Support token modifier ':of-type'

[JohnTimm]

From http://hl7.org/fhir/search.html#token:

:of-type The search parameter has the format system|code|value, where the system and code refer to a Identifier.type.coding.system and .code, and match if any of the type codes match. All 3 parts must be present

From Team discussion:

1. Must look at extracting the parameter values and supporting the identifiers (token,code,system)
2. Update logic to support search using those extracted values when of-type is used

[tbieste]

Since system + code + value must be extracted together, I don't think this can using the existing _TOKEN_VALUES_V table/view, so may require a schema change.

[lmsurpre]

I think we should be able to get this one without a schema change. Two different ideas:

A. Since the spec requires users of of-type to always query with all 3 components, we should be able to combine the Identifier.type system+code together into one string and use that as the "system" for a token value. The one concern there is accidentally exceeding our column length limit, but I think it would be fine (if it exceeds the limit, you just can't search on that field).

B. Store the 3-tuple via an internal-only "composite parameter".
The parameter could be made of a couple components (both of type token): the first could have the system+code of the type and the second could have a default system and the identifier value as the code.

A worked example for B:
consider a Patient with an identifier that has 2 types:

Patient
Identifier
  Type 
    * mysystem|PI
    * yoursystem|ZZ
  Value 123

We'd have an internal search parameter definition like this

ibm-internal-identifier-type-composite-<paramname>
  * ibm-identifier-type (token)
  * ibm-identifier-value (token) (always going to have the default system)

after extraction we'd have entries like this in PATIENT_TOKEN_VALUES:

param_code_id	system	value	comp_id
ibm-identifier-type	mysystem	PI	1
Ibm-identifier-value	null	123	1
ibm-identifier-type	yoursystem	ZZ	2
Ibm-identifier-value	null	123	2

Query comes in: Patient?identifier:of-type=mystem|PI|123

Interally re-written as: Patient?ibm-internal-identifier-type-composite-identifier=mystem|PI$123

[tbieste]

Even though option A would be quicker, option B feels like the correct way to do this. Putting system+code into a single system field feels like a stop-gap approach. Since ':of-type' is a modifier that is unique in that it basically treats the search parameter as a composite, I think special internal handling to treat it like a composite makes sense.
This can be done in 2 stages (in different PRs even across different sprints):

1. Extract the parameter values (as an internal composite).
2. Update search to handle ':of-type' to search for the internal composite.

[tbieste]

All right! I think I have the :of-type search (as internal composite search) working. Thanks for the suggestion on that!
The FHIR spec says “All 3 parts must be present”, and that’s it. But I wonder if consistency with how token normally works if fewer parts are provided would be nice. Otherwise, what, throw an error?

[prb112]

@JohnTimm Verified