Hi Hongshun, Thanks, this sounds like a very useful landing case. Since StarRocks support relies on the same union-read / Paimon lake path covered by Theme 2, it fits the direction well. From the fluss-rust side, I think the important part is to define the common union-read semantics clearly, and then make sure the Rust client and C++ bindings expose the right primitives for integrations like StarRocks to build on.
So this looks like a good validation of the Theme 2 direction, and also a useful reminder that the lake/log union read should not be DataFusion-specific. -- Anton пт, 3 июл. 2026 г. в 09:10, Hongshun Wang <[email protected]>: > > Hi Anton, > We will also support union read in StarRocks in Fluss C++ ( > https://github.com/StarRocks/starrocks/issues/75785), and Yangyang( > https://github.com/naivedogger) and I will do it. This way, our Rust client > ecosystem can become more than just a demo. > > Best, > Hongshun > > On Fri, Jul 3, 2026 at 3:42 PM Anton Borisov <[email protected]> wrote: > > > Hi all, > > > > Thanks Forward, Hongshun and Junbo. > > > > On the release framing: I agree we should avoid making "0.3.0" the > > public target name once fluss-rust is consolidated into the main Fluss > > repo. It was a useful shorthand while fluss-rust had its own > > versioning, but after FIP-40 it is probably clearer to talk about the > > next post-consolidation Fluss release scope. > > My reading is that consensus is forming around the following shape, so > > let's define the roadmap like this for the time being: > > > > Theme 1 DataFusion integration adapter > > This looks like the main must-have item. There seems to be agreement > > that it should be a standalone adapter over the Rust core, not a > > bundled engine, and that Arrow/DataFusion versions should be pinned > > consistently across the workspace. > > > > Theme 2 Lake + log union read > > This also looks like a must-have scope. Paimon-first seems to be the > > pragmatic path, with the lake-side dependencies isolated in a separate > > crate. We should be careful with the boundary semantics for PK tables, > > especially how newer log records are applied over the lake snapshot. > > > > Theme 3 Predicate pushdown > > There also seems to be agreement that predicate pushdown is > > high-value, especially for both the DataFusion adapter and gateway > > read paths. I would still keep it as stretch unless based on the > > current capacity and amount of contributors. In the interim, we can > > push predicates into the lake side where supported and apply the > > remaining filters over the real-time log tail. > > > > Theme 4 Gateway > > For Gateway, I think the discussion is converging toward treating it > > as a separate FIP from the core fluss-rust roadmap, especially if we > > split the plain REST API and SQL surface. > > > > The auth/authz questions Hongshun raised are important and probably > > belong in that Gateway design rather than being hidden inside the rust > > roadmap. My initial take is that gateway-side authentication can be > > independent, but authorization should stay aligned with Fluss > > server-side ACL semantics. Whether the gateway uses a single service > > identity or delegated user identities is a real design choice and > > affects connection management, so it deserves explicit discussion in > > the Gateway FIP. > > > > On the production-readiness gap Hongshun mentioned: I agree this is > > important, but I would separate it from the analytical surface itself. > > The goal is to close these gaps, while first bringing the core > > capabilities into place. I would treat this as a separate > > production-readiness track/umbrella issue as part of the > > post-consolidation work. Once fluss-rust is consolidated into the main > > repo, we should also test it regularly against the current Fluss > > build, so compatibility and stability issues are caught earlier. > > > > For today’s community meeting, I added the fluss-rust roadmap topic. I > > can summarize the dev@ discussion so far and keep it clearly framed as > > discussion status, not a final decision. Junbo, it would be good if > > you could also briefly cover the prototype /lake kernel /gateway parts > > you explored in code. It will be useful to understand the scope and > > the work we can integrate back. > > > > -- Anton > > > > пт, 3 июл. 2026 г. в 07:42, Junbo Wang <[email protected]>: > > > > > > Hi Hongshun, > > > > > > Good point — fluss-rust is currently at 0.1.0 with master tracking > > 0.2.0, so "0.3.0" was just our shorthand here. Once FIP-40 lands and > > fluss-rust moves into the fluss repo, it would naturally follow fluss > > versioning — likely the release after 1.0. I'll update the framing to > > reflect that. > > > > > > > > > Best regards, > > > Junbo Wang > > > > > > > 2026年7月3日 14:16，Hongshun Wang <[email protected]> 写道： > > > > > > > > Hi Junbo, > > > > What's 0.3.0? Since fluss-rust will be merged into fluss repo, maybe > > fluss > > > > release-1.0? > > > > > > > > Best, > > > > Hongshun > > > > > > > > On Fri, Jul 3, 2026 at 11:27 AM Junbo Wang <[email protected]> > > wrote: > > > > > > > >> Thanks Forward and Hongshun for the thoughtful input. > > > >> > > > >> On ForwardXu's question about the target release — I've been thinking > > a > > > >> bit about the 0.3.0 scope, and would like to share my personal take, > > mostly > > > >> as a starting point for discussion. > > > >> > > > >> A possible 0.3.0 scope > > > >> > > > >> FIP-40: consolidate fluss-rust into apache/fluss. thanks to Anton for > > > >> already opening the PR-3401 < > > https://github.com/apache/fluss/pull/3401> > > > >> DataFusion integration adapter (Theme 1), as a fluss-rust submodule. > > > >> Lake + log union read, Paimon-first (Theme 2), as a separate > > submodule so > > > >> lake-side dependencies stay isolated from the core. S > > > >> erver-side filter pushdown (Theme 3) — would be great to have if > > capacity > > > >> allows, but I'd suggest keeping it optional rather than a hard > > requirement > > > >> for 0.3.0. > > > >> > > > >> Gateway — perhaps outside 0.3.0 > > > >> > > > >> Once fluss-rust is consolidated into apache/fluss, it might make > > sense for > > > >> the gateway to live as its own module depending on fluss-rust, rather > > than > > > >> being tied to the 0.3.0 release train. That would also give the > > auth/authz > > > >> questions Hongshun raised some room to be designed in a dedicated FIP. > > > >> > > > >> Just my personal thinking — happy to adjust based on what others feel > > is > > > >> right. > > > >> > > > >> > > > >> Best regards, > > > >> Junbo Wang > > > >> > > > >>> 2026年7月2日 11:47，Forward Xu <[email protected]> 写道： > > > >>> > > > >>> Hi Anton, > > > >>> > > > >>> Thanks for putting this together, and thanks to everyone who landed > > the > > > >>> previous roadmap. Framing the next phase around "fluss-rust as a > > > >>> first-class analytical query surface" makes a lot of sense to me — it > > > >>> builds naturally on the analytical primitives we just shipped. A few > > > >>> thoughts, roughly following your structure. > > > >>> > > > >>> *Theme 1 — DataFusion integration adapter [MUST-HAVE]* +1. I strongly > > > >> agree > > > >>> it should be an *adapter over the Rust core*, not a bundled engine. > > > >> Keeping > > > >>> fluss-datafusion as a standalone crate exposing TableProvider + > > > >>> CatalogProvider/SchemaProvider keeps the dependency direction clean > > and > > > >>> lets any DataFusion-based consumer (or the gateway) opt in. Mapping > > > >>> projection/filter/limit pushdown onto the existing access paths (PK > > > >>> equality → lookup, bucket-key prefix → prefix lookup, LIMIT → bounded > > > >> scan, > > > >>> else log scan) is the right approach. One thing worth nailing down > > early > > > >> is > > > >>> the exactness contract we report back to DataFusion ( > > > >>> TableProviderFilterPushDown::Exact vs Inexact), since getting that > > wrong > > > >>> silently drops or double-applies