey(k string) bool {
	m.mu.RLock()
	defer m.mu.RUnlock()
	_, hasTag := m.seriesByTagKeyValue[k]
	return hasTag
}

// HasTagKeyValue returns true if at least one series in this measurement has written a value the given tag key and tag value.
func (m *Measurement) HasTagKeyValue(k, v []byte) bool {
	m.mu.RLock()
	if vals, ok := m.seriesByTagKeyValue[string(k)]; ok {
		_, ok := vals[string(v)]
		m.mu.RUnlock()
		return ok
	}
	m.mu.RUnlock()
	return false
}

// HasSeries returns true if there is at least 1 series under this measurement.
func (m *Measurement) HasSeries() bool {
	m.mu.RLock()
	defer m.mu.RUnlock()
	return len(m.seriesByID) > 0
}

// Cardinality returns the number of values associated with the given tag key.
func (m *Measurement) Cardinality(key string) int {
	var n int
	m.mu.RLock()
	n = len(m.seriesByTagKeyValue[key])
	m.mu.RUnlock()
	return n
}

// CardinalityBytes returns the number of values associated with tag key
func (m *Measurement) CardinalityBytes(key []byte) int {
	var n int
	m.mu.RLock()
	n = len(m.seriesByTagKeyValue[string(key)])
	m.mu.RUnlock()
	return n
}

// AddSeries adds a series to the measurement's index.
// It returns true if the series was added successfully or false if the series was already present.
func (m *Measurement) AddSeries(s *Series) bool {
	m.mu.RLock()
	if _, ok := m.seriesByID[s.ID]; ok {
		m.mu.RUnlock()
		return false
	}
	m.mu.RUnlock()

	m.mu.Lock()
	defer m.mu.Unlock()

	if _, ok := m.seriesByID[s.ID]; ok {
		return false
	}

	m.seriesByID[s.ID] = s
	m.seriesIDs = append(m.seriesIDs, s.ID)

	// the series ID should always be higher than all others because it's a new
	// series. So don't do the sort if we don't have to.
	if len(m.seriesIDs) > 1 && m.seriesIDs[len(m.seriesIDs)-1] < m.seriesIDs[len(m.seriesIDs)-2] {
		sort.Sort(m.seriesIDs)
	}

	// add this series id to the tag index on the measurement
	for _, t := range s.Tags {
		valueMap := m.seriesByTagKeyValue[string(t.Key)]
		if valueMap == nil {
			valueMap = make(map[string]SeriesIDs)
			m.seriesByTagKeyValue[string(t.Key)] = valueMap
		}
		ids := valueMap[string(t.Value)]
		ids = append(ids, s.ID)

		// most of the time the series ID will be higher than all others because it's a new
		// series. So don't do the sort if we don't have to.
		if len(ids) > 1 && ids[len(ids)-1] < ids[len(ids)-2] {
			sort.Sort(ids)
		}
		valueMap[string(t.Value)] = ids
	}

	return true
}

// DropSeries removes a series from the measurement's index.
func (m *Measurement) DropSeries(series *Series) {
	seriesID := series.ID
	m.mu.Lock()
	defer m.mu.Unlock()

	if _, ok := m.seriesByID[seriesID]; !ok {
		return
	}
	delete(m.seriesByID, seriesID)

	ids := filter(m.seriesIDs, seriesID)
	m.seriesIDs = ids

	// remove this series id from the tag index on the measurement
	// s.seriesByTagKeyValue is defined as map[string]map[string]SeriesIDs
	for _, t := range series.Tags {
		values := m.seriesByTagKeyValue[string(t.Key)][string(t.Value)]
		ids := filter(values, seriesID)
		// Check to see if we have any ids, if not, remove the key
		if len(ids) == 0 {
			delete(m.seriesByTagKeyValue[string(t.Key)], string(t.Value))
		} else {
			m.seriesByTagKeyValue[string(t.Key)][string(t.Value)] = ids
		}

