Thanks Dave and Suresh, I was trying to understand this debug skill and try to make it a tool that can engineers can use in the field to check query performance issues related to subquery unnestting. I think in most cases Trafodion does very well to unnest subqueries. I am trying to find out those scenarios that it cannot do unnesting. And hope this tool can help.
I tried this query: explain options 'f' select * from t1 where not exists (select * from t2 where t2.a2 = t1.a1 ); >From some reference document, it was said EXISTS after a NOT, OR will not be >unnest, but I didn't see that behavior. Maybe Trafodion can already optimize >these subqueries. The subquery I tested is correlated, but it doesn't show any warning. I will try to use gdb to do some debugging asap. Ming
