influxdb/tx.go

package influxdb

import (
	"fmt"
	"math"
	"sort"
	"time"

	"github.com/boltdb/bolt"
	"github.com/influxdb/influxdb/influxql"
)

// tx represents a transaction that spans multiple shard data stores.
// This transaction will open and close all data stores atomically.
type tx struct {
	server *Server
	now    time.Time

	// used by DecodeFields and FieldIDs. Only used in a raw query, which won't let you select from more than one measurement
	measurement *Measurement
	decoder     fieldDecoder
}

// newTx return a new initialized Tx.
func newTx(server *Server) *tx {
	return &tx{
		server: server,
		now:    time.Now(),
	}
}

// SetNow sets the current time for the transaction.
func (tx *tx) SetNow(now time.Time) { tx.now = now }

// CreateMappers will create a set of mappers that need to be run to execute the map phase of a MapReduceJob.
func (tx *tx) CreateMapReduceJobs(stmt *influxql.SelectStatement, tagKeys []string) ([]*influxql.MapReduceJob, error) {
	// Parse the source segments.
	database, policyName, measurement, err := splitIdent(stmt.Source.(*influxql.Measurement).Name)
	if err != nil {
		return nil, err
	}

	// Find database and retention policy.
	db := tx.server.databases[database]
	if db == nil {
		return nil, ErrDatabaseNotFound
	}
	rp := db.policies[policyName]
	if rp == nil {
		return nil, ErrRetentionPolicyNotFound
	}

	// Find measurement.
	m, err := tx.server.measurement(database, measurement)
	if err != nil {
		return nil, err
	}
	if m == nil {
		return nil, ErrMeasurementNotFound
	}

	tx.measurement = m
	tx.decoder = NewFieldCodec(m)

	// Validate the fields and tags asked for exist and keep track of which are in the select vs the where
	var selectFields []*Field
	var whereFields []*Field
	var selectTags []string

	for _, n := range stmt.NamesInSelect() {
		f := m.FieldByName(n)
		if f != nil {
			selectFields = append(selectFields, f)
			continue
		}
		if !m.HasTagKey(n) {
			return nil, fmt.Errorf("unknown field or tag name in select clause: %s", n)
		}
		selectTags = append(selectTags, n)
	}
	for _, n := range stmt.NamesInWhere() {
		if n == "time" {
			continue
		}
		f := m.FieldByName(n)
		if f != nil {
			whereFields = append(whereFields, f)
			continue
		}
		if !m.HasTagKey(n) {
			return nil, fmt.Errorf("unknown field or tag name in where clause: %s", n)
		}
	}

	// Grab time range from statement.
	tmin, tmax := influxql.TimeRange(stmt.Condition)
	if tmax.IsZero() {
		tmax = tx.now
	}
	if tmin.IsZero() {
		tmin = time.Unix(0, 0)
	}

	// Find shard groups within time range.
	var shardGroups []*ShardGroup
	for _, group := range rp.shardGroups {
		if group.Contains(tmin, tmax) {
			shardGroups = append(shardGroups, group)
		}
	}
	if len(shardGroups) == 0 {
		return nil, nil
	}

	// get the sorted unique tag sets for this query.
	tagSets := m.tagSets(stmt, tagKeys)

	jobs := make([]*influxql.MapReduceJob, 0, len(tagSets))
	for _, t := range tagSets {
		// make a job for each tagset
		job := &influxql.MapReduceJob{
			MeasurementName: m.Name,
			TagSet:          t,
			TMin:            tmin.UnixNano(),
			TMax:            tmax.UnixNano(),
		}

		// make a mapper for each shard that must be hit. We may need to hit multiple shards within a shard group
		mappers := make([]influxql.Mapper, 0)

