In an expression using AGGR, is it more performant to use a join field
or a non join field
I know it's a bad idea to use join fields for display/ reporting but surely it's good to aggregate by an index? or is that not how QV works?
Often it worked to calculate measures over KEY's but they could be have unexpected results. Therefore if it's possible you should avoid it and from a performance point of view aggr-functions could take a lot of ressources especially if they grab the data from many tables. Further see here: When should the Aggr() function NOT be used?.