Hi all, I wanted to give an update on this topic: I have started working on this, but I would like to have [4812] merged first, since that's a prerequisite.
Thanks, Alex [4812]: https://github.com/apache/polaris/pull/4812 On Tue, Jun 16, 2026 at 5:15 PM Russell Spitzer <[email protected]> wrote: > > I believe the original idea of TreeMapMetastore was that it looked very > similar to FoundationDB from an API perspective, so it served well as a > test system for the original backend being developed at SF. > > I agree that H2 + JDBC makes sense to me now for the project. > > On Tue, Jun 16, 2026 at 10:03 AM Alexandre Dutra <[email protected]> wrote: > > > Hi all, > > > > Thank you for your feedback. > > > > There seems to be a general agreement on the idea of deprecating > > TreeMapMetaStore, coupled with the JDBC + H2 solution for tests. > > > > In most modules, the tests migration won't pose any serious > > challenges, as replacing the metastore is generally just a matter of > > changing the configuration, and making sure the realm is properly > > bootstrapped. > > > > There will be, however, a few tricky situations in polaris-core: a few > > tests rely on the TreeMapMetaStore, mostly as a test convenience; but > > there is no obvious replacement for it in that module. I am however > > confident that we can find a solution for that, either based on mocks, > > or by bringing in a real metastore. > > > > If no objections are raised, I am going to prepare a PR for this. > > > > Thanks, > > Alex > > > > On Tue, Jun 16, 2026 at 3:28 PM Dmitri Bourlatchkov <[email protected]> > > wrote: > > > > > > Hi Alex, > > > > > > Thanks for starting this thread. > > > > > > I also find the TransactionalMetaStoreManagerImpl and related call paths > > > conuising in Apache Polaris code. > > > > > > I support promoting H2 to the default (in memory) Persistence backend for > > > getting started cases. This should also resolve the old H2 evolution > > thread > > > [1] by ensuring it is used regularly on the same code paths as > > PostgreSQL. > > > > > > Deprecating TransactionalMetaStoreManagerImpl for removal also sounds > > > reasonable to me. Existing downstream users > > > of TransactionalMetaStoreManagerImpl will have time to migrate, or even > > > embed that code (per ASF license) into local builds, during the > > deprecation > > > phase. > > > > > > [1] https://lists.apache.org/thread/g1gg2w8hn9gvlmwrdh0x218whoh2wd39 > > > > > > Cheers, > > > Dmitri. > > > > > > On Fri, Jun 12, 2026 at 11:24 AM Alexandre Dutra <[email protected]> > > wrote: > > > > > > > Hi all, > > > > > > > > I am writing to ask the community whether it is OK to deprecate > > > > TreeMapMetaStore, as well as all the in-memory metastore manager, > > > > metastore manager factory, and persistence types that rely solely on > > > > TreeMapMetaStore. > > > > > > > > As we know, these components are test-grade only, and not suitable for > > > > production. They trigger a production readiness alert on Polaris > > > > startup. It's a considerable amount of code that is virtually dead in > > > > production. > > > > > > > > It's also confusing for developers. E.g. the "transactional" metastore > > > > is not transactional in the JDBC sense of the term, and thus not used > > > > by JDBC persistence. It also has its quirks: some return statuses are > > > > only returned by that manager. > > > > > > > > However, these components are used in tests, and I agree that it's > > > > useful to have an in-memory version of the persistence layer for > > > > tests. But we have today two alternatives that are imho superior for > > > > tests in polaris-runtime-service: > > > > > > > > - JDBC persistence with H2 backend. There are already a few tests > > > > using this setup. > > > > - NoSQL persistence with InMemory backend. > > > > > > > > Both alternatives test real production-grade persistence code. > > > > > > > > And finally, TreeMapMetaStore is currently the default runtime > > > > persistence in application.properties; and the Helm chart also > > > > advertises it as the default. These are not sane defaults, imho. It's > > > > always tricky to provide a good default for datastores, but since JDBC > > > > persistence is included by default in the server image, I think that > > > > including the H2 driver by default could give us a saner default while > > > > keeping the out-of-the-box experience intact (the license is Category > > > > A). > > > > > > > > Concretely: > > > > > > > > On the MetaStoreManagerFactory hierarchy, the following > > > > implementations are completely in-memory: > > > > > > > > - InMemoryPolarisMetaStoreManagerFactory: could be removed > > > > > > > > - InMemoryAtomicOperationMetaStoreManagerFactory: could be removed > > > > > > > > - LocalPolarisMetaStoreManagerFactory: is the base class of the two > > > > above; imho it can be removed, but since it's an abstract class, it > > > > may have been extended outside Polaris. But neither JDBC nor NoSQL use > > > > it. > > > > > > > > On the PolarisMetaStoreManager hierarchy: > > > > > > > > - TransactionalMetaStoreManagerImpl: is only used by > > > > LocalPolarisMetaStoreManagerFactory. JDBC and NoSQL do not use it. > > > > Could be removed. > > > > > > > > - TransactionWorkspaceMetaStoreManager however is a different beast, > > > > in spite of the similar name. It is in use today on the commit path, > > > > so should not be removed. > > > > > > > > On the BasePersistence hierarchy: > > > > > > > > - TreeMapTransactionalPersistenceImpl and its TreeMapMetaStore are > > > > only used by InMemoryPolarisMetaStoreManagerFactory, and could be > > > > removed; > > > > > > > > - TransactionalPersistence and AbstractTransactionalPersistence: these > > > > are supertypes of TreeMapTransactionalPersistenceImpl and thus only > > > > used for in-memory. They imo can be removed, but they might have been > > > > extended or implemented outside Polaris. > > > > > > > > I think it's important to keep Polaris code tidy by removing unused, > > > > unimplementable, or test-grade only components. > > > > > > > > What are your thoughts? > > > > > > > > Thanks, > > > > Alex > > > > > >