		// create mappers for each shard we need to hit
		for _, sg := range shardGroups {
			if len(sg.Shards) != 1 { // we'll only have more than 1 shard in a group when RF < # servers in cluster
				// TODO: implement distributed queries.
				panic("distributed queries not implemented yet and there are too many shards in this group")
			}

			shard := sg.Shards[0]
			mapper := &LocalMapper{
				seriesIDs:    t.SeriesIDs,
				db:           shard.store,
				job:          job,
				decoder:      NewFieldCodec(m),
				filters:      t.Filters,
				whereFields:  whereFields,
				selectFields: selectFields,
				selectTags:   selectTags,
			}

			mappers = append(mappers, mapper)
		}

		job.Mappers = mappers

		jobs = append(jobs, job)
	}

	// always return them in sorted order so the results from running the jobs are returned in a deterministic order
	sort.Sort(influxql.MapReduceJobs(jobs))
	return jobs, nil
}

// DecodeValues is for use in a raw data query
func (tx *tx) DecodeValues(fieldIDs []uint8, timestamp int64, data []byte) []interface{} {
	vals := make([]interface{}, len(fieldIDs)+1)
	vals[0] = timestamp
	for i, id := range fieldIDs {
		v, _ := tx.decoder.DecodeByID(id, data)
		vals[i+1] = v
	}
	return vals
}

// FieldIDs will take an array of fields and return the id associated with each
func (tx *tx) FieldIDs(fields []*influxql.Field) ([]uint8, error) {
	names := tx.fieldNames(fields)
	ids := make([]uint8, len(names))

	for i, n := range names {
		field := tx.measurement.FieldByName(n)
		if field == nil {
			return nil, ErrFieldNotFound
		}
		ids[i] = field.ID
	}

	return ids, nil
}

// fieldNames returns the referenced database field names from the slice of fields
func (tx *tx) fieldNames(fields []*influxql.Field) []string {
	var a []string
	for _, f := range fields {
		if v, ok := f.Expr.(*influxql.VarRef); ok { // this is a raw query so we handle it differently
			a = append(a, v.Val)
		}
	}
	return a
}

// LocalMapper implements the influxql.Mapper interface for running map tasks over a shard that is local to this server
type LocalMapper struct {
	cursorsEmpty    bool                   // boolean that lets us know if the cursors are empty
	decoder         fieldDecoder           // decoder for the raw data bytes
	tagSet          *influxql.TagSet       // filters to be applied to each series
	filters         []influxql.Expr        // filters for each series
	cursors         []*bolt.Cursor         // bolt cursors for each series id
	seriesIDs       []uint32               // seriesIDs to be read from this shard
	db              *bolt.DB               // bolt store for the shard accessed by this mapper
	txn             *bolt.Tx               // read transactions by shard id
	job             *influxql.MapReduceJob // the MRJob this mapper belongs to
	mapFunc         influxql.MapFunc       // the map func
	fieldID         uint8                  // the field ID associated with the mapFunc curently being run
	fieldName       string                 // the field name associated with the mapFunc currently being run
	keyBuffer       []int64                // the current timestamp key for each cursor
	valueBuffer     [][]byte               // the current value for each cursor
	tmin            int64                  // the min of the current group by interval being iterated over
	tmax            int64                  // the max of the current group by interval being iterated over
	additionalNames []string               // additional field or tag names that might be requested from the map function
	whereFields     []*Field               // field names that occur in the where clause
	selectFields    []*Field               // field names that occur in the select clause
	selectTags      []string               // tag keys that occur in the select clause
	isRaw           bool                   // if the query is a non-aggregate query
}

func (l *LocalMapper) Open() error {
	// Open the data store
	txn, err := l.db.Begin(false)
	if err != nil {
		return err
	}
	l.txn = txn

	// create a bolt cursor for each unique series id
	l.cursors = make([]*bolt.Cursor, len(l.seriesIDs))

	for i, id := range l.seriesIDs {
		b := l.txn.Bucket(u32tob(id))
		if b == nil {
			continue
		}

		l.cursors[i] = b.Cursor()
	}

	return nil
}

func (l *LocalMapper) Close() {
	_ = l.txn.Rollback()
}

// 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
}

// NextInterval will get the time ordered next interval of the given interval size from the mapper. This is a
// forward only operation from the start time passed into Begin. Will return nil when there is no more data to be read.
func (l *LocalMapper) NextInterval(interval int64) (interface{}, error) {
	if l.cursorsEmpty || l.tmin > l.job.TMax {
		return nil, nil
	}