		// If we have no values, then we delete the key
		if len(m.seriesByTagKeyValue[string(t.Key)]) == 0 {
			delete(m.seriesByTagKeyValue, string(t.Key))
		}
	}

	return
}

// TagSets returns the unique tag sets that exist for the given tag keys. This
// is used to determine what composite series will be created by a group by.
//
// i.e. "group by region" should return: {"region":"uswest"},
// {"region":"useast"} or region, service returns {"region": "uswest",
// "service": "redis"}, {"region": "uswest", "service": "mysql"}, etc...
//
// This will also populate the TagSet objects with the series IDs that match
// each tagset and any influx filter expression that goes with the series TODO:
// this shouldn't be exported. However, until tx.go and the engine get
// refactored into tsdb, we need it.
func (m *Measurement) TagSets(dimensions []string, condition influxql.Expr) ([]*influxql.TagSet, error) {
	panic("MOVED")
}

// IDsForExpr returns the series IDs that are candidates to match the given expression.
func (m *Measurement) IDsForExpr(n *influxql.BinaryExpr) SeriesIDs {
	ids, _, _ := m.idsForExpr(n)
	return ids
}

// idsForExpr returns a collection of series ids and a filter expression that should
// be used to filter points from those series.
func (m *Measurement) idsForExpr(n *influxql.BinaryExpr) (SeriesIDs, influxql.Expr, error) {
	// If this binary expression has another binary expression, then this
	// is some expression math and we should just pass it to the underlying query.
	if _, ok := n.LHS.(*influxql.BinaryExpr); ok {
		return m.seriesIDs, n, nil
	} else if _, ok := n.RHS.(*influxql.BinaryExpr); ok {
		return m.seriesIDs, n, nil
	}

	// Retrieve the variable reference from the correct side of the expression.
	name, ok := n.LHS.(*influxql.VarRef)
	value := n.RHS
	if !ok {
		name, ok = n.RHS.(*influxql.VarRef)
		if !ok {
			return nil, nil, fmt.Errorf("invalid expression: %s", n.String())
		}
		value = n.LHS
	}

	// For time literals, return all series IDs and "true" as the filter.
	if _, ok := value.(*influxql.TimeLiteral); ok || name.Val == "time" {
		return m.seriesIDs, &influxql.BooleanLiteral{Val: true}, nil
	}

	// For fields, return all series IDs from this measurement and return
	// the expression passed in, as the filter.
	if name.Val != "_name" && ((name.Type == influxql.Unknown && m.hasField(name.Val)) || name.Type == influxql.AnyField || (name.Type != influxql.Tag && name.Type != influxql.Unknown)) {
		return m.seriesIDs, n, nil
	} else if value, ok := value.(*influxql.VarRef); ok {
		// Check if the RHS is a variable and if it is a field.
		if value.Val != "_name" && ((value.Type == influxql.Unknown && m.hasField(value.Val)) || name.Type == influxql.AnyField || (value.Type != influxql.Tag && value.Type != influxql.Unknown)) {
			return m.seriesIDs, n, nil
		}
	}

	// Retrieve list of series with this tag key.
	tagVals := m.seriesByTagKeyValue[name.Val]

	// if we're looking for series with a specific tag value
	if str, ok := value.(*influxql.StringLiteral); ok {
		var ids SeriesIDs

		// Special handling for "_name" to match measurement name.
		if name.Val == "_name" {
			if (n.Op == influxql.EQ && str.Val == m.Name) || (n.Op == influxql.NEQ && str.Val != m.Name) {
				return m.seriesIDs, nil, nil
			}
			return nil, nil, nil
		}

		if n.Op == influxql.EQ {
			if str.Val != "" {
				// return series that have a tag of specific value.
				ids = tagVals[str.Val]
			} else {
				// Make a copy of all series ids and mark the ones we need to evict.
				seriesIDs := newEvictSeriesIDs(m.seriesIDs)

				// Go through each slice and mark the values we find as zero so
				// they can be removed later.
				for _, a := range tagVals {
					seriesIDs.mark(a)
				}

				// Make a new slice with only the remaining ids.
				ids = seriesIDs.evict()
			}
		} else if n.Op == influxql.NEQ {
			if str.Val != "" {
				ids = m.seriesIDs.Reject(tagVals[str.Val])
			} else {
				for k := range tagVals {
					ids = append(ids, tagVals[k]...)
				}
				sort.Sort(ids)
			}
		}
		return ids, nil, nil
	}

	// if we're looking for series with a tag value that matches a regex
	if re, ok := value.(*influxql.RegexLiteral); ok {
		var ids SeriesIDs

