The code handling rooted $or queries and subplanning was changed for CBR, affecting plan enumeration even for those queries which are handled entirely by multi-planning.

Currently, there is the possibility that a plan chosen on v8.2 is not enumerated, due to the different handling of the internalQueryEnumerationMaxOrSolutions query knobs. This creates a risk of plan quality regressions.

At very least, we should enumerate the same (or a superset of) plans when using the default query knob settings. Additionally, it would be nice to avoid enumerating fewer plans in cases where the user has customized these knobs. If we cannot achieve this then it should be called out in the TSE enablement materials.