filters. > > > >>> > > > >>> *Theme 2 — Lake + log union read (Paimon-first) [MUST-HAVE]* +1, and > > > >>> Paimon-first is the right call — reusing paimon-rust by wrapping an > > > >>> existing reader is low-risk, and the lake-snapshot-records-log-offset > > > >>> design gives us a clean stitch point. Starting bounded-batch and > > > >> deferring > > > >>> streaming also de-risks correctness of the log-offset boundary > > before we > > > >>> add continuous reads. The main correctness edge I'd like to see > > covered > > > >> is > > > >>> the boundary semantics for PK tables when applying newer log records > > over > > > >>> the lake snapshot (dedup/ordering at the tiered offset). > > > >>> > > > >>> *Theme 3 — Foundations / server-side filter pushdown [STRETCH]* Agree > > > >> this > > > >>> is a stretch, but it's the item with the highest leverage since it > > prunes > > > >>> both lake and log scans and unblocks the gateway's filter pushdown. > > > >>> Cross-checking against the Java PredicateConverter semantics is > > important > > > >>> so both clients behave identically. If capacity allows, I'd lean > > toward > > > >>> pulling at least the simple value-predicate cases forward, since > > Themes 1 > > > >>> and 4 both benefit. > > > >>> > > > >>> *Theme 4 — Gateway [STRETCH]* The "REST is the no-regret floor, SQL > > is > > > >> the > > > >>> ceiling deferred until Themes 1–2" framing is a good way to think > > about > > > >> it. > > > >>> Keeping it a thin, stateless HTTP frontend over the existing client > > > >>> primitives (one endpoint per primitive) sounds right and keeps scope > > > >>> contained. > > > >>> > > > >>> *Open questions* > > > >>> > > > >>> - *Themes 1–2 must-have, rest stretch — reasonable?* Yes, ordering > > > >> looks > > > >>> right to me. Nothing obviously missing. > > > >>> - *Paimon first, Iceberg later?* Agree, provided the union-read > > path is > > > >>> written against a lake abstraction so Iceberg/Lance slot in the same > > > >> way > > > >>> rather than requiring a rewrite. > > > >>> - *Pin one arrow/DataFusion version across core, union-read/lake, > > and > > > >>> DF?* Strong +1 — we should pin a single Arrow/DataFusion version > > > >>> workspace-wide; version skew between these crates is a common and > > > >> painful > > > >>> source of breakage. > > > >>> - *Separate crates: lake kernel, DataFusion adapter, gateway?* +1 to > > > >>> separate crates. It matches the "adapter, not bundled engine" > > > >> principle and > > > >>> keeps the DataFusion dependency out of the core for consumers that > > > >> don't > > > >>> need it. > > > >>> > > > >>> One meta-question: do we have a rough sense of the target release > > > >> (0.3.0?) > > > >>> these must-haves land in, so we can size the Theme 3/4 stretch work > > > >>> accordingly? > > > >>> > > > >>> Thanks again — happy to help on the DataFusion adapter side. > > > >>> > > > >>> Best, > > > >>> > > > >>> ForwardXu > > > >>> > > > >>> Junbo Wang <[email protected]> 于2026年7月1日周三 22:41写道： > > > >>> > > > >>>>> I'd also like us to focus on closing the gap with the Java client > > on > > > >>>> predicate pushdown. > > > >>>> Agreed — predicate pushdown is a great optimization, and the read > > path > > > >>>> will benefit significantly from it. > > > >>>> > > > >>>> > > > >>>> > > > >>>> One thing that was missing in upstream paimon-rust was an > > > >>>> object-store-safe existence check in the filesystem catalog. It > > checked > > > >>>> whether database/table directories “exist”, which works on local > > > >>>> filesystems but can fail on S3/OSS because those directories are > > just > > > >>>> prefixes, not real objects. I forked it to fix that, so lake reads > > can > > > >>>> reliably open Paimon tables from object storage. > > > >>>> > > > >>>> Thanks again, Anton, for putting this roadmap together! I think we > > could > > > >>>> share it at the July 3rd community meeting. I've also been working > > on > > > >> some > > > >>>> designs around lake kernel