Hi Keith, Thank you for the follow-up.
You are correct that FieldRoaringBitmap64Agg already exists in fluss-server. I have updated the proposal accordingly. To clarify, the 32-bit scope is intended to keep the initial type system and SQL function surface focused and deliverable, rather than being a limitation of the aggregator itself. Since the server-side aggregator is already in place, RBM64 will be a natural, low-risk follow-on once the type system and pushdown infrastructure are established. I have also removed the misleading motivation paragraph as you suggested. The updated document is available at the same link. Additionally, I would welcome Yang's input on the alignment with FIP-21. Best regards, Prajwal Banakar On Wed, 11 Mar 2026 at 17:37, Keith Lee <[email protected]> wrote: > Hi Prajwal, > > Thank you for addressing / answering the questions. > > > This proposal adds the missing bridge: a proper BITMAP DDL type, SQL > functions (BITMAP_BUILD, BITMAP_OR_AGG, BITMAP_CARDINALITY), and pushdown > via applyAggregates(). The storage-side aggregation logic already exists; > this proposal makes it accessible end-to-end > > 1. That makes sense. I think the motivation section should lead with that > and remove the following as it can be misleading given that rbm is > supported by aggregation merge engine: “users requiring high-cardinality > unique counting (e.g., UV analytics) must execute Client-Side Aggregation. > The TabletServer is forced to send massive amounts of raw LogRecordBatch > rows over the network to a Flink cluster for evaluation. This results in > unnecessary network transfer and prevents efficient utilization of the > existing aggregation merge engine.” > > 2. That makes sense. Thank you for the context. > > 3. > > > RBM64 requires a fundamentally different internal structure; a map of > RBM32 chunks which increases implementation and serialization complexity > significantly. > > My understanding is that the proposal wires existing > FieldRoaringBitmap32Agg to support rbm32. FieldRoaringBitmap64Agg should > already exist and handle the complexity that you mentioned? > > Additionally, it might be good for Yang to review / provide input on this > given his work on FIP-21. > > Best regards > > Keith Lee > > > On Wed, 11 Mar 2026 at 05:49, Prajwal Banakar <[email protected]> > wrote: > > > Hi Keith, thank you for the detailed feedback. > > > > 1. On motivation vs existing aggregation merge engine: The aggregation > > merge engine in 0.9 supports rbm32/rbm64 at the storage level, but BITMAP > > is not yet a first-class type in the DDL or type system. Users today must > > declare the column as BYTES (as shown in the 0.9 release example: > uv_bitmap > > BYTES), and there are no SQL functions to build, merge, or query bitmaps > > from Flink SQL. This proposal adds the missing bridge: a proper BITMAP > DDL > > type, SQL functions (BITMAP_BUILD, BITMAP_OR_AGG, BITMAP_CARDINALITY), > and > > pushdown via applyAggregates(). The storage-side aggregation logic > already > > exists; this proposal makes it accessible end-to-end. > > > > 2. On NULL semantics: BITMAP_OR(bitmap, NULL) returns NULL following > > standard SQL scalar function semantics where NULL inputs propagate to > NULL > > outputs. BITMAP_OR_AGG follows aggregate function convention consistent > > with how SUM and AVG behave, where NULLs in individual rows are skipped > and > > only a fully NULL input set returns NULL. This distinction follows > FLIP-556 > > and StarRocks semantics. > > > > 3. On 32-bit scope: The proposal is scoped to 32-bit initially because > > RoaringBitmap32 covers integer values up to 2^32 (~4 billion), which is > > sufficient for most user ID and session ID use cases. RBM64 requires a > > fundamentally different internal structure; a map of RBM32 chunks which > > increases implementation and serialization complexity significantly. > > Starting with 32-bit keeps the initial scope focused and deliverable. > RBM64 > > support is listed as a Could-Have in