		// Special handling for "_name" to match measurement name.
		if name.Val == "_name" {
			match := re.Val.MatchString(m.Name)
			if (n.Op == influxql.EQREGEX && match) || (n.Op == influxql.NEQREGEX && !match) {
				return m.seriesIDs, &influxql.BooleanLiteral{Val: true}, nil
			}
			return nil, nil, nil
		}

		// Check if we match the empty string to see if we should include series
		// that are missing the tag.
		empty := re.Val.MatchString("")

		// Gather the series that match the regex. If we should include the empty string,
		// start with the list of all series and reject series that don't match our condition.
		// If we should not include the empty string, include series that match our condition.
		if empty && n.Op == influxql.EQREGEX {
			// See comments above for EQ with a StringLiteral.
			seriesIDs := newEvictSeriesIDs(m.seriesIDs)
			for k := range tagVals {
				if !re.Val.MatchString(k) {
					seriesIDs.mark(tagVals[k])
				}
			}
			ids = seriesIDs.evict()
		} else if empty && n.Op == influxql.NEQREGEX {
			ids = make(SeriesIDs, 0, len(m.seriesIDs))
			for k := range tagVals {
				if !re.Val.MatchString(k) {
					ids = append(ids, tagVals[k]...)
				}
			}
			sort.Sort(ids)
		} else if !empty && n.Op == influxql.EQREGEX {
			ids = make(SeriesIDs, 0, len(m.seriesIDs))
			for k := range tagVals {
				if re.Val.MatchString(k) {
					ids = append(ids, tagVals[k]...)
				}
			}
			sort.Sort(ids)
		} else if !empty && n.Op == influxql.NEQREGEX {
			// See comments above for EQ with a StringLiteral.
			seriesIDs := newEvictSeriesIDs(m.seriesIDs)
			for k := range tagVals {
				if re.Val.MatchString(k) {
					seriesIDs.mark(tagVals[k])
				}
			}
			ids = seriesIDs.evict()
		}
		return ids, nil, nil
	}

	// compare tag values
	if ref, ok := value.(*influxql.VarRef); ok {
		var ids SeriesIDs

		if n.Op == influxql.NEQ {
			ids = m.seriesIDs
		}

		rhsTagVals := m.seriesByTagKeyValue[ref.Val]
		for k := range tagVals {
			tags := tagVals[k].Intersect(rhsTagVals[k])
			if n.Op == influxql.EQ {
				ids = ids.Union(tags)
			} else if n.Op == influxql.NEQ {
				ids = ids.Reject(tags)
			}
		}
		return ids, nil, nil
	}

	if n.Op == influxql.NEQ || n.Op == influxql.NEQREGEX {
		return m.seriesIDs, nil, nil
	}
	return nil, nil, nil
}

// FilterExprs represents a map of series IDs to filter expressions.
type FilterExprs map[uint64]influxql.Expr

// DeleteBoolLiteralTrues deletes all elements whose filter expression is a boolean literal true.
func (fe FilterExprs) DeleteBoolLiteralTrues() {
	for id, expr := range fe {
		if e, ok := expr.(*influxql.BooleanLiteral); ok && e.Val == true {
			delete(fe, id)
		}
	}
}

// Len returns the number of elements.
func (fe FilterExprs) Len() int {
	if fe == nil {
		return 0
	}
	return len(fe)
}

// expandExpr returns a list of expressions expanded by all possible tag
// combinations.
func (m *Measurement) expandExpr(expr influxql.Expr) []tagSetExpr {
	// Retrieve list of unique values for each tag.
	valuesByTagKey := m.uniqueTagValues(expr)

	// Convert keys to slices.
	keys := make([]string, 0, len(valuesByTagKey))
	for key := range valuesByTagKey {
		keys = append(keys, key)
	}
	sort.Strings(keys)

	// Order uniques by key.
	uniques := make([][]string, len(keys))
	for i, key := range keys {
		uniques[i] = valuesByTagKey[key]
	}

	// Reduce a condition for each combination of tag values.
	return expandExprWithValues(expr, keys, []tagExpr{}, uniques, 0)
}

func expandExprWithValues(expr influxql.Expr, keys []string, tagExprs []tagExpr, uniques [][]string, index int) []tagSetExpr {
	// If we have no more keys left then execute the reduction and return.
	if index == len(keys) {
		// Create a map of tag key/values.
		m := make(map[string]*string, len(keys))
		for i, key := range keys {
			if tagExprs[i].op == influxql.EQ {
				m[key] = &tagExprs[i].values[0]
			} else {
				m[key] = nil
			}
		}

		// TODO: Rewrite full expressions instead of VarRef replacement.

