As Boolean is already in the arrow type system I think it might be worth asking the question as to whether this should be an extension type or a first class type.
Given what I think of the last discussion on the trade-offs [1], I think there is room for debate here, since Boolean is not currently parameterized, adding it as an existing type would require a new top level type. Thanks, Micah [1] https://lists.apache.org/thread/3nls3222ggnxlrp0s46rxrcmgbyhgn8t On Wed, Jul 17, 2024 at 9:44 PM Alenka Frim <frim.ale...@gmail.com> wrote: > Thank you Joel for working on this! I have also came across > the need for a byte packed boolean support when implementing the > Python dataframe interchange protocol and also DPack which > is implemented in Arrow C++. The extension type is a great solution. > > I will comment on the PR if I have any questions. > > Alenka > > V V sre., 17. jul. 2024 ob 23:32 je oseba Ian Cook <ianmc...@apache.org> > napisala: > > > Thanks Joel and Matt. This looks good to me. > > > > I think it's worth saying here that Arrow-producing components should > still > > by default emit Booleans in the standard bit-packed Arrow layout. This > > proposed bool8 canonical extension type is intended to be used in > > applications where the producer knows that the consumer can correctly > > interpret the bool8 extension type and where using it is more efficient > > than converting the data to the standard bit-packed layout. > > > > Ian > > > > On Wed, Jul 17, 2024 at 5:19 PM Matt Topol <zotthewiz...@gmail.com> > wrote: > > > > > Just chiming in that the libcudf documentation[1] states that this > > proposal > > > should work just fine. Bool8 type is described as "0 == false, else > > true". > > > > > > --Matt > > > > > > [1]: > > > > > > > > > https://docs.rapids.ai/api/libcudf/stable/group__utility__types#gadf077607da617d1dadcc5417e2783539 > > > > > > On Wed, Jul 17, 2024, 3:18 PM Joel Lubinitsky <joell...@gmail.com> > > wrote: > > > > > > > Thank you for your comments. > > > > > > > > I spent some time trying to confirm definitively that this proposal > > would > > > > enable zero copy sharing both ways between pyarrow and numpy. I put > > > > together the following gist [1] with my experiment. > > > > > > > > To summarize the results: > > > > - I was able to share the underlying value buffer both ways and have > it > > > be > > > > interpreted correctly in each case. > > > > - Numpy will write 0 or 1 to the value buffer to indicate False or > > True. > > > > Importantly, numpy will also understand values outside this range to > > mean > > > > True without requiring a copy. This tracks closely with the proposed > > > > semantics. > > > > > > > > [1]: > https://gist.github.com/joellubi/2ddf626633b57839cfd5f32cd94a7f3b > > > > > > > > On Wed, Jul 17, 2024 at 10:16 AM Ian Cook <ianmc...@apache.org> > wrote: > > > > > > > > > >> Before the vote, I would like to see verification that this > truly > > > > > enables > > > > > >> zero-copy to/from NumPy bool arrays in Python. > > > > > > > > > > > I think this is an implementation issue more than a specification > > > > > issue...I am not personally worried about any provisions on the > > > > > specification that might make this impossible. > > > > > > > > > > To clarify, what I am looking for here is definite confirmation > that > > > > > the proposed representation (in which a signed int8 zero value > > > indicates > > > > > False and any non-zero signed int8 value indicates True) > corresponds > > to > > > > the > > > > > representation used by NumPy such that bidirectional zero-copy is > > made > > > > > possible. This seems to me like a specification issue. > > > > > > > > > > Ian > > > > > > > > > > On Wed, Jul 17, 2024 at 9:39 AM Dewey Dunnington > > > > > <de...@voltrondata.com.invalid> wrote: > > > > > > > > > > > Thank you for this! I have definitely run across the > > > one-byte-per-item > > > > > > bool in numpy, DuckDB, and cudf. I haven't heard any discussion > > about > > > > > > DuckDB here but I am fairly sure that they represent their > boolean > > > > > > type as an int8 as well [1]. > > > > > > > > > > > > > Before the vote, I would like to see verification that this > truly > > > > > enables > > > > > > > zero-copy to/from NumPy bool arrays in Python. > > > > > > > > > > > > I think this is an implementation issue more than a specification > > > > > > issue...I am not personally worried about any provisions on the > > > > > > specification that might make this impossible. > > > > > > > > > > > > -dewey > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > https://github.com/duckdb/duckdb/blob/85a82d86aa11a2695fc045deaf4f88fc63dd4fec/src/common/arrow/appender/bool_data.cpp#L28-L37 > > > > > > > > > > > > On Tue, Jul 16, 2024 at 11:25 AM Antoine Pitrou < > > anto...@python.org> > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > > Hi Joel, > > > > > > > > > > > > > > This looks good to me on the principle. Can you split the spec > > and > > > > the > > > > > > > implementation(s) into separate PRs? > > > > > > > > > > > > > > Regards > > > > > > > > > > > > > > Antoine. > > > > > > > > > > > > > > > > > > > > > Le 16/07/2024 à 13:18, Joel Lubinitsky a écrit : > > > > > > > > Hi Arrow devs, > > > > > > > > > > > > > > > > I'm working on adding an extension type for 8-bit booleans, > and > > > > > wanted > > > > > > to > > > > > > > > start a discussion about it here because it could be valuable > > to > > > > > > others if > > > > > > > > adopted as a canonical extension type. > > > > > > > > > > > > > > > > The native implementation of the Boolean type uses 1 bit to > > > encode > > > > > each > > > > > > > > value, enabling a very compact representation. This is > > favorable > > > > for > > > > > > many > > > > > > > > workloads, but lots of systems that want to produce/consume > > > Boolean > > > > > > arrays > > > > > > > > use an 8-bit representation internally and are forced to > > > > copy/convert > > > > > > at > > > > > > > > their periphery. For these scenarios where zero-copy > > > compatibility > > > > is > > > > > > > > important, the 8-bit representation of boolean values may be > > > > > preferred. > > > > > > > > This can benefit interactions with existing libraries that > > avoid > > > > > > packing > > > > > > > > column data like 1-bit booleans for parallelization purposes, > > > > > > including GPU > > > > > > > > libraries such as libcudf. The original issue [1] identifies > > > numpy > > > > > > > > conversion as a specific use-case as well. > > > > > > > > > > > > > > > > The details of the extension type can be found in the draft > PR > > > [2] > > > > > > which > > > > > > > > contains a Go implementation (WIP) and an update to the > > > > documentation > > > > > > for > > > > > > > > canonical extension types. I plan to add a C++ implementation > > as > > > > well > > > > > > but > > > > > > > > wanted to open this discussion first. > > > > > > > > > > > > > > > > A quick overview of the layout / semantics proposed in the > PR: > > > > > > > > Storage Type: Int8 > > > > > > > > Value Semantics: 0 == false, any non-zero value is true > > > > > > > > > > > > > > > > I'd appreciate any feedback here or on the PR. If this all > > seems > > > > > > reasonable > > > > > > > > then I'll move forward with the next implementation and open > up > > > > > another > > > > > > > > proposal for a formal vote. Thanks! > > > > > > > > > > > > > > > > [1]: https://github.com/apache/arrow/issues/17682 > > > > > > > > [2]: https://github.com/apache/arrow/pull/43234 > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
