// 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...
func (m *Measurement) tagSets(stmt *influxql.SelectStatement, dimensions []string) map[string]map[uint32]influxql.Expr {
// get the unique set of series ids and the filters that should be applied to each
seriesIDs, filters := m.seriesIDsAndFilters(stmt)
// build the tag sets
tagSets := make(map[string]map[uint32]influxql.Expr)
for _, id := range seriesIDs {
// get the series and set the tag values for the dimensions we care about
s := m.seriesByID[id]
tags := make([]string, len(dimensions))
for i, dim := range dimensions {
tags[i] = s.Tags[dim]
}
// marshal it into a string and put this series and its expr into the tagSets map
t := string(influxql.MarshalStrings(tags))
set, ok := tagSets[t]
if !ok {
set = make(map[uint32]influxql.Expr)
}
set[id] = filters[id]
tagSets[t] = set
}
return tagSets
}
// NewIterator returns a new iterator.
func NewIterator(tags []string, points []Point) *Iterator {
return &Iterator{tags: string(influxql.MarshalStrings(tags)), points: points}
}