[Archivesspace_Users_Group] Retrieving tree info via API (what are "waypoints"?)

[Trevor Thornton]

Thanks, Steve. That makes sense, and I tested with a resource with >1000
top level children and I see that only 200 of them are included, which
corresponds to the value for "waypoint_size" in the response:

{
>    "child_count":4780,
>    "waypoints":24,
>    "waypoint_size":200
> ...


So the next question is how do you make the subsequent calls to retrieve
the next 200, etc.?

On Tue, Jul 23, 2019 at 10:52 AM Majewski, Steven Dennis (sdm7g) <
sdm7g at virginia.edu> wrote:

> I believe the rationale of the waypoints was that initially, it was
> expected that resource children/ archival objects would fall into a more
> balanced tree structure, but it turned out that there were many flat
> hierarchies with hundreds of top level children, and getting all of the
> children at once was not working very efficiently. So with they waypoint
> calls, you may only be getting some of the children, but the display can
> start populating the tree display while making additional calls for the
> rest.
>
> I may have some postman examples and internal notes around somewhere: I’ll
> see what I can dig out.
>
> — Steve.
>
>
> On Jul 23, 2019, at 9:05 AM, Trevor Thornton <trthorn2 at ncsu.edu> wrote:
>
> Hi everybody-
>
> I'm building a service using these API endpoints (or I think I am):
> [:GET] /repositories/:repo_id/resources/:id/tree/root
> <http://archivesspace.github.io/archivesspace/api/#fetch-tree-information-for-the-top-level-resource-record>
> [:GET] /repositories/:repo_id/resources/:id/tree/node
> <http://archivesspace.github.io/archivesspace/api/#fetch-tree-information-for-an-archival-object-record-within-a-tree>
>
> These incorporate the concept of "waypoints", which I admit that I'm not
> familiar with in this context, and it isn't explained very well in the
> documentation. This is what I have to work with (these are elements
> included in the API response):
>
>    - child_count – the number of immediate children
>    - waypoints – the number of “waypoints” those children are grouped into
>    - waypoint_size – the number of children in each waypoint
>    - precomputed_waypoints – a collection of arrays (keyed on child URI)
>    in the same format as returned by the ’/waypoint’ endpoint. Since a fetch
>    for a given node is almost always followed by a fetch of the first
>    waypoint, using the information in this structure can save a backend call.
>
> Can anyone explain what exactly waypoints are and how they are different
> from children? In the examples I've seen, the "precomputed_waypoints"
> element in the response looks like a convoluted way (an array value of the
> lone element in an object, which is itself the value of the lone element in
> another object) to provide the children nodes of the given node (or root).
> What's the difference?
>
> Thanks,
> Trevor
>
> --
> Trevor Thornton
> Applications Developer, Digital Library Initiatives
> North Carolina State University Libraries
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-- 
Trevor Thornton
Applications Developer, Digital Library Initiatives
North Carolina State University Libraries
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