I have a 150,000-record free table with a 239-char field called cPath. First I did a "index on cPath tag cPath". Doing a "set order to" and then "select cPath from mytable distinct" takes 82.58 seconds. Then I tried "select cPath from mytable group by cPath" and it took 67.90 seconds.

Why am I not getting subsecond response? What's the best wat to optimize this query? Thanks.