func (s *Store) CreateMapper(shardID uint64, stmt influxql.Statement, chunkSize int) (Mapper, error) {
shard := s.Shard(shardID)
switch stmt := stmt.(type) {
case *influxql.SelectStatement:
if (stmt.IsRawQuery && !stmt.HasDistinct()) || stmt.IsSimpleDerivative() {
m := NewRawMapper(shard, stmt)
m.ChunkSize = chunkSize
return m, nil
}
return NewAggregateMapper(shard, stmt), nil
case *influxql.ShowMeasurementsStatement:
m := NewShowMeasurementsMapper(shard, stmt)
m.ChunkSize = chunkSize
return m, nil
case *influxql.ShowTagKeysStatement:
return NewShowTagKeysMapper(shard, stmt, chunkSize), nil
default:
return nil, fmt.Errorf("can't create mapper for statement type: %T", stmt)
}
}
