On Thu, Apr 16, 2020 at 8:52 AM Antoine Pitrou <[email protected]> wrote: > > > Hello, > > Let's an IPC Schema message contains the following Field (in pseudo-JSON > representation): > > { > "name" : "...", > "nullable" : true, > "type" : Utf8, > "dictionary": { > "id": 0, > "indexType": Int32, > "isOrdered": true > }, > "children" : [], > "metadata" : [ > {"key": "ARROW:extension:name", "value": "MyExtType"}, > {"key": "ARROW:extension:metadata", "value": "..."} > ] > } > > Which of the following two logical types does it represent? > > - MyExtType<storage = int32-dictionary<string>>
This one. > - int32-dictionary<MyExtType<storage = string> I do not believe this is representable in the IPC metadata protocol as it currently stands. So in C++ it would not be possible to roundtrip dictionary<ext_type>, this would have to be written as ext_type<dictionary>. > Regards > > Antoine.