read and the Fluss Gateway REST API — > > happy > > > >> to > > > >>>> discuss those as well if time allows. > > > >>>> > > > >>>> > > > >>>> Best regards, > > > >>>> Junbo Wang > > > >>>> > > > >>>>> 2026年6月25日 07:23，Anton Borisov <[email protected]> 写道： > > > >>>>> > > > >>>>> Hi Yuxia and Junbo, > > > >>>>> > > > >>>>> Yuxia, on PK changelog reads across the bindings: I have already > > > >>>>> prepared record-mode CDC for Rust, Python and C++. It's small, and > > > >>>>> the PK union read in Theme 2 needs it anyway. > > > >>>>> > > > >>>>> Junbo, I looked through your prototype branch. It is clear that a > > lot > > > >>>>> of Themes 1, 2 and 4 already exist there as working code and it > > does > > > >>>>> seem to answer two of the open questions: the three-way crate split > > > >>>>> (lake kernel / adapter / gateway), and pinning a single > > > >> Arrow/DataFusion > > > >>>>> version at the workspace level. +1 to both. > > > >>>>> > > > >>>>> Two separate FIPs with detailed design for REST/SQL gateway parts - > > > >>>> makes sense. > > > >>>>> > > > >>>>> One thing I noticed and want to discuss: > > > >>>>> The "lake read" currently depends on a fork of paimon-rust, can you > > > >> share > > > >>>>> what was missing in paimon-rust? > > > >>>>> > > > >>>>> I'd also like us to focus on closing the gap with the Java client > > on > > > >>>>> predicate pushdown. > > > >>>>> In the interim we can push predicates into the lake (Paimon already > > > >>>>> supports it) and apply them as a filter pass over the real-time log > > > >>>>> tail. > > > >>>>> > > > >>>>> Good to hear you want to drive this forward, given the prototype, > > that > > > >>>>> makes sense to me. I am happy to review the design and following > > PRs. > > > >>>>> > > > >>>>> Looking forward to the write-up with your findings. > > > >>>>> > > > >>>>> -- Anton > > > >>>>> > > > >>>>> вт, 23 июн. 2026 г. в 15:10, Junbo Wang <[email protected]>: > > > >>>>>> > > > >>>>>> Thanks Anton for kicking this off — funnily enough, I'd been > > arriving > > > >>>> at very similar conclusions while prototyping on my side, so let me > > > >> share a > > > >>>> bit of what came out of those experiments. > > > >>>>>> > > > >>>>>>> THEME 1: DATAFUSION INTEGRATION ADAPTER [MUST-HAVE] > > > >>>>>> > > > >>>>>> Agree. Having the DataFusion integration live in fluss-rust would > > make > > > >>>> it reusable across more downstream projects. One thing we might > > want to > > > >>>> keep in mind: it would probably be worth aligning the DataFusion and > > > >> Arrow > > > >>>> versions with pg-datafusion so the whole stack stays on a consistent > > > >> set of > > > >>>> versions. > > > >>>>>> > > > >>>>>>> THEME 2: LAKE + LOG UNION READ (PAIMON-FIRST) [MUST-HAVE] > > > >>>>>> > > > >>>>>> Agree. I'd lean toward putting this in a separate fluss-lake > > module > > > >>>> that exposes a client capable of doing the union read over the lake > > and > > > >> the > > > >>>> Fluss log. That way the lake-side dependencies stay isolated in > > their > > > >> own > > > >>>> module and don't bleed into the core fluss-rust code. One thing that > > > >> might > > > >>>> be worth flagging here: the lake side already supports predicate > > > >> pushdown, > > > >>>> while Fluss doesn't yet — so we'd probably think about how the union > > > >> read > > > >>>> handles that asymmetry in the interim. > > > >>>>>> > > > >>>>>> THEME 4: GATEWAY [STRETCH] — A thin HTTP frontend over the client > > > >>>>>> > > > >>>>>> I wonder if we could expand on this one a bit. My suggestion > > would be > > > >>>> to split the SQL REST surface and the plain REST API into two > > separate > > > >>>> FIPs. A read/write REST API on its own — somewhat in the spirit of > > > >>>> kafka-rest, covering reads, writes, and metadata management — would > > > >> already > > > >>>> be a quick win for broadening Fluss's data ingestion/access reach, > > and > > > >> it > > > >>>> doesn't depend on anything else. The SQL REST surface, on the