The metadata can act as a basic form of indexing (or sometimes caching, though Hydra doesn't use metadata to calculate results yet), but it's not an index in the traditional sense. It's used to eliminate stripes and blocks from consideration during a scan.

Columnar is not ideal for a `users` table where you want to select and update specific rows, often in very small, quick transactions (OLTP). You would want to continue to use a traditional (heap) table in that case. That's certainly something you can still do with Hydra, and combining both kinds of tables is considered HTAP, and something that is a unique use case of our product.

To contrast, columnar is best for "fact" tables -- data about something that happened (thus it does not change) that will be analyzed in an aggregate way. Those might be logs, events, transactions, etc.