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Re: [Format] Pointer types / span types

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).



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.