the MoSCoW deliverables and can > follow > > in a subsequent iteration. > > > > Best regards, > > > > Prajwal Banakar > > > > > > On Wed, 11 Mar 2026 at 01:34, Keith Lee <[email protected]> > > wrote: > > > > > Hello Prajwal, > > > > > > Thank you for the detailed proposal. I enjoyed reading it and have a > few > > > questions/comments. > > > > > > 1. On motivation, can you provide context on how this differs with > > > aggregation merge engine’s roaring bitmap implementation [1]? > > Specifically, > > > motivation part states that “users requiring high cardinality unique > > > counting … must execute client-side aggregation”. Aggregation merge > > engine > > > performs aggregation on server-side. The motivation section should > > clarify > > > how the proposed changes improve or complement aggregation merge > engine, > > > which seems to have been considered as Section 2 references FIP-21 > > > Aggregation Merge Engine. Adding this context will help readers > > understand > > > the motivation of the proposal better. > > > > > > 2. Can you clarify the NULL semantics section specifically on the > > decision > > > on why BITMAP_OR(bitmap, NULL) returns NULL but BITMAP_OR_AGG only > > returns > > > null when all rows are NULL? > > > > > > 3. Why is the scope limited to 32 bit bitmaps? Adding the rationale > > behind > > > these e.g. how (if any) support of 64bit bitmaps would increase > > > implementation complexity. Articulating these may help other > contributors > > > understand the complexity and perhaps come up with suggestions on how > to > > > address them. > > > > > > Best regards > > > > > > Keith Lee > > > > > > [1] > > > > > > > > > https://fluss.apache.org/blog/releases/0.9/#2-storage-level-processing--semantics > > > > > > > > > On Mon, 9 Mar 2026 at 05:31, Prajwal Banakar < > [email protected] > > > > > > wrote: > > > > > > > Hi Devs, > > > > > > > > I have pushed a working prototype to my public fork demonstrating the > > > > BitmapType integrated with FieldRoaringBitmap32Agg. This includes > four > > > > passing unit tests. > > > > > > > > The link to the prototype is available in the Google Doc, and you can > > > also > > > > find it here: > > > > > https://github.com/Prajwal-banakar/fluss/tree/RoaringBitmap-prototype > > > > > > > > The Google Doc link remains the same. I look forward to your > feedback. > > > > > > > > Best regards, > > > > > > > > Prajwal Banakar > > > > > > > > > > > > On Sun, 1 Mar, 2026, 11:49 am Prajwal Banakar, < > > > [email protected] > > > > > > > > > wrote: > > > > > > > > > Hi everyone, > > > > > > > > > > I would like to start a discussion on the proposal for Native > Bitmap > > > > > Integration & Stateless Pushdown Aggregation. > > > > > > > > > > This proposal enables end-to-end native support for the BITMAP type > > in > > > > > Fluss and integrates it with the existing aggregation merge engine > to > > > > > support server-side bitmap union pushdown. The goal is to reduce > > > network > > > > > transfer and offload DISTINCT-style aggregation from Flink to the > > > > > TabletServer. > > > > > > > > > > Key highlights of the proposal include: > > > > > > > > > > - Type System: Promoting BITMAP to a first-class logical type. > > > > > - UDF Suite: Introducing BITMAP_BUILD, BITMAP_OR_AGG, and > > > > > BITMAP_CARDINALITY (aligned with FLIP-556 and StarRocks semantics). > > > > > - Optimizer: Planner-based pushdown via applyAggregates in the > Flink > > > > > connector. > > > > > - Safety: No changes to LogRecordBatch or WAL, making this strictly > > > > > additive and migration-free. > > > > > > > > > > You can find the full proposal document here: > > > > > > > > > > > > > > > > > > > > https://docs.google.com/document/d/1sDhfkmo-w-UTvo2n3rsY1lytSSryswfkI83cSdka8s0/edit?usp=sharing > > > > > > > > > > I would appreciate feedback on the public interfaces, pushdown > > > > > constraints, and overall scope. > > > > > > > > > > Best regards, > > > > > Prajwal Banakar > > > > > > > > > > > > > > >
