Stream: implementers
Topic: Server Sort Support?
John Silva (Jun 11 2020 at 20:51):
How does FHIR server indicate which sort options it supports? Is this part of the metadata/CapabilityStatement? (I realize that the _sort options use the same names as the search options but how does a FHIR client know which sort options a server supports --- or is this even specified?)
Lloyd McKenzie (Jun 11 2020 at 22:14):
I think the answer is that there's no way to declare this right now. @Grahame Grieve @James Agnew ?
Grahame Grieve (Jun 11 2020 at 22:17):
I think so
John Silva (Jun 12 2020 at 02:04):
Also related to this is how can paging work if the sorting isn't known? I suppose that the FHIR server could (or must support _lastUpdated) as a sort mechanism so it has a consistent way to page through data. (even with _lastUpdated there could be data changes in between the time the client requests page 1, page 2, etc.)
Grahame Grieve (Jun 12 2020 at 02:05):
we've said that it's up to the server how to handle paging through data that might change
Grahame Grieve (Jun 12 2020 at 02:06):
if you really care about keeping up with out missing stuff, you can't depend on search - you have to use subscription or history
John Silva (Jun 12 2020 at 09:59):
So if there's no way for a FHIR server to "declare this" are the FHIR specs silent about how a server should (must?) support sort options? Is there a requirement to at least support _lastUpdated ?
I see now what Grahame was referring to w.r.t. paging:
"Note: It is at the discretion of the search engine as to how to handle ongoing updates to the resources while the search is proceeding.
Note: The combination of _sort and _count can be used to return only the latest resource that meets a particular criteria - set the criteria, and then sort by date in descending order, with _count=1. This way, the last matching resource will be returned."
I guess this leaves the sorting up to middleware or UI layers if sort order is important for business use cases.
Lloyd McKenzie (Jun 12 2020 at 14:03):
Servers don't have to support sort at all - any more than they have to support any search capabilities. We're looking at how to allow CapabilityStatement to support declaring all sorts of nuanced conformance expectations. I suspect this requirement will end up getting handled there.
Last updated: Apr 12 2022 at 19:14 UTC