other > > > >> hand, > > > >>>> has to wait on Themes 1–2, so it might make sense to split them and > > ship > > > >>>> the plain REST API first. > > > >>>>>> > > > >>>>>> > > > >>>>>> > > > >>>>>> Also, it might make sense to have the gateway as a separate crate > > > >>>> inside the Fluss project itself — especially since fluss-rust will > > be > > > >>>> moving into the Fluss repo anyway. > > > >>>>>> > > > >>>>>> On a personal note, this is something I'm really excited about and > > > >>>> would love to help push forward. I'll share a write-up of what came > > out > > > >> of > > > >>>> my demo experiments with the community over the next few weeks. > > > >>>>>> > > > >>>>>> > > > >>>>>> Best regards, > > > >>>>>> Junbo Wang > > > >>>>>> > > > >>>>>>> 2026年6月23日 20:55，Yuxia Luo <[email protected]> 写道： > > > >>>>>>> > > > >>>>>>> Thanks for putting this together. +1 on the overall framing. My > > > >>>> answers to the open questions, plus one addition: > > > >>>>>>> > > > >>>>>>> Open questions: > > > >>>>>>> - Themes 1-2 as must-have, rest stretch: agree, the ordering > > makes > > > >>>> sense to me. > > > >>>>>>> - Paimon first, Iceberg later: +1. Reusing paimon-rust is the > > > >>>> pragmatic path, and the union-read design generalizes to Iceberg the > > > >> same > > > >>>> way later. > > > >>>>>>> - Pin one arrow/DataFusion version across core, union-read/lake, > > and > > > >>>> DF: yes, we should pin a single version. Letting these drift will > > cause > > > >>>> painful Arrow type/ABI mismatches across the crate boundary, so a > > shared > > > >>>> pinned version (bumped deliberately, not per-crate) is worth the > > > >> discipline. > > > >>>>>>> - Separate crates (lake kernel, DataFusion adapter, gateway): +1 > > on > > > >>>> separate crates. It keeps the dependency surface clean - the > > adapter and > > > >>>> gateway are optional consumers, and the lake kernel shouldn't drag > > > >>>> DataFusion into anyone who only needs the core read path. > > > >>>>>>> > > > >>>>>>> One addition I'd like to propose for the scope: > > > >>>>>>> PK-table CHANGELOG read, and expose it across the bindings - > > > >>>> specifically C++ and Python - so non-Rust CDC consumers can > > subscribe. > > > >>>>>>> > > > >>>>>>> On 2026/06/22 14:49:52 Anton Borisov wrote: > > > >>>>>>>> Hi all, > > > >>>>>>>> > > > >>>>>>>> With the previous roadmap wrapping up - complex types > > > >>>>>>>> (Array/Row/Map/nesting), limit and prefix scan, schema-aware KV > > > >>>>>>>> decoding, the metrics framework, and write optimisations, > > thanks to > > > >>>>>>>> everyone who contributed and reviewed, I'd like to open > > discussion > > > >> on > > > >>>>>>>> the roadmap. > > > >>>>>>>> > > > >>>>>>>> I propose framing around a single goal: make fluss-rust a > > > >> first-class > > > >>>>>>>> analytical query surface - a Rust-native SQL/DataFrame path over > > > >> Fluss > > > >>>>>>>> (DataFusion, and through it Polars/DuckDB/gateways), reading the > > > >> lake > > > >>>>>>>> tier at scale, built on the analytical primitives we just > > landed. > > > >>>>>>>> > > > >>>>>>>> As before, I grouped the items into themes with an initial > > > >> must-have / > > > >>>>>>>> stretch positioning. Please push back where you disagree. > > > >>>>>>>> > > > >>>>>>>> THEME 1: DATAFUSION INTEGRATION ADAPTER [MUST-HAVE] > > > >>>>>>>> A standalone fluss-datafusion crate exposing TableProvider + > > Catalog > > > >>>>>>>> over the existing client, so SELECT ... FROM . works from any > > > >>>>>>>> DataFusion-based engine. It should be framed as an integration > > > >> adapter > > > >>>>>>>> over the Rust core, not a bundled engine. A gateway (FIP-32) or > > any > > > >>>>>>>> analytical consumer can use it or not. > > > >>>>>>>> > > > >>>>>>>> Scope: TableProvider + CatalogProvider/SchemaProvider backed by > > the > > > >>>>>>>> metadata path. > > > >>>>>>>> > > > >>>>>>>> Map DataFusion's projection/filter/limit pushdown onto the > > client's > > > >>>>>>>> existing access