Currently, Doris does not support multi-table materialized view. So the mv with join is not supported yet.
Doris only support mv for single table, with some certain aggregation such as sum, min, max, count, count(dinstinct) For example, there is a base table A with column (k1, k2, v1, v2), you can create a mv B like: select k1, sum(v1) from A group by k1. And now, you got a base table A and a mv B. When data is loading into table A, it will generate a copy of data to B. For table A, the loading data is with column (k1, k2,v1,v2), and for mv B, the loading data will be (k1, v1). The aggregation is done on BE side, the BE will receive data (k1, v1) and do the aggregation (k1, sum(v1)). You can see StreamLoadPlanner.java in FE for the query plan, and DeltaWriter.h/cpp in BE for doing the aggregation. -- 此致！Best Regards 陈明雨 Mingyu Chen Email: morning...@apache.org At 2022-09-23 23:29:44, "Botong Huang" <pku...@gmail.com> wrote: >Thanks for the reply! > >I do understand from doc that the incremental update of MV is triggered >upon base table change. > >But I cannot find the actual code in Doris code base that does the update, >specifically the actual incremental plan (tree of operator generated by the >optimizer) to update the view result. > >For example, if the view is "Select * from A inner join B". Then for each >new line in A, it needs to join all rows in B to get the correct updates to >the view. > > Or if the view is "Select avg(score) from A", then I assume the plan for >the update should be something like "Select sum(score), count(score) from >\delta A". > >Thanks, >Botong > >On Fri, Sep 23, 2022 at 9:46 PM Mingyu Chen <morning...@163.com> wrote: > >> It controls by load process. >> After a mv is built, all following load task will generate many copies of >> import data to base table and all materialized views. >> So the incremental update happens on every load task. >> >> >> >> >> -- >> >> 此致！Best Regards >> 陈明雨 Mingyu Chen >> >> Email: >> morning...@apache.org >> >> >> >> >> >> 在 2022-09-21 15:59:17，"Botong Huang" <pku...@gmail.com> 写道： >> >Hi all, >> > >> >Does anyone know where the code is for generating the incremental plan for >> >updating the materialized view when the base table receives new data? Many >> >thanks! >> > >> >想知道物化视图的增量维护的plan生成的代码在哪里，谢谢！ >> > >> >Best, >> >Botong >>
