If you compare the two, then you must compare apples with apples. That is, you must compare relational DBs where every column is indexed since with column-orien

If you compare the two, then you must compare apples with apples. That is, you must compare relational DBs where every column is indexed since with column-oriented DBs, you can search by arbitrary columns without having to worry about which column is indexed. You can say that in practice you don't need this, so you reduce functionality but you're no longer comparing apples to apples. Besides, it's nice to search by any column, just because relational DBs limit you doesn't mean it's not useful. map-reduce databases are something entirely different, although you can do map-reduce via joins if need be. You denormalize because, among other things, you don't have complex joins. With column-oriented DBs that can perform joins, denormalization is not necessary. NoSql is something entirely different.