Unless I am missing something, I think the selection use-case could be equally well served by a dictionary-encoded BinarArray/ListArray, and would have the benefit of not requiring any modifications to the existing format or kernels.
The major additional flexibility of the proposed encoding would be permitting disjoint or overlapping ranges, are these common enough in practice to represent a meaningful bottleneck? On 26 April 2023 01:40:14 BST, David Li <lidav...@apache.org> wrote: >Is there a need for a 64-bit offsets version the same way we have List and >LargeList? > >And just to be clear, the difference with List is that the lists don't have to >be stored in their logical order (or in other words, offsets do not have to be >nondecreasing and so we also need sizes)? > >On Wed, Apr 26, 2023, at 09:37, Weston Pace wrote: >> For context, there was some discussion on this back in [1]. At that time >> this was called "sequence view" but I do not like that name. However, >> array-view array is a little confusing. Given this is similar to list can >> we go with list-view array? >> >>> Thanks for the introduction. I'd be interested to hear about the >>> applications Velox has found for these vectors, and in what situations >> they >>> are useful. This could be contrasted with the current ListArray >>> implementations. >> >> I believe one significant benefit is that take (and by proxy, filter) and >> sort are O(# of items) with the proposed format and O(# of bytes) with the >> current format. Jorge did some profiling to this effect in [1]. >> >> [1] https://lists.apache.org/thread/49qzofswg1r5z7zh39pjvd1m2ggz2kdq >> >> On Tue, Apr 25, 2023 at 3:13 PM Will Jones <will.jones...@gmail.com> wrote: >> >>> Hi Felipe, >>> >>> Thanks for the introduction. I'd be interested to hear about the >>> applications Velox has found for these vectors, and in what situations they >>> are useful. This could be contrasted with the current ListArray >>> implementations. >>> >>> IIUC it would be fairly cheap to transform a ListArray to an ArrayView, but >>> expensive to go the other way. >>> >>> Best, >>> >>> Will Jones >>> >>> On Tue, Apr 25, 2023 at 3:00 PM Felipe Oliveira Carvalho < >>> felipe...@gmail.com> wrote: >>> >>> > Hi folks, >>> > >>> > I would like to start a public discussion on the inclusion of a new array >>> > format to Arrow — array-view array. The name is also up for debate. >>> > >>> > This format is inspired by Velox's ArrayVector format [1]. Logically, >>> this >>> > array represents an array of arrays. Each element is an array-view >>> (offset >>> > and size pair) that points to a range within a nested "values" array >>> > (called "elements" in Velox docs). The nested array can be of any type, >>> > which makes this format very flexible and powerful. >>> > >>> > [image: ../_images/array-vector.png] >>> > <https://facebookincubator.github.io/velox/_images/array-vector.png> >>> > >>> > I'm currently working on a C++ implementation and plan to work on a Go >>> > implementation to fulfill the two-implementations requirement for format >>> > changes. >>> > >>> > The draft design: >>> > >>> > - 3 buffers: [validity_bitmap, int32 offsets buffer, int32 sizes buffer] >>> > - 1 child array: "values" as an array of the type parameter >>> > >>> > validity_bitmap is used to differentiate between empty array views >>> > (sizes[i] == 0) and NULL array views (validity_bitmap[i] == 0). >>> > >>> > When the validity_bitmap[i] is 0, both sizes and offsets are undefined >>> (as >>> > usual), and when sizes[i] == 0, offsets[i] is undefined. 0 is recommended >>> > if setting a value is not an issue to the system producing the arrays. >>> > >>> > offsets buffer is not required to be ordered and views don't have to be >>> > disjoint. >>> > >>> > [1] >>> > >>> https://facebookincubator.github.io/velox/develop/vectors.html#arrayvector >>> > >>> > Thanks, >>> > Felipe O. Carvalho >>> > >>>
