Hi Alex, Thanks for summarizing the discussion and separating the two questions. I think that helps move us toward consensus.
First of all, I agree with the direction, but I'm not sure it's urgent. TreeMapMetaStore isn't perfect, but we already have both JDBC + H2 and NoSQL + in-memory in place. That should already satisfy most of test coverage. For question 1, I'd prefer Option 1a (JDBC + H2). My main reason is that it exercises the same persistence layer, transaction handling, schema management, and configuration that most production deployments use. That gives us a better out of the box experience for both users and developers, while also increasing confidence that what works locally will behave similarly in production. Do we have to wait for either PR 4812 or 4984? I think bundling the H2 driver should just unblock 1a. For question 2, I agree with handling test migration on a case by case basis. Different tests have different goals, and using the most appropriate backend for each test seems reasonable. Thanks, Yufei On Fri, Jul 17, 2026 at 10:45 AM Dmitri Bourlatchkov <[email protected]> wrote: > Hi Alex, > > Option 1b certainly makes sense to me. I support going in that direction. > > I'd propose opening a PR for that merging it before proceeding to test code > changes. > > In general, if 1b is acceptable, I'd think H2 should be removed [1] from > tests and replaced with PostgreSQL or NoSQL InMemory. With that in mind, > updating tests on a case-by-case basis seems reasonable to me. We can > decide separately in each PR. > > [1] https://lists.apache.org/thread/g1gg2w8hn9gvlmwrdh0x218whoh2wd39 > > Cheers, > Dmitri. > > > On Fri, Jul 17, 2026 at 12:59 PM Alexandre Dutra <[email protected]> > wrote: > > > Hi Dmitri, hi all, > > > > Unfortunately I'm not sure your interpretation matches mine, so let's > > try to wrap up this discussion methodically. > > > > We agreed to deprecate TreeMapMetaStore for removal. But we haven't > > reached consensus on two questions: > > > > 1) What should be the default metastore in the server image? > > 2) How to replace TreeMapMetaStore in tests? > > > > Question 1) is tricky and needs a clear decision. We have only two > > options for a smooth UX (aka, "docker run apache/polaris" just works): > > > > - Option 1a: JDBC+H2 > > - Option 1b: NoSQL+InMemory > > > > Option 1a is hard because it requires either my work on [4812] > > (runtime activated datasources) or Yufei's work on [4984] (unmanaged > > datasources). It also *requires* the H2 driver to be bundled by > > default, which some people are not comfortable with. In short, I don't > > see this option being feasible any time soon. > > > > Therefore, I think option 1b is much easier, and that would be my > > preference. > > > > Question 2) is not as urgent, as I'm fairly sure we can find a > > solution as we go. I can see a few options: > > - Option 2a: migrate to JDBC+H2 > > - Option 2b: migrate to NoSQL+InMemory > > - Option 2c: decide on a case-by-case basis > > > > My personal preference would be 2c. > > > > Can we try to reach consensus on the two questions please? > > > > Thanks, > > Alex > > > > [4812]: https://github.com/apache/polaris/pull/4812 > > [4984]: https://github.com/apache/polaris/pull/4984 > > > > On Mon, Jul 6, 2026 at 8:29 PM Dmitri Bourlatchkov <[email protected]> > > wrote: > > > > > > Hi All, > > > > > > My interpretation of the discussion so far is that: > > > > > > 1) We do want to deprecate the TreeMap MetaStore for removal > > > > > > 2) JDBC + PostgreSQL should be used for testing as well as NoSQL + > > MongoDB > > > (I believe it is in fact the case in current CI). > > > > > > 3) Instead of the TreeMap MetaStore, we will use the in-memory NoSQL > > > MetaStore (for lightweight tests) > > > > > > Now, H2 becomes irrevant, IMHO, but removing