Thank you Julian. I am able to reproduce your findings.
I am curious if the results highlight a bug in Calcite where we should expect 4 to be returned or is this a query that Calcite should not support? Sean > On Jun 2, 2021, at 11:37 AM, Julian Hyde <jhyde.apa...@gmail.com> wrote: > > Here’s a query that would give the wrong answer if you trim: > > select count(*) from ( > select deptno from scott.emp > union > select deptno from scott.dept); > > returns 4. Note that ‘deptno’ is not used. But when I trim it away, > > select count(*) from ( > select 'a' from scott.emp > union > select 'a' from scott.dept); > > returns 1. (I included ‘a’ because SQL doesn’t allow an empty SELECT clause. > It doesn’t affect the reasoning.) > > Julian > > > >> On Jun 2, 2021, at 6:03 AM, Sean Broeder <sbroe...@apache.org> wrote: >> >> Currently the RefFieldTrimmer only trims on a UNION ALL operation. I've >> been experimenting to see if it is also possible to trim on UNION >> DISTINCT. Is there a simple query that demonstrates why this is not >> possible? >> >> Thanks, >> Sean >