	// Set the upper bound of the interval.
	if interval > 0 {
		l.tmax = l.tmin + interval - 1
	}

	// Execute the map function. This local mapper acts as the iterator
	val := l.mapFunc(l)

	// see if all the cursors are empty
	l.cursorsEmpty = true
	for _, k := range l.keyBuffer {
		if k != 0 {
			l.cursorsEmpty = false
			break
		}
	}

	// Move the interval forward.
	l.tmin += interval

	return val, nil
}

func (l *LocalMapper) Next() (seriesID uint32, timestamp int64, value interface{}) {
	for {
		// find the minimum timestamp
		min := -1
		minKey := int64(math.MaxInt64)
		for i, k := range l.keyBuffer {
			if k != 0 && k <= l.tmax && k < minKey && k >= l.tmin {
				min = i
				minKey = k
			}
		}

		// return if there is no more data in this group by interval
		if min == -1 {
			return 0, 0, nil
		}

		// set the current timestamp and seriesID
		timestamp = l.keyBuffer[min]
		seriesID = l.seriesIDs[min]

		// decode either the value, or values we need. Also filter if necessary
		var value interface{}
		var err error
		if l.isRaw && len(l.selectFields) > 1 {
			fieldsWithNames := l.decoder.DecodeFieldsWithNames(l.valueBuffer[min])
			value = fieldsWithNames

			// if there's a where clause, make sure we don't need to filter this value
			if l.filters[min] != nil {
				if !matchesWhere(l.filters[min], fieldsWithNames) {
					value = nil
				}
			}
		} else {
			value, err = l.decoder.DecodeByID(l.fieldID, l.valueBuffer[min])

			// if there's a where clase, see if we need to filter
			if l.filters[min] != nil {
				// see if the where is only on this field or on one or more other fields. if the latter, we'll have to decode everything
				if len(l.whereFields) == 1 && l.whereFields[0].ID == l.fieldID {
					if !matchesWhere(l.filters[min], map[string]interface{}{l.fieldName: value}) {
						value = nil
					}
				} else { // decode everything
					fieldsWithNames := l.decoder.DecodeFieldsWithNames(l.valueBuffer[min])
					if !matchesWhere(l.filters[min], fieldsWithNames) {
						value = nil
					}
				}
			}
		}

		// advance the cursor
		nextKey, nextVal := l.cursors[min].Next()
		if nextKey == nil {
			l.keyBuffer[min] = 0
		} else {
			l.keyBuffer[min] = int64(btou64(nextKey))
		}
		l.valueBuffer[min] = nextVal

		// if the value didn't match our filter or if we didn't find the field keep iterating
		if err != nil || value == nil {
			continue
		}

		return seriesID, timestamp, value
	}
}

// matchesFilter returns true if the value matches the where clause
func matchesWhere(f influxql.Expr, fields map[string]interface{}) bool {
	if ok, _ := influxql.Eval(f, fields).(bool); !ok {
		return false
	}
	return true
}

// splitIdent splits an identifier into it's database, policy, and measurement parts.
func splitIdent(s string) (db, rp, m string, err error) {
	a, err := influxql.SplitIdent(s)
	if err != nil {
		return "", "", "", err
	} else if len(a) != 3 {
		return "", "", "", fmt.Errorf("invalid ident, expected 3 segments: %q", s)
	}
	return a[0], a[1], a[2], nil
}

type fieldDecoder interface {
	DecodeByID(fieldID uint8, b []byte) (interface{}, error)
	FieldByName(name string) *Field
	DecodeFieldsWithNames(b []byte) map[string]interface{}
}