// Open opens the raw mapper.
func (rm *RawMapper) Open() error {
// Get a read-only transaction.
tx, err := rm.shard.DB().Begin(false)
if err != nil {
return err
}
rm.tx = tx
// Set all time-related parameters on the mapper.
rm.queryTMin, rm.queryTMax = influxql.TimeRangeAsEpochNano(rm.stmt.Condition)
// Create the TagSet cursors for the Mapper.
for _, src := range rm.stmt.Sources {
mm, ok := src.(*influxql.Measurement)
if !ok {
return fmt.Errorf("invalid source type: %#v", src)
}
m := rm.shard.index.Measurement(mm.Name)
if m == nil {
// This shard have never received data for the measurement. No Mapper
// required.
return nil
}
// Create tagset cursors and determine various field types within SELECT statement.
tsf, err := createTagSetsAndFields(m, rm.stmt)
if err != nil {
return err
}
tagSets := tsf.tagSets
rm.selectFields = tsf.selectFields
rm.selectTags = tsf.selectTags
rm.whereFields = tsf.whereFields
if len(rm.selectFields) == 0 {
return fmt.Errorf("select statement must include at least one field")
}
// SLIMIT and SOFFSET the unique series
if rm.stmt.SLimit > 0 || rm.stmt.SOffset > 0 {
if rm.stmt.SOffset > len(tagSets) {
tagSets = nil
} else {
if rm.stmt.SOffset+rm.stmt.SLimit > len(tagSets) {
rm.stmt.SLimit = len(tagSets) - rm.stmt.SOffset
}
tagSets = tagSets[rm.stmt.SOffset : rm.stmt.SOffset+rm.stmt.SLimit]
}
}
// Create all cursors for reading the data from this shard.
for _, t := range tagSets {
cursors := []*seriesCursor{}
for i, key := range t.SeriesKeys {
c := createCursorForSeries(rm.tx, rm.shard, key)
if c == nil {
// No data exists for this key.
continue
}
cm := newSeriesCursor(c, t.Filters[i])
cursors = append(cursors, cm)
}
tsc := newTagSetCursor(m.Name, t.Tags, cursors, rm.shard.FieldCodec(m.Name))
// Prime the buffers.
for i := 0; i < len(tsc.cursors); i++ {
k, v := tsc.cursors[i].SeekTo(rm.queryTMin)
tsc.keyBuffer[i] = k
tsc.valueBuffer[i] = v
}
rm.cursors = append(rm.cursors, tsc)
}
sort.Sort(tagSetCursors(rm.cursors))
}
return nil
}
// Open opens the aggregate mapper.
func (am *AggMapper) Open() error {
var err error
// Get a read-only transaction.
tx, err := am.shard.DB().Begin(false)
if err != nil {
return err
}
am.tx = tx
// Set up each mapping function for this statement.
aggregates := am.stmt.FunctionCalls()
am.mapFuncs = make([]influxql.MapFunc, len(aggregates))
am.fieldNames = make([]string, len(am.mapFuncs))
for i, c := range aggregates {
am.mapFuncs[i], err = influxql.InitializeMapFunc(c)
if err != nil {
return err
}
// 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:
am.fieldNames[i] = lit.Val
case *influxql.Distinct:
if c.Name != "count" {
return fmt.Errorf("aggregate call didn't contain a field %s", c.String())
}
am.fieldNames[i] = lit.Val
default:
return fmt.Errorf("aggregate call didn't contain a field %s", c.String())
}
}
// Set all time-related parameters on the mapper.
am.queryTMin, am.queryTMax = influxql.TimeRangeAsEpochNano(am.stmt.Condition)
// For GROUP BY time queries, limit the number of data points returned by the limit and offset
d, err := am.stmt.GroupByInterval()
if err != nil {
return err
}
am.intervalSize = d.Nanoseconds()
if am.queryTMin == 0 || am.intervalSize == 0 {
am.numIntervals = 1
am.intervalSize = am.queryTMax - am.queryTMin
} else {
intervalTop := am.queryTMax/am.intervalSize*am.intervalSize + am.intervalSize
intervalBottom := am.queryTMin / am.intervalSize * am.intervalSize
am.numIntervals = int((intervalTop - intervalBottom) / am.intervalSize)
}
if am.stmt.Limit > 0 || am.stmt.Offset > 0 {
// ensure that the offset isn't higher than the number of points we'd get
if am.stmt.Offset > am.numIntervals {
return nil
}
// Take the lesser of either the pre computed number of GROUP BY buckets that
// will be in the result or the limit passed in by the user
if am.stmt.Limit < am.numIntervals {
am.numIntervals = am.stmt.Limit
}
}
// If we are exceeding our MaxGroupByPoints error out
if am.numIntervals > MaxGroupByPoints {
return errors.New("too many points in the group by interval. maybe you forgot to specify a where time clause?")
}
// Ensure that the start time for the results is on the start of the window.
am.queryTMinWindow = am.queryTMin
if am.intervalSize > 0 && am.numIntervals > 1 {
am.queryTMinWindow = am.queryTMinWindow / am.intervalSize * am.intervalSize
}
// Create the TagSet cursors for the Mapper.
for _, src := range am.stmt.Sources {
mm, ok := src.(*influxql.Measurement)
if !ok {
return fmt.Errorf("invalid source type: %#v", src)
}
m := am.shard.index.Measurement(mm.Name)
if m == nil {
// This shard have never received data for the measurement. No Mapper
// required.
return nil
}
// Create tagset cursors and determine various field types within SELECT statement.
tsf, err := createTagSetsAndFields(m, am.stmt)
if err != nil {
return err
}
tagSets := tsf.tagSets
am.selectFields = tsf.selectFields
am.selectTags = tsf.selectTags
am.whereFields = tsf.whereFields
// Validate that group by is not a field
if err := m.ValidateGroupBy(am.stmt); err != nil {
return err
}
// SLIMIT and SOFFSET the unique series
if am.stmt.SLimit > 0 || am.stmt.SOffset > 0 {
if am.stmt.SOffset > len(tagSets) {
tagSets = nil
} else {
if am.stmt.SOffset+am.stmt.SLimit > len(tagSets) {
am.stmt.SLimit = len(tagSets) - am.stmt.SOffset
}
tagSets = tagSets[am.stmt.SOffset : am.stmt.SOffset+am.stmt.SLimit]
}
}
// Create all cursors for reading the data from this shard.
for _, t := range tagSets {
cursors := []*seriesCursor{}
for i, key := range t.SeriesKeys {
c := createCursorForSeries(am.tx, am.shard, key)
if c == nil {
// No data exists for this key.
continue
}
cm := newSeriesCursor(c, t.Filters[i])
cursors = append(cursors, cm)
}
tsc := newTagSetCursor(m.Name, t.Tags, cursors, am.shard.FieldCodec(m.Name))
am.cursors = append(am.cursors, tsc)
}
sort.Sort(tagSetCursors(am.cursors))
}
return nil
}