been doing a lot of pgsql/mysql performance testing lately, and there is one query that mysql does much better than pgsql...and I see it a lot in normal development: select a,b,max(c) from t group by a,b; t has an index on a,b,c. in my sample case with cardinality of 1000 for a, 2000 for b, and 300000 records in t, pgsql does a seq. scan on dev box in about a second (returning 2000 records). recent versions of mysql do much better, returning same set in < 20ms. mysql explain says it uses an index to optimize the group by somehow. is there a faster way to write this query? Merlin
