Hi all, Based on the points raised above and a few adventures implementing some of this in related projects, I put together a brief design document proposing a scope and structure to perhaps solidify a few of these discussions: https://docs.google.com/document/d/11n7ICVZO8exZ-z3GRlI26VLzKPXlYlEz5xjLl1y0ujU/edit?usp=sharing .
Any and all should feel free to add, rewrite, or propose a new structure...I wrote many of the pieces for argument's sake or because that's how I'd implemented them before. Next week I will phrase it as a skeleton header (like the one in the excellent ADBC design discussions) depending on feedback to keep the discussion going! Cheers, -dewey On Fri, Jun 3, 2022 at 9:57 AM Hannes Mühleisen <han...@duckdblabs.com> wrote: > Hello List, > > we at DuckDB are happy users of the Arrow C Data Interface and use it to > feed SQL queries and also use it to provide query results in Arrow format > again. It is particularly appealing to us that the interface is merely a > (C) header file that we just ship with our source code [1]. Internally, our > implementation then constructs DuckDB internal vectors from the Arrow > format [2] or vice-versa [3]. > > As you can see from [2, 3] there is some complexity in getting the > conversion right, especially for more complex data types like nested types > (list, strings). A lightweight, dependency-free library to help > constructing those would certainly be appreciated. What would also help a > lot is validation code, Arrow structures are very delicate and one wrong > pointer can lead to disaster (which is then blamed on us), so a way to > verify the structures in said lightweight library would be very helpful. > > Best from Amsterdam, and Quack > > Hannes > > [1] > > https://github.com/duckdb/duckdb/blob/master/src/include/duckdb/common/arrow.hpp > [2] > https://github.com/duckdb/duckdb/blob/master/src/function/table/arrow.cpp > [3] > > https://github.com/duckdb/duckdb/blob/master/src/common/types/data_chunk.cpp > > > On Fri, Jun 03, 2022 at 15:34:42, Jonathan Keane <jke...@gmail.com> wrote: > > > cc Hannes Mühleisen from DuckDB Labs > > > > -Jon > > > > > > On Tue, May 31, 2022 at 5:03 PM Wes McKinney <wesmck...@gmail.com> > wrote: > > > > I'm also supportive of having a small vendorable C/C++ "Arrow > > middleware" that provides: > > > > * Schemas and types > > * Columnar data structures and minimal APIs to build them and iterate > over > > them > > * C data interface > > * Minimal validation (at the level of Validate but not ValidateFull) > > > > I don't think it's going to be practical to try to refactor parts of > > the existing Arrow C++ core to be vendorable since there are many > > features / requirements (e.g. an extensible buffer and device API) > > that these C++ classes include that aren't needed in this > > limited-feature middleware library. > > > > This also relates to the "Improving Arrow's database support" project > > that David Li raised some time ago [1]. If we want to encourage > > database driver libraries to add new APIs that emit the Arrow C > > interface, we need to make it easier to generate the C interface > > without requiring a new library dependency. > > > > [1]: https://lists.apache.org/thread/gnz1kz2rj3rb8rh8qz7l0mv8lvzq254w > > > > On Mon, May 30, 2022 at 11:31 AM Jonathan Keane <jke...@gmail.com> > wrote: > > > > > > Thanks for working on this. I've heard people asking about something > > > like this from a number of different fronts on top of the obvious use > > > case in geoarrow | other geospatial libraries. I think a minimal piece > > > of Arrow that other packages could depend on without needing to bring > > > in all of arrow would be super valuable in building the bridges we > > > want across other systems. > > > > > > Do you have any (design) documentation that describes the scope of > > > what you're thinking? I know there have been others floating around > > > [1] [2] that were in a similar spirit. > > > > > > A few more questions I hope will spark more conversation: How do the > > > header files you linked in [3] overlap with these other efforts? Are > > > those headers something we could|should "just" PR into apache/arrow > > > and write up how to use them? If not what is the work to make them so > > > that they could be (the answer of course could be design something > > > else entirely and PR that!)? > > > > > > [1] https://github.com/paleolimbot/narrow > > > [2] https://paleolimbot.github.io/narrow/articles/why-narrow.html > > > [3] > https://github.com/paleolimbot/geoarrow-cpp/tree/main/src/geoarrow/ > > internal/arrow-hpp > > > > > > -Jon > > > > > > -Jon > > > > > > > > > On Wed, May 25, 2022 at 9:29 AM Dewey Dunnington < > de...@voltrondata.com> > > wrote: > > > > > > > > I'm writing to gauge interest in a set of helpers in C and/or C++ for > > > > reading/exporting Arrow C Data interface structures. My use-case is > > > > building Arrow geospatial support in R [1], and while the set of > > helpers > > > > I've been using [2] has served the purpose of me writing about the > > > > opportunities for Arrow + geospatial [3], I would like to rewrite the > > > > prototype based on something developed by/with the Arrow community. > > > > > > > > Does a set of C/C++ helpers for Arrow C Data interface structures > > already > > > > exist? *Should* it exist? > > > > > > > > If it doesn't, what should the name/scope of that library be? The > names > > > > 'nanoarrow', 'narrow', 'sparrow', and 'arrow-hpp' have all surfaced > in > > my > > > > limited discussion of this so far. For the purpose of starting the > > > > discussion, I'll posit that the library should include helpers to > > > > allocate/destroy C Data interface structures, a schema metadata > > > > encoder/decoder, validation of a schema/array pair, and something > like > > the > > > > ArrayBuilder C++ class. > > > > > > > > [1] https://lists.apache.org/thread/yb7p9wpg3k128njskhwj9j788opb67g7 > > > > [2] > > > > https://github.com/paleolimbot/geoarrow-cpp/tree/main/src/geoarrow/ > > internal/arrow-hpp > > > > [3] > > > > https://docs.google.com/document/d/ > > 1A6e3XCerjhXVFHBDaoAlBBNFb2HG4RB9SVRpuBru7E4/edit?usp=sharing > > > > >
