Not an answer, but related, I was looking at Memgraph (graph db) query planning for Cypher, which is similar (ish) to what you are asking about:

https://memgraph.com/docs/querying/query-plan

The reason why I was looking was to do query planning for a declarative pattern-finding in atomic structures (hierarchical labelled graphs, I suppose) although I'm slowly realising just how insanely hard it might be to get it to work efficiently!