It is a design problem endemic to database engines and probably file systems. A design requirement for most of the dynamic runtime data structures is that they can be directly paged to storage, either in whole or in part, and be paged from storage in an arbitrarily distant future on different machines with different compilers. In order to make this work, all data types used in pageable data structures must 1) have a size and alignment that is not compiler-dependent so that page types always have a size that is a strict multiple of the I/O page size and 2) not contain any pointers. This precludes vtables.

This has traditionally been managed with CRTP, tagged unions, etc with some scaffolding to make it convenient and compliant with strict aliasing rules. Ideally, almost all of the dynamic polymorphism is pulled up to the level of the page types, an opaque blob of I/O friendly complex data structure, minimizing the amount you have to do. It is also important to note that JIT-ing has replaced many of the use cases for dynamic dispatch e.g. adding user-defined schemas at runtime.

None of which may apply to your use case. Some things inherently require an unfortunate amount of dynamic dispatch.