What's the relationship between Ignite and H2? My sense is that H2 creates, updates, and queries indexes built on cached values, while Ignite handles actual data storage (e.g. cache, vs records in a data file) and distributing queries and gathering results to/from cache nodes. Thus, H2 isn't actually storing the data anywhere (outside of cache), just managing indexes?
Your understanding is correct. H2 is mostly used for query parsing and execution planning. Indexes and tables are highly customized to work directly with the data stored in cache and to provide better performance in highly concurrent scenarios.