I think named entity recognition may help if detailed labels were used. The parser can already label the where clause, select clause, etc. However a component o

I think named entity recognition may help if detailed labels were used. The parser can already label the where clause, select clause, etc. However a component of a where clause in a given query may be better executed as a join clause. Given enough training data, NER should be able to recognize the join clause within the where clause in that specific context and the resulting labels would give the optimizer a hint on how to rewrite that specific query. Now I have no idea how much training data you would need or if a single, trained model would work for most use cases. But I think it could work in theory.