On Thu, Apr 14, 2011 at 7:23 PM, Justin Deoliveira <[email protected]>wrote:
> Sorry, I meant to ask about *paging* on all stores.
>>
>
> Right, but to do paging consistently implicitly requires sorting since you
> can't rely 100% of the time on a data source returning features in
> a consistent ordering. Or am I missing something?
>
Justin, you're right, the store is otherwise free to return the data in
whatever
order it pleases. This the case in which the data to be returned is read
along
a spatial index, while you access someone makes a transaction, changes
features, the index gets modified and rebalanced and as a result you get
whole blocks of features returned in a different order (if you're lucky it's
only
just one that moves, but that cannot be guaranteed).
Sorting ensures that only the features modified move in the list instead.
However as you said we might have to give up sorting on the less complete
data sources in order to give some sort of paging support. The sources
I'm thinking about (shapefiles, files in general) are not suites for WFS-T
anyways,
so we may try to be more lenient.
I guess the store should advertise "non stable paging" as opposed to "stable
paging" that requires a sort to keep it straigth
Cheers
Andrea
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