Hi Prashant I guess the answer will depend on how easy it should be for Polaris to support multi-tenancy.
A separate database per realm would allow administrators to limit the amount of resources that a realm can consume (e.g. the maximum number of database connections). Indeed, it would be one of the strongest isolation mode. However, the code would need to support a complete database configuration per realm (think username and password and possibly IP address) if the goal is to match Postgres capabilities. In terms of backup/restore, it is the most flexible option. A "one schema per realm" approach would be a simpler approach, regarding datasource configuration. However, there would be less isolation between realms, and a resource utilization spike on one realm could impact performance of another realm. It is as flexible as option #1 regarding backup and restore. A "realm as part of the primary key" approach is the most efficient way, in that the cost of adding tenants is close to zero. Like in option #2, there is no real resource isolation between tenants and a noisy-neighbor situation is a possible issue. The biggest difference is regarding backup and restore. Consider the case where data is accidentally wiped/corrupted/modified/... in a given tenant and administrators want to restore it to a previous state. With this approach, it is a much more complex as Postgres does not (AFAIK) allow the possibility to restore tables partially. Just my 2 cents -- Pierre On Tue, Apr 15, 2025 at 12:42 AM Prashant Singh <prashant.si...@snowflake.com.invalid> wrote: > Dear Polaris Community, > > This email initiates a discussion regarding the modeling of Realms within > the Polaris project, following its recent mention in my JDBC implementation > pull request: > https://github.com/apache/polaris/pull/1287/files#r2040383971. > > My current understanding, based on available information, is that Realms > were primarily intended for isolation. Consequently, the EclipseLink > implementation treats each Realm as a separate database. > > As we are re-implementing this functionality, it was suggested that we > gather community feedback on the optimal approach to modeling Realms. > > Based on my current understanding, here are potential modeling options: > > *1. Separate Databases per Realm:* > > - Each Realm would correspond to a distinct database. > - This could be implemented using Quarkus custom data sources, with one > data source per Realm. > > *2. Separate Schemas per Realm:* > > - Each Realm would correspond to a distinct database schema within a > single database. > - Most database systems support two-part identifiers ( > <schema_name>.<table_name>), allowing for data isolation. > > *3. Realm as a Primary Key:* > > - A realm identifier would be added as a primary key (or part of a > composite primary key) to each Polaris table. > - Data isolation would be enforced through filtering based on this key > during data access. > > The optimal approach will likely depend on ease of use and maintainability > for database administrators. > > Please share your thoughts and preferences regarding these options. > > Best regards, > > Prashant Singh >
