Do id columns help (in speed) select statements?
Since you mentioned your typical queries involve grouping by string fields, I assume you have many duplicate values in these columns (otherwise grouping makes no sense). 

You can definitely improve performance by creating lookup table[s] for values stored in someData1, someData2, someData3 with integer primary key and changing original someData1 to someData1_id . You still need index on someData1_id, but taking into account number of rows , the new index will be much smaller than index on string field, and as a result , much faster...