		// Reduce using the current tag key/value set.
		// Ignore it if reduces down to "false".
		e := influxql.Reduce(expr, &tagValuer{tags: m})
		if e, ok := e.(*influxql.BooleanLiteral); ok && e.Val == false {
			return nil
		}

		return []tagSetExpr{{values: copyTagExprs(tagExprs), expr: e}}
	}

	// Otherwise expand for each possible equality value of the key.
	var exprs []tagSetExpr
	for _, v := range uniques[index] {
		exprs = append(exprs, expandExprWithValues(expr, keys, append(tagExprs, tagExpr{keys[index], []string{v}, influxql.EQ}), uniques, index+1)...)
	}
	exprs = append(exprs, expandExprWithValues(expr, keys, append(tagExprs, tagExpr{keys[index], uniques[index], influxql.NEQ}), uniques, index+1)...)

	return exprs
}

// tagKeysByExpr extracts the tag keys wanted by the expression.
func (m *Measurement) TagKeysByExpr(expr influxql.Expr) (stringSet, bool, error) {
	switch e := expr.(type) {
	case *influxql.BinaryExpr:
		switch e.Op {
		case influxql.EQ, influxql.NEQ, influxql.EQREGEX, influxql.NEQREGEX:
			tag, ok := e.LHS.(*influxql.VarRef)
			if !ok {
				return nil, false, fmt.Errorf("left side of '%s' must be a tag key", e.Op.String())
			}

			if tag.Val != "_tagKey" {
				return nil, false, nil
			}

			tf := TagFilter{
				Op: e.Op,
			}

			if influxql.IsRegexOp(e.Op) {
				re, ok := e.RHS.(*influxql.RegexLiteral)
				if !ok {
					return nil, false, fmt.Errorf("right side of '%s' must be a regular expression", e.Op.String())
				}
				tf.Regex = re.Val
			} else {
				s, ok := e.RHS.(*influxql.StringLiteral)
				if !ok {
					return nil, false, fmt.Errorf("right side of '%s' must be a tag value string", e.Op.String())
				}
				tf.Value = s.Val
			}
			return m.tagKeysByFilter(tf.Op, tf.Value, tf.Regex), true, nil
		case influxql.AND, influxql.OR:
			lhsKeys, lhsOk, err := m.TagKeysByExpr(e.LHS)
			if err != nil {
				return nil, false, err
			}

			rhsKeys, rhsOk, err := m.TagKeysByExpr(e.RHS)
			if err != nil {
				return nil, false, err
			}

			if lhsOk && rhsOk {
				if e.Op == influxql.OR {
					return lhsKeys.union(rhsKeys), true, nil
				}

				return lhsKeys.intersect(rhsKeys), true, nil
			} else if lhsOk {
				return lhsKeys, true, nil
			} else if rhsOk {
				return rhsKeys, true, nil
			}
			return nil, false, nil
		default:
			return nil, false, fmt.Errorf("invalid operator")
		}
	case *influxql.ParenExpr:
		return m.TagKeysByExpr(e.Expr)
	}
	return nil, false, fmt.Errorf("%#v", expr)
}

// tagKeysByFilter will filter the tag keys for the measurement.
func (m *Measurement) tagKeysByFilter(op influxql.Token, val string, regex *regexp.Regexp) stringSet {
	ss := newStringSet()
	for _, key := range m.TagKeys() {
		var matched bool
		switch op {
		case influxql.EQ:
			matched = key == val
		case influxql.NEQ:
			matched = key != val
		case influxql.EQREGEX:
			matched = regex.MatchString(key)
		case influxql.NEQREGEX:
			matched = !regex.MatchString(key)
		}

		if !matched {
			continue
		}
		ss.add(key)
	}
	return ss
}

// tagValuer is used during expression expansion to evaluate all sets of tag values.
type tagValuer struct {
	tags map[string]*string
}

