Transactional Isolation Tests

[darkfrog26]

LightDB utilizes transactions for every operation; however, there is limited test coverage to verify consistent behavior across all stores. It would be highly worthwhile to have test coverage to validate that all stores similarly handle transaction isolation.

[xolve]

Some stores only have atomic write to a single entry e.g. Redis, while some support levels of transactions e.g. ReadCommitted vs Serialized in Postgres. So the tests have to be per DB type being used. Opinion?

[darkfrog26]

That's mostly how it is now. Transactional isolation is dependent on the store, unless the store implementation utilizes the BufferedWritingTransaction mix-in. This can lead to unexpected logical outcomes when you swap out stores, though. It's probably wise to support a setting on those stores of whether to enable transactional isolation through BufferedWritingTransaction or to allow immediate global state.