Hello, I looked into the rule recently but to be honest I already forgot what it really does.
Expect: B Hope: A Comments: Judging by the name I would expect B, pushing as much as possible from the top project but not altering the filter. In the end it is just a transpose. On the other hand, I would use the rule mostly as an alternative to RelFieldTrimmer (along with other rules) in order to prune out unnecessary columns as early as possible. Thus, I think option A is what I would like. If it works like B then in some cases it could have also the opposite effect of what I would like; fattening the tuples instead of slimming them down. SELECT sal, comm, sal + comm AS remuneration, sal * 0.45 AS incometax, sal * 0.03 AS surchargetax FROM Emp WHERE deptno = 10 SELECT sal, comm, renumeration, incometax, surchargetax FROM ( SELECT sal, comm, sal + comm AS remuneration, sal * 0.45 As incometax, sal * 0.03 AS surchargetax, deptno FROM Emp) WHERE deptno = 10 Best, Stamatis PS. I will go now and check what the rule does :) On Wed, May 27, 2020 at 8:45 PM Julian Hyde <jh...@apache.org> wrote: > As part of https://issues.apache.org/jira/browse/CALCITE-3975, I've > been looking into what ProjectFilterTransposeRule does with > expressions. It's one of our oldest rules, and I thought I knew what > it did. But the rule does not do what I expect. I've like to conduct a > straw poll to see what other people think. > > Consider the following query (a Project on top of a Filter on a Scan). > > SELECT sal + comm AS remuneration > FROM Emp > WHERE deptno = 10 > > After applying ProjectFilterTransposeRule, what result would you > expect? What would the ideal result be? Are there any extreme cases > (large project lists, complex expressions, expensive filter > expressions) where the rule should do something different? > > Please fill out the following: > > Expect: <option A, B or C, or a query> > Hope: <option A, B or C, or a query> > Comments: > > Option A. Push down references to the fields needed by filter and > project expressions > > SELECT sal + comm AS remuneration > FROM ( > SELECT sal, comm, deptno > FROM Emp) > WHERE deptno = 10 > > B. Push down the project expression, and references to the fields > needed by the filter > > SELECT remuneration > FROM ( > SELECT sal + comm AS remuneration, deptno > FROM Emp) > WHERE deptno = 10 > > C. Push down the project and filter expressions > > SELECT remuneration > FROM ( > SELECT sal + comm AS remuneration, deptno = 10 AS predicate > FROM Emp) > WHERE predicate > > Julian >