// Value returns the string value of a tag and true if it's listed in the tagset.
func (v *tagValuer) Value(name string) (interface{}, bool) {
	if value, ok := v.tags[name]; ok {
		if value == nil {
			return nil, true
		}
		return *value, true
	}
	return nil, false
}

// tagSetExpr represents a set of tag keys/values and associated expression.
type tagSetExpr struct {
	values []tagExpr
	expr   influxql.Expr
}

// tagExpr represents one or more values assigned to a given tag.
type tagExpr struct {
	key    string
	values []string
	op     influxql.Token // EQ or NEQ
}

func copyTagExprs(a []tagExpr) []tagExpr {
	other := make([]tagExpr, len(a))
	copy(other, a)
	return other
}

// uniqueTagValues returns a list of unique tag values used in an expression.
func (m *Measurement) uniqueTagValues(expr influxql.Expr) map[string][]string {
	// Track unique value per tag.
	tags := make(map[string]map[string]struct{})

	// Find all tag values referenced in the expression.
	influxql.WalkFunc(expr, func(n influxql.Node) {
		switch n := n.(type) {
		case *influxql.BinaryExpr:
			// Ignore operators that are not equality.
			if n.Op != influxql.EQ {
				return
			}

			// Extract ref and string literal.
			var key, value string
			switch lhs := n.LHS.(type) {
			case *influxql.VarRef:
				if rhs, ok := n.RHS.(*influxql.StringLiteral); ok {
					key, value = lhs.Val, rhs.Val
				}
			case *influxql.StringLiteral:
				if rhs, ok := n.RHS.(*influxql.VarRef); ok {
					key, value = rhs.Val, lhs.Val
				}
			}
			if key == "" {
				return
			}

			// Add value to set.
			if tags[key] == nil {
				tags[key] = make(map[string]struct{})
			}
			tags[key][value] = struct{}{}
		}
	})

	// Convert to map of slices.
	out := make(map[string][]string)
	for k, values := range tags {
		out[k] = make([]string, 0, len(values))
		for v := range values {
			out[k] = append(out[k], v)
		}
		sort.Strings(out[k])
	}
	return out
}

// Measurements represents a set of *Measurement.
type Measurements []*Measurement

// Len implements sort.Interface.
func (a Measurements) Len() int { return len(a) }

// Less implements sort.Interface.
func (a Measurements) Less(i, j int) bool { return a[i].Name < a[j].Name }

// Swap implements sort.Interface.
func (a Measurements) Swap(i, j int) { a[i], a[j] = a[j], a[i] }

func (a Measurements) Intersect(other Measurements) Measurements {
	l := a
	r := other

	// we want to iterate through the shortest one and stop
	if len(other) < len(a) {
		l = other
		r = a
	}

	// they're in sorted order so advance the counter as needed.
	// That is, don't run comparisons against lower values that we've already passed
	var i, j int

	result := make(Measurements, 0, len(l))
	for i < len(l) && j < len(r) {
		if l[i].Name == r[j].Name {
			result = append(result, l[i])
			i++
			j++
		} else if l[i].Name < r[j].Name {
			i++
		} else {
			j++
		}
	}

	return result
}

func (a Measurements) Union(other Measurements) Measurements {
	result := make(Measurements, 0, len(a)+len(other))
	var i, j int
	for i < len(a) && j < len(other) {
		if a[i].Name == other[j].Name {
			result = append(result, a[i])
			i++
			j++
		} else if a[i].Name < other[j].Name {
			result = append(result, a[i])
			i++
		} else {
			result = append(result, other[j])
			j++
		}
	}

	// now append the remainder
	if i < len(a) {
		result = append(result, a[i:]...)
	} else if j < len(other) {
		result = append(result, other[j:]...)
	}

	return result
}

// Series belong to a Measurement and represent unique time series in a database.
type Series struct {
	mu          sync.RWMutex
	Key         string
	Tags        models.Tags
	ID          uint64
	measurement *Measurement
}

// NewSeries returns an initialized series struct
func NewSeries(key []byte, tags models.Tags) *Series {
	return &Series{
		Key:  string(key),
		Tags: tags,
	}
}

