> Can you explain what ADT means ? Sorry about that. ADT stands for Abstract Data Type. What do I mean by an ADT style vector?
Let's take an example from the project I am on. We have an `op` union vector with three child vectors `put`, `delete`, `erase`. `delete` and `erase` have the same type but represent different things. On Tue, 2 Apr 2024 at 13:16, Steve Kim <chairm...@gmail.com> wrote: > Thank you for asking this question. I have the same question. > > I noted a similar problem in the c++/python implementation: > https://github.com/apache/arrow/issues/19157#issuecomment-1528037394 > > On Tue, Apr 2, 2024, 04:30 Finn Völkel <f...@juxt.pro> wrote: > > > Hi, > > > > my question primarily concerns the union layout described at > > https://arrow.apache.org/docs/format/Columnar.html#union-layout > > > > There are two ways to use unions: > > > > - polymorphic vectors (world 1) > > - ADT style vectors (world 2) > > > > In world 1 you have a vector that stores different types. In the ADT > world > > you could have multiple child vectors with the same type but different > type > > ids in the union type vector. The difference is apparent if you want to > use > > two BigIntVectors as children which doesn't exist in world 1. World 1 is > a > > subset of world 2. > > > > The spec (to my understanding) doesn’t explicitly forbid world 2, but the > > implementation we have been using (Java) has been making the assumption > of > > being in world 1 (a union only having ONE child of each type). We > sometimes > > use union in the ADT style which has led to problems down the road. > > > > Could someone clarify what the specification allows and what it doesn’t > > allow? Could we tighten the specification after that clarification? > > > > Best, Finn > > >
