The note seems oddly reductionist or strawman-indulging. Nothing about MR says you can't use indices. In a sense, MR is really about sharding! It would be int

The note seems oddly reductionist or strawman-indulging. Nothing about MR says you can't use indices. In a sense, MR is really about sharding! It would be interesting to know how often MR (and its line) has been used on datasets, and execution hardware, which didn't suit standard SQL approaches. But it's also fundamentally different targets (again, both data and hardware). You probably shouldn't be doing MR-like approaches on less than dozens of (commodity, local-disk) nodes, and I think that's a pretty extreme tail for standard monolithic SQL...