// Dereference removes references to a byte slice.
func (s *Series) Dereference(b []byte) {
	s.mu.Lock()

	min := uintptr(unsafe.Pointer(&b[0]))
	max := min + uintptr(len(b))

	for i := range s.Tags {
		deref(&s.Tags[i].Key, min, max)
		deref(&s.Tags[i].Value, min, max)
	}

	s.mu.Unlock()
}

func deref(v *[]byte, min, max uintptr) {
	vv := *v

	// Ignore if value is not within range.
	ptr := uintptr(unsafe.Pointer(&vv[0]))
	if ptr < min || ptr > max {
		return
	}

	// Otherwise copy to the heap.
	buf := make([]byte, len(vv))
	copy(buf, vv)
	*v = buf
}

// MarshalBinary encodes the object to a binary format.
func (s *Series) MarshalBinary() ([]byte, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	var pb internal.Series
	pb.Key = &s.Key
	for _, t := range s.Tags {
		pb.Tags = append(pb.Tags, &internal.Tag{Key: proto.String(string(t.Key)), Value: proto.String(string(t.Value))})
	}
	return proto.Marshal(&pb)
}

// UnmarshalBinary decodes the object from a binary format.
func (s *Series) UnmarshalBinary(buf []byte) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	var pb internal.Series
	if err := proto.Unmarshal(buf, &pb); err != nil {
		return err
	}
	s.Key = pb.GetKey()
	s.Tags = make(models.Tags, len(pb.Tags))
	for i, t := range pb.Tags {
		s.Tags[i] = models.Tag{Key: []byte(t.GetKey()), Value: []byte(t.GetValue())}
	}
	return nil
}

// SeriesIDs is a convenience type for sorting, checking equality, and doing
// union and intersection of collections of series ids.
type SeriesIDs []uint64

// Len implements sort.Interface.
func (a SeriesIDs) Len() int { return len(a) }

// Less implements sort.Interface.
func (a SeriesIDs) Less(i, j int) bool { return a[i] < a[j] }

// Swap implements sort.Interface.
func (a SeriesIDs) Swap(i, j int) { a[i], a[j] = a[j], a[i] }

// Equals assumes that both are sorted.
func (a SeriesIDs) Equals(other SeriesIDs) bool {
	if len(a) != len(other) {
		return false
	}
	for i, s := range other {
		if a[i] != s {
			return false
		}
	}
	return true
}

// Intersect returns a new collection of series ids in sorted order that is the intersection of the two.
// The two collections must already be sorted.
func (a SeriesIDs) Intersect(other SeriesIDs) SeriesIDs {
	l := a
	r := other

	// we want to iterate through the shortest one and stop
	if len(other) < len(a) {
		l = other
		r = a
	}

	// they're in sorted order so advance the counter as needed.
	// That is, don't run comparisons against lower values that we've already passed
	var i, j int

	ids := make([]uint64, 0, len(l))
	for i < len(l) && j < len(r) {
		if l[i] == r[j] {
			ids = append(ids, l[i])
			i++
			j++
		} else if l[i] < r[j] {
			i++
		} else {
			j++
		}
	}

	return SeriesIDs(ids)
}

// Union returns a new collection of series ids in sorted order that is the union of the two.
// The two collections must already be sorted.
func (a SeriesIDs) Union(other SeriesIDs) SeriesIDs {
	l := a
	r := other
	ids := make([]uint64, 0, len(l)+len(r))
	var i, j int
	for i < len(l) && j < len(r) {
		if l[i] == r[j] {
			ids = append(ids, l[i])
			i++
			j++
		} else if l[i] < r[j] {
			ids = append(ids, l[i])
			i++
		} else {
			ids = append(ids, r[j])
			j++
		}
	}

	// now append the remainder
	if i < len(l) {
		ids = append(ids, l[i:]...)
	} else if j < len(r) {
		ids = append(ids, r[j:]...)
	}

	return ids
}

// Reject returns a new collection of series ids in sorted order with the passed in set removed from the original.
// This is useful for the NOT operator. The two collections must already be sorted.
func (a SeriesIDs) Reject(other SeriesIDs) SeriesIDs {
	l := a
	r := other
	var i, j int

	ids := make([]uint64, 0, len(l))
	for i < len(l) && j < len(r) {
		if l[i] == r[j] {
			i++
			j++
		} else if l[i] < r[j] {
			ids = append(ids, l[i])
			i++
		} else {
			j++
		}
	}

