// Plan creates an execution plan for the given SelectStatement and returns an Executor.
func (q *QueryExecutor) plan(stmt *influxql.SelectStatement, chunkSize int) (Executor, error) {
shards := map[uint64]meta.ShardInfo{} // Shards requiring mappers.
// Replace instances of "now()" with the current time, and check the resultant times.
stmt.Condition = influxql.Reduce(stmt.Condition, &influxql.NowValuer{Now: time.Now().UTC()})
tmin, tmax := influxql.TimeRange(stmt.Condition)
if tmax.IsZero() {
tmax = time.Now()
}
if tmin.IsZero() {
tmin = time.Unix(0, 0)
}
for _, src := range stmt.Sources {
mm, ok := src.(*influxql.Measurement)
if !ok {
return nil, fmt.Errorf("invalid source type: %#v", src)
}
// Build the set of target shards. Using shard IDs as keys ensures each shard ID
// occurs only once.
shardGroups, err := q.MetaStore.ShardGroupsByTimeRange(mm.Database, mm.RetentionPolicy, tmin, tmax)
if err != nil {
return nil, err
}
for _, g := range shardGroups {
for _, sh := range g.Shards {
shards[sh.ID] = sh
}
}
}
// Build the Mappers, one per shard.
mappers := []Mapper{}
for _, sh := range shards {
m, err := q.ShardMapper.CreateMapper(sh, stmt.String(), chunkSize)
if err != nil {
return nil, err
}
if m == nil {
// No data for this shard, skip it.
continue
}
mappers = append(mappers, m)
}
var executor Executor
if len(mappers) > 0 {
// All Mapper are of same type, so check first to determine correct Executor type.
if _, ok := mappers[0].(*RawMapper); ok {
executor = NewRawExecutor(stmt, mappers, chunkSize)
} else {
executor = NewAggregateExecutor(stmt, mappers)
}
} else {
// With no mappers, the Executor type doesn't matter.
executor = NewRawExecutor(stmt, nil, chunkSize)
}
return executor, nil
}