Pagination support

[bwalsh]

Thanks for a great project. Enjoying working with it.

Unless I've missed it, I don't see support for:

• https://www.hl7.org/fhir/http.html#paging
• https://www.hl7.org/fhir/search.html#count

Is this correct ?

[bwalsh]

A few more experiments reveals support for _count: just add it like any other parameter.

studies = [s for s in rs.ResearchStudy.where(struct={'_count':'1000'}).perform_resources(smart.server)]

[bwalsh]

Leaving this here in case it helps someone.

For our use case, we patched the underlying FHIRSearch.perform class to dispatch the search to multiple endpoints.
Note: the caller will need to formulate the list of api_bases
Pagination: The patch includes code to follow link results until all results are returned.

[ebrahimebrahim]

The comments here were very helpful for my project, thank you @bwalsh .

• Including the _count parameter in the search struct is easy and works great. Thanks for pointing this out.
• Paging can be be used manually by getting the bundle for your search via perform and then using the links in there to find the urls for the previous and next pages. In the case of the fhir server I was working with, the link to the next page showed up with the property "relation": "next". To follow the url, you can do smart.server.request_json(<url for next page>).

[anmolbhatia05]

@bwalsh @ebrahimebrahim Super helpful comments, thanks!

[bwalsh]

@anmolbhatia05 @ebrahimebrahim glad it helped

[enkaell]

I have some reservations about the current approach. We are potentially sacrificing runtime efficiency by transitioning from working with fhirclient.models.bundle.Bundle to a standard dictionary. This requires us to convert the Bundle into a dictionary or vice versa. As you can observe from my example:

bundle = Patient.where(struct={'_count': b'500'}).perform(smart.server)

bundle = smart.server.request_json(bundle.link[0].url)

while page := [page for page in bundle["link"] if "next" in page["relation"]]:
    page = smart.server.request_json(page[0]["url"])
    bundle = page

I am iterating over all pages in bundle by next link. I think there's should be another solution, otherwise raw requests are simpler and faster.