	// Append the remainder
	if i < len(l) {
		ids = append(ids, l[i:]...)
	}

	return SeriesIDs(ids)
}

// seriesID is a series id that may or may not have been evicted from the
// current id list.
type seriesID struct {
	val   uint64
	evict bool
}

// evictSeriesIDs is a slice of SeriesIDs with an extra field to mark if the
// field should be evicted or not.
type evictSeriesIDs struct {
	ids []seriesID
	sz  int
}

// newEvictSeriesIDs copies the ids into a new slice that can be used for
// evicting series from the slice.
func newEvictSeriesIDs(ids []uint64) evictSeriesIDs {
	a := make([]seriesID, len(ids))
	for i, id := range ids {
		a[i].val = id
	}
	return evictSeriesIDs{
		ids: a,
		sz:  len(a),
	}
}

// mark marks all of the ids in the sorted slice to be evicted from the list of
// series ids. If an id to be evicted does not exist, it just gets ignored.
func (a *evictSeriesIDs) mark(ids []uint64) {
	seriesIDs := a.ids
	for _, id := range ids {
		if len(seriesIDs) == 0 {
			break
		}

		// Perform a binary search of the remaining slice if
		// the first element does not match the value we're
		// looking for.
		i := 0
		if seriesIDs[0].val < id {
			i = sort.Search(len(seriesIDs), func(i int) bool {
				return seriesIDs[i].val >= id
			})
		}

		if i >= len(seriesIDs) {
			break
		} else if seriesIDs[i].val == id {
			if !seriesIDs[i].evict {
				seriesIDs[i].evict = true
				a.sz--
			}
			// Skip over this series since it has been evicted and won't be
			// encountered again.
			i++
		}
		seriesIDs = seriesIDs[i:]
	}
}

// evict creates a new slice with only the series that have not been evicted.
func (a *evictSeriesIDs) evict() (ids SeriesIDs) {
	if a.sz == 0 {
		return ids
	}

	// Make a new slice with only the remaining ids.
	ids = make([]uint64, 0, a.sz)
	for _, id := range a.ids {
		if id.evict {
			continue
		}
		ids = append(ids, id.val)
	}
	return ids
}

// TagFilter represents a tag filter when looking up other tags or measurements.
type TagFilter struct {
	Op    influxql.Token
	Key   string
	Value string
	Regex *regexp.Regexp
}

// MarshalTags converts a tag set to bytes for use as a lookup key.
func MarshalTags(tags map[string]string) []byte {
	// Empty maps marshal to empty bytes.
	if len(tags) == 0 {
		return nil
	}

	// Extract keys and determine final size.
	sz := (len(tags) * 2) - 1 // separators
	keys := make([]string, 0, len(tags))
	for k, v := range tags {
		keys = append(keys, k)
		sz += len(k) + len(v)
	}
	sort.Strings(keys)

	// Generate marshaled bytes.
	b := make([]byte, sz)
	buf := b
	for _, k := range keys {
		copy(buf, k)
		buf[len(k)] = '|'
		buf = buf[len(k)+1:]
	}
	for i, k := range keys {
		v := tags[k]
		copy(buf, v)
		if i < len(keys)-1 {
			buf[len(v)] = '|'
			buf = buf[len(v)+1:]
		}
	}
	return b
}

// WalkTagKeys calls fn for each tag key associated with m.  The order of the
// keys is undefined.
func (m *Measurement) WalkTagKeys(fn func(k string)) {
	m.mu.RLock()
	defer m.mu.RUnlock()

	for k := range m.seriesByTagKeyValue {
		fn(k)
	}
}

// TagKeys returns a list of the measurement's tag names, in sorted order.
func (m *Measurement) TagKeys() []string {
	m.mu.RLock()
	keys := make([]string, 0, len(m.seriesByTagKeyValue))
	for k := range m.seriesByTagKeyValue {
		keys = append(keys, k)
	}
	m.mu.RUnlock()
	sort.Strings(keys)
	return keys
}