paths: a full primary-key equality becomes a > > > >> lookup, a > > > >>>>>>>> bucket-key prefix becomes a prefix lookup, LIMIT becomes a > > bounded > > > >>>>>>>> scan, otherwise a log scan. Filters an access path fully > > satisfies > > > >> are > > > >>>>>>>> reported exact, the rest are left for DataFusion to apply > > > >> (server-side > > > >>>>>>>> filter pushdown is Theme 3). > > > >>>>>>>> > > > >>>>>>>> THEME 2: LAKE + LOG UNION READ (PAIMON-FIRST) [MUST-HAVE] > > > >>>>>>>> A client-side read that presents a lake-enabled table as one > > table. > > > >>>>>>>> Its history is tiered to the lake (Paimon) and recent writes are > > > >> still > > > >>>>>>>> in the Fluss log, the lake snapshot records the log offset it > > > >> covers, > > > >>>>>>>> so we read the lake up to that offset and the Fluss log past it, > > > >> then > > > >>>>>>>> combine. > > > >>>>>>>> Scope: > > > >>>>>>>> - Per bucket: the lake snapshot plus the Fluss log past the > > tiered > > > >>>> offset. > > > >>>>>>>> - Log tables: concatenate the two. PK tables: apply the newer > > log > > > >>>>>>>> records to get current state. > > > >>>>>>>> - Paimon first, reusing paimon-rust, Iceberg/Lance later the > > same > > > >>>>>>>> way. The DataFusion adapter reads lake-enabled tables through > > this > > > >>>>>>>> path. > > > >>>>>>>> - Bounded batch first, streaming later > > > >>>>>>>> > > > >>>>>>>> Reusing paimon-rust means wrapping an existing reader, so it's > > > >> rather > > > >>>>>>>> feasible and straightforward. > > > >>>>>>>> > > > >>>>>>>> THEME 3: FOUNDATIONS [STRETCH] > > > >>>>>>>> Server-side value-predicate (filter) pushdown. The proto field > > > >> exists, > > > >>>>>>>> but the client currently sends none. This prunes lake/log scans > > and > > > >>>>>>>> unblocks the gateway's filter pushdown (the open question I > > raised > > > >> for > > > >>>>>>>> 0.2.0), cross-checked against the Java PredicateConverter > > semantics. > > > >>>>>>>> > > > >>>>>>>> THEME 4: GATEWAY [STRETCH] > > > >>>>>>>> A thin HTTP frontend over the client we already have > > independent of > > > >>>>>>>> Themes 1–3. It's how non-Rust/non-SQL clients (TS/JS, > > microservices, > > > >>>>>>>> curl) write to Fluss and do simple key access. > > > >>>>>>>> - Write: upsert/append, delete, create/drop tables, metadata. > > The > > > >>>>>>>> mature client write path essentially. > > > >>>>>>>> - Read: point lookup, prefix lookup, bounded log / CDC poll - > > one > > > >>>>>>>> endpoint per existing primitive, bounded and stateless. > > > >>>>>>>> The tradeoff: no joins, filters, or aggregations - that's the > > SQL > > > >>>>>>>> surface, and it needs the adapter and probably will be an > > ongoing > > > >>>>>>>> effort to optimise later. > > > >>>>>>>> - If Themes 1–2 ship, we unlock SQL frontends on top - > > PostgreSQL > > > >>>>>>>> via datafusion-postgres, as one example > > > >>>>>>>> In short: REST is the no-regret floor, SQL is the ceiling > > deferred > > > >>>>>>>> until Themes 1–2. > > > >>>>>>>> > > > >>>>>>>> PARALLEL TRACK: ELIXIR + BINDING EXPOSURE > > > >>>>>>>> Continue Elixir parity and expose newly-landed primitives > > (prefix > > > >>>>>>>> lookup, etc.) across Python / C++ / Elixir. > > > >>>>>>>> > > > >>>>>>>> GOVERNANCE TRACK > > > >>>>>>>> FIP-40: Consolidate apache/fluss-rust into apache/fluss - PR is > > > >> ready, > > > >>>>>>>> looks pretty good, waiting for a good moment to rebase/merge. > > > >>>>>>>> > > > >>>>>>>> OPEN QUESTIONS > > > >>>>>>>> - Themes 1–2 must-have, the rest stretch. Reasonable? Anything > > > >>>>>>>> missing or mis-ordered? > > > >>>>>>>> - Paimon first, Iceberg later? > > > >>>>>>>> - Pin one arrow/DataFusion version across core, > > union-read/lake, and > > > >>>> DF? > > > >>>>>>>> - Separate crates: lake kernel, DataFusion adapter, gateway? > > > >>>>>>>> > > > >>>>>>>> Looking forward to feedback. > > > >>>>>>>> > > > >>>>>>>> -- Anton > > > >>>>>>>> > > > >>>>>> > > > >>>> > > > >>>> > > > >> > > > >> > > > > >