it is being discussed > > > separately [1]. > > > > > > How does that sound? > > > > > > [1] https://lists.apache.org/thread/g1gg2w8hn9gvlmwrdh0x218whoh2wd39 > > > > > > Thanks, > > > Dmitri. > > > > > > On Fri, Jul 3, 2026 at 5:25 AM Alexandre Dutra <[email protected]> > > wrote: > > > > > > > Hi all, > > > > > > > > I'm confused: security concerns were previously raised here [1] and > > > > here [2] about bundling the H2 driver due to its past record of > > > > critical CVEs. > > > > > > > > As a result, I assumed the JDBC+H2 option had been abandoned. Has > this > > > > proposal been brought back into consideration? > > > > > > > > Thanks, > > > > Alex > > > > > > > > [1]: > https://lists.apache.org/thread/jq41dpqoys551wf30qkf0wcwxssxo3qj > > > > [2]: > https://lists.apache.org/thread/qdzb3lt8fwbpkjyd3lh07ylxr6wpwn1r > > > > > > > > > > > > On Fri, Jul 3, 2026 at 8:54 AM Jean-Baptiste Onofré <[email protected] > > > > > > wrote: > > > > > > > > > > Hi > > > > > > > > > > Yeah fully agree and it was my point when I replied on the thread > > > > > initially. > > > > > > > > > > Regards > > > > > JB > > > > > > > > > > Le jeu. 2 juil. 2026 à 23:32, Yufei Gu <[email protected]> a > > écrit : > > > > > > > > > > > If our goal is to make the default experience closer to > production > > > > > > while removing TreeMap, then JDBC with H2 seems like a more > natural > > > > > > choice. It exercises the same persistence layer, schema > management, > > > > > > and configuration that users will encounter in production, while > > still > > > > > > keeping setup lightweight. > > > > > > > > > > > > Yufei > > > > > > > > > > > > Yufei > > > > > > > > > > > > > > > > > > On Thu, Jul 2, 2026 at 3:46 AM Alexandre Dutra < > [email protected]> > > > > wrote: > > > > > > > > > > > > > > Hi Russell, > > > > > > > > > > > > > > The existing default metastore shouldn't be viewed merely as a > > > > > > > "relatively simple, self-contained implementation": it has > unique > > > > > > > quirks, such as returning result types that no other metastore > > does. > > > > > > > > > > > > > > Choosing the status quo simply to avoid making changes is imho > > the > > > > > > > worst solution. > > > > > > > > > > > > > > Transitioning to the NoSQL metastore as the default remains a > net > > > > > > > benefit, even if it is only used by 30% of the user base. > > > > > > > > > > > > > > However, I agree with keeping the test suite on JDBC + H2 by > > default > > > > > > > if that ensures a higher level of confidence in our tests > > ability to > > > > > > > reproduce real production setups. > > > > > > > > > > > > > > Thanks, > > > > > > > Alex > > > > > > > > > > > > > > On Wed, Jul 1, 2026 at 12:23 AM Russell Spitzer > > > > > > > <[email protected]> wrote: > > > > > > > > > > > > > > > > I agree TreeMap and its associated transactional stack should > > be > > > > > > deprecated. > > > > > > > > It’s test-only, confusing, and not used by JDBC production > > paths. > > > > > > > > > > > > > > > > I’m less convinced that NoSQL + InMemory is a clearly > superior > > > > > > replacement > > > > > > > > for TreeMap in tests. At the storage layer it’s essentially > the > > > > same > > > > > > class > > > > > > > > of > > > > > > > > thing: an in-memory, non-durable backend. The difference is > > that > > > > it > > > > > > > > exercises > > > > > > > > a completely different MetaStoreManager/persistence stack > > > > > > > > (NoSqlMetaStoreManager > > > > > > > > vs TransactionalMetaStoreManagerImpl), not the JDBC path most > > > > > > deployments > > > > > > > > use. It > > > > > > > > replaces a relatively simple, self-contained implementation > > with > > > > > > something > > > > > > > > that is > > > > > > > > part of a much more complicated persistence stack, while > > remaining > > > > > > > > non-durable > > > > > > > > and test-only at the storage layer. > > > > > > > > > > > > > > > > For the problems originally raised (test-grade defaults, dead > > > > > > production > > > > > > > > path, developer confusion), > > > > > > > > JDBC + H2 seems like an actual fix. > > > > > > > > > > > > > > > > > > > > > > > > On Mon, Jun 29, 2026 at 2:06 PM Dmitri Bourlatchkov < > > > > [email protected]> > > > > > > > > wrote: > > > > > > > > > > > > > > > > > Hi Alex, > > > > > > > > > > > > > > > > > > I tend to agree that the DataSource discussion related to > H2 > > > > became > > > > > > a bit > > > > > > > > > convoluted, and it's a lot simpler to use the NoSQL > in-memory > > > > > > persistence > > > > > > > > > instead. > > > > > > > > > > > > > > > > > > Cheers, > > > > > > > > > Dmitri. > > > > > > > > > > > > > > > > > > On Mon, Jun 29, 2026 at 1:57 PM Alexandre Dutra < > > > > [email protected]> > > > > > > wrote: > > > > > > > > > > > > > > > > > > > Hi all, > > > > > > > > > > > > > > > > > > > > Some updates on this: > > > > > > > > > > > > > > > > > > > > I recently started a separate discussion regarding > dynamic > > > > > > datasource > > > > > > > > > > activation at runtime [1]. This was intended as a > > prerequisite > > > > for > > > > > > > > > > adopting H2 as the default JDBC driver, as suggested on > > this > > > > > > thread. > > > > > > > > > > > > > > > > > > > > However, that proposal may end up being rejected. > > > > > > > > > > > > > > > > > > > > Given this situation, we should reconsider our options. > If > > the > > > > > > > > > > PostgreSQL + H2 approach is no longer a viable > replacement > > to > > > > the > > > > > > > > > > TreeMapMetaStore, I propose an alternative: let's use the > > NoSQL > > > > > > > > > > metastore with an InMemory backend. > > > > > > > > > > > > > > > > > > > > My reasoning is as follows: > > > > > > > > > > > > > > > > > > > > 1. It remains a production-ready metastore, so strictly > > > > superior to > > > > > > > > > > TreeMapMetaStore. > > > > > > > > > > > > > > > > > > > > 2. The metastore state update logic is the same > regardless > > of > > > > the > > > > > > > > > > backend, so we're still close to a real production setup > > (same > > > > as > > > > > > with > > > > > > > > > > an in-memory JDBC driver). > > > > > > > > > > > > > > > > > > > > 3. It doesn't require any external dependencies (no > bundled > > > > > > driver). > > > > > > > > > > > > > > > > > > > > I'd also note that while the NoSQL metastore is already > > > > included > > > > > > > > > > today, it is not actionable because no backend is > > available. > > > > This > > > > > > goes > > > > > > > > > > against the onboarding UX that we're trying to achieve, > as > > > > users > > > > > > > > > > interested in Polaris with the NoSQL metastore cannot > test > > this > > > > > > setup > > > > > > > > > > with the official image. > > > > > > > > > > > > > > > > > > > > Therefore, I think NoSQL + InMemory would serve as a more > > > > > > appropriate > > > > > > > > > > default setup for the official Polaris image. > > > > > > > > > > > > > > > > > > > > From what I see, it would boil down to adding one line to > > > > > > > > > > polaris-server or polaris-service: > > > > > > > > > > > > > > > > > > > > > > runtimeOnly(project(":polaris-persistence-nosql-db-inmemory")) > > > > > > > > > > > > > > > > > > > > What are your thoughts on this? > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > Alex > > > > > > > > > > > > > > > > > > > > [1]: > > > > > > https://lists.apache.org/thread/jy6wb186h94n9q86kv01shbn68ppr6gv > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Fri, Jun 19, 2026 at 12:07 PM Alexandre Dutra < > > > > > > [email protected]> > > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
