mapsideJoinStrategy.create() use LoadLeftSideMapsideJoinStrategy, i'm just confused why LoadLeftSideMapsideJoinStrategy is better than default strategy.
according to the annotation, LoadLeftSideMapsideJoinStrategy peforms better than default strategy, but i don't know why 2016-05-10 11:30 GMT+08:00 David Ortiz <[email protected]>: > Try mapsideJoinStrategy.create() > > On Mon, May 9, 2016, 9:29 PM 陈竞 <[email protected]> wrote: > >> hi, i'm very confused when i use MapsideJoinStrategy. the origin >> constructor was deprecated, instead, LoadLeftSideMapsideJoinStrategy was >> recommended, the main improvement is that load left side table in memory, >> whose size is large than right side. however, when i want to use mas side >> join, the left side table usually is too large to store in memory. >> >> for example i have to table A and B, we need A left join B, and >> size(A)>>size(B), naturally we want to use map side join, and use A as left >> side, B as right side, then load B in memory to process, it's very simple. >> However, if we use LoadLeftSideMapsideJoinStrategy, we use A as right side, >> B as left side, which makes no improvement while adding a reverse DoFn >> >> >> >> -- >> 陈竞，中科院计算技术研究所，高性能计算机中心 >> Jing Chen HPCC.ICT.AC China >> > -- 陈竞，中科院计算技术研究所，高性能计算机中心 Jing Chen HPCC.ICT.AC China
