It sounds like a good fit. Parse the SQL, translate to relational algebra, apply some query transformation rules on the algebra.
If you have a few simple transformations in mind, you may be able to achieve it without a cost model. Or, as you propose, a simple model based on cardinality. To convert a union of conjunctive queries to a conjunction of possibly-union queries, you would probably need a rule called UnionJoinTransposeRule that converts (Union (Join X Y) (Join X Y)) into (Join X (Union Y Z)) or something like that, and combines it with some existing rules to push unions. There is currently no such rule but it would not be hard to write. Julian > On Feb 14, 2018, at 5:24 AM, Guohui Xiao <x...@inf.unibz.it> wrote: > > Hi, > > We are considering using Calcite to perform cost-based query optimization > in our project. > > Specifically, we can already generate some SQL queries expressed in some > relational algebra expression through our API, and we want to optimize the > generated expressions using Calcite. > > We have a cost model based on cardinality estimation. We want to use it to > convert e.g., a union of conjunctive queries (UCQ) into a a join of UCQs. > > We would like to understand how much efforts are needed to realize our idea > using Calcite. > > Do you have suggestions about this? > > Thanks in advance. > > Best regards, > > Guohui & Davide > > > > -- > Guohui Xiao, PhD > Assistant Professor with a fixed-term contract > KRDB - Faculty of Computer Science > Free University of Bozen-Bolzano > Piazza Domenicani, 3 > I-39100 Bolzano, Italy > > http://www.ghxiao.org
