IIUC, the point is to have different logical views over the same data. So you could have e.g. a "sorted" view. You could also have a view spanning a tiny fraction of the original data (you can probably also encode that with a null bitmap, but if most values are nulls that is less efficient).
Regards Antoine. Le 01/05/2018 à 15:24, Brian Hulette a écrit : > Yeah I see that difference. I guess my question was really - is there a > reason not to re-arrange the actual list data so that an offset array > will work? > > Perhaps they actually want to be able to specify lists with overlap? Or > maybe there is meaning to the original order of the list data? I suppose > that latter option seems more likely. > > Brian > > > On 04/30/2018 05:42 PM, Antoine Pitrou wrote: >> Le 30/04/2018 à 23:39, Brian Hulette a écrit : >>> Yes my first reaction to both of these requests is >>> - would dictionary-encoding work? >>> - would a List<T> work? >>> >>> I think for the former the analogy is more clear, for the latter, >>> technically a List encodes start and stop indices with an offset array >>> rather than separate arrays for start and stop indices. Is there a >>> reason an offset array wouldn't work for the OAMap use-case though? >> With an offsets array, spans (lists) are contiguous: span N + 1 starts >> off where span N stops. With separate start/stops array, they needn't >> be: the logical array can "walk" the physical array in any order. >> >> Regards >> >> Antoine. >