// TagValues returns all the values for the given tag key, in an arbitrary order.
func (m *Measurement) TagValues(key string) []string {
	m.mu.RLock()
	defer m.mu.RUnlock()
	values := make([]string, 0, len(m.seriesByTagKeyValue[key]))
	for v := range m.seriesByTagKeyValue[key] {
		values = append(values, v)
	}
	return values
}

// SetFieldName adds the field name to the measurement.
func (m *Measurement) SetFieldName(name string) {
	m.mu.RLock()
	if _, ok := m.fieldNames[name]; ok {
		m.mu.RUnlock()
		return
	}
	m.mu.RUnlock()

	m.mu.Lock()
	m.fieldNames[name] = struct{}{}
	m.mu.Unlock()
}

// FieldNames returns a list of the measurement's field names, in an arbitrary order.
func (m *Measurement) FieldNames() []string {
	m.mu.RLock()
	defer m.mu.RUnlock()

	a := make([]string, 0, len(m.fieldNames))
	for n := range m.fieldNames {
		a = append(a, n)
	}
	return a
}

func (m *Measurement) tagValuesByKeyAndSeriesID(tagKeys []string, ids SeriesIDs) map[string]stringSet {
	// If no tag keys were passed, get all tag keys for the measurement.
	if len(tagKeys) == 0 {
		for k := range m.seriesByTagKeyValue {
			tagKeys = append(tagKeys, k)
		}
	}

	// Mapping between tag keys to all existing tag values.
	tagValues := make(map[string]stringSet, 0)

	// Iterate all series to collect tag values.
	for _, id := range ids {
		s, ok := m.seriesByID[id]
		if !ok {
			continue
		}

		// Iterate the tag keys we're interested in and collect values
		// from this series, if they exist.
		for _, tagKey := range tagKeys {
			if tagVal := s.Tags.GetString(tagKey); tagVal != "" {
				if _, ok = tagValues[tagKey]; !ok {
					tagValues[tagKey] = newStringSet()
				}
				tagValues[tagKey].add(tagVal)
			}
		}
	}

	return tagValues
}

func (m *Measurement) SeriesByTagKeyValue(key string) map[string]SeriesIDs {
	m.mu.RLock()
	ret := m.seriesByTagKeyValue[key]
	m.mu.RUnlock()
	return ret
}

// stringSet represents a set of strings.
type stringSet map[string]struct{}

// newStringSet returns an empty stringSet.
func newStringSet() stringSet {
	return make(map[string]struct{})
}

// add adds strings to the set.
func (s stringSet) add(ss ...string) {
	for _, n := range ss {
		s[n] = struct{}{}
	}
}

// contains returns whether the set contains the given string.
func (s stringSet) contains(ss string) bool {
	_, ok := s[ss]
	return ok
}

// list returns the current elements in the set, in sorted order.
func (s stringSet) list() []string {
	l := make([]string, 0, len(s))
	for k := range s {
		l = append(l, k)
	}
	sort.Strings(l)
	return l
}

// union returns the union of this set and another.
func (s stringSet) union(o stringSet) stringSet {
	ns := newStringSet()
	for k := range s {
		ns[k] = struct{}{}
	}
	for k := range o {
		ns[k] = struct{}{}
	}
	return ns
}

// intersect returns the intersection of this set and another.
func (s stringSet) intersect(o stringSet) stringSet {
	shorter, longer := s, o
	if len(longer) < len(shorter) {
		shorter, longer = longer, shorter
	}

	ns := newStringSet()
	for k := range shorter {
		if _, ok := longer[k]; ok {
			ns[k] = struct{}{}
		}
	}
	return ns
}

// filter removes v from a if it exists.  a must be sorted in ascending
// order.
func filter(a []uint64, v uint64) []uint64 {
	// binary search for v
	i := sort.Search(len(a), func(i int) bool { return a[i] >= v })
	if i >= len(a) || a[i] != v {
		return a
	}

	// we found it, so shift the right half down one, overwriting v's position.
	copy(a[i:], a[i+1:])
	return a[:len(a)-1]
}

// MeasurementFromSeriesKey returns the name of the measurement from a key that
// contains a measurement name.
func MeasurementFromSeriesKey(key string) string {
	// Ignoring the error because the func returns "missing fields"
	k, _, _ := models.ParseKey([]byte(key))
	return escape.UnescapeString(k)
}