Hello, I am trying to convert IN or EXISTS to SemiJoin based on Calcite. (such as executing tpch-21.sql)However, SemiJoin only supports equi join condition. I also find that SemiJoin extends from EquiJoin.I wondered why does SemiJoin only support equi join condition in Calcite? As we know, "A “semi-join” between two tables returns rows from the first table where one or more matches are found in the second table. The difference between a semi-join and a conventional join is that rows in the first table will be returned at most once. Even if the second table contains two matches for a row in the first table, only one copy of the row will be returned." (ref http://dbspecialists.com/speeding-queries-semi-joins-anti-joins-oracle-evaluates-exists-not-exists-not)
e.g. select * from l where l.a in (select r.c from r where l.b > r.d) According to the definition, the above SQL can be converted to semi-join. There is an equi join condition: l.a = r.c, which can be used as shuffle key on distributed environment. There is a non-equi join conditions: lb. > r.d, so it can not be converted to SemiJoin in Calcite now. Does SemiJoin support equi join condition temporarily? Or is there some reasons we must do as that? thanks a lot, godfreyhe
