If I have two single indices to query: select * table a,b where a=1 and b=2
it doesn't work pretty good and I have to create a group index, how is that possible? how does group indices work? Similar to this: select max(timestampField) from myTable group by groupField I have a index by groupField what it means that it should be really fast to make the group and later make a partial map to find in each node the max of the subset of data to merge the final submax and get the final result in a "reduce" task after sending data through network. Is it how does it work? This query it's really slow, I don't know if I created an index by timestampField I would get better performance, but it doesn't too much sense to create a index with a timestampField where there aren't too row with the same value in a table with 250M rows.... Any advice about this query?
