Modified Date is needed as sorting parameter for all FHIR resources

[khyativyasargus]

Describe the bug
Currently while querying resources from SDC , sort() method is available which can be used to get sorted data specially while we want to query resources with pagination, but currently modified date is stored only in meta data , not available for sort method parameter.

Component
Engine library

To Reproduce
Steps to reproduce the behavior:

1. Go to PatientListViewModel file in demo app
2. check getSearchResults method to get Patient resource list
3. sort(Patient.GIVEN, Order.ASCENDING) method is used in that method which is available at query level sorting
4. But when you check other available sorting parameters for Patient as GIVEN, Modified date can not be found which is needed in some cases for example, while we want to fetch last modified patients at top!
5. Same applies on all the resources

Expected behavior
For sort(Patient.GIVEN, Order.ASCENDING), Modified date should be available as well,

@jingtang10

[aditya-07]

@khyativyasargus Is the expectation to sort by the server assigned lastUpdated date or the local lastUpdated ?

[khyativyasargus]

@aditya-07 local assigned lastUpdated is needed

[santosh-pingle]

@khyativyasargus is it okay to change component from sdc library to engine library?

[khyativyasargus]

@santosh-pingle can you provide more context on this?
cc @jingtang10 @aditya-07

[santosh-pingle]

@santosh-pingle can you provide more context on this? cc @jingtang10 @aditya-07

@khyativyasargus
I intended to remove the SDC library from the component in the description of the issue. You can ignore it now, as I have updated the corresponding change. thanks!

[khyativyasargus]

@santosh-pingle Okay got it. Thanks!

[jingtang10]

As we don't store the local last updated timestamp, we will need to start storing it when we update resources locally.

Options:

1. use the meta element's last updated timestamp locally
2. add a new db column in resources table
3. same as 2 but add a new meta table which includes last updated timestamp
4. add a new default custom index in the date index table for all resources by default

Comparison:

	Update resource meta data	New column in resource table	New meta data table	New custom index
DB change	✅ No db change	⛔️ Need db change	⛔️ Need db change	✅ No db change
Preserve server last updated	⛔️ No	✅ Yes	✅ Yes	✅ Yes

So it seems like first we need to make a decision about if we want to overwrite server-side last updated timestamp.

[aditya-07]

@jingtang10 Another option could be to same as 4 but add a custom search parameter exclusively for local_lastUpdated . That way, we won't have to do a DB change and we can preserve server lastUpdated as well.

[aditya-07]

@omarismail94 @khyativyasargus @joiskash @ellykits @ekigamba Do you have any inputs or thoughts about the options listed above?

[khyativyasargus]

@aditya-07 I agree with your option as in metadata lastUpdated is already present and currently we are using that only to do sorting, altough for pagination query custom parameter is required so yes it can work with your approach!

Just one question is lastUpdated stored in metadata server_lastUpdated or local_lastUpdated ?