Support token modifier ':text'

[lmsurpre]

from https://www.hl7.org/fhir/R4/search.html#token:

The search parameter is processed as a string that searches text associated with the code/value - either CodeableConcept.text, Coding.display, or Identifier.type.text. In this case, the search functions as a normal string search

Note: by "normal string search" I assume they mean it should be a "starts-with" and "case-insensitive" match.

example:

Search for any Condition with a code that has a text "headache" associated with it (either in the text, or a display)
GET [base]/Condition?code:text=headache |

[lmsurpre]

I don't believe we even index these values today and it could be expensive (lots of new string values in our STR_VALUES tables).

No need to store it in original casing AND normalized casing like we do for other strings because you can't use an exact modifier with it. Will be cheaper to store it in the token_values tables in normalized/lowercase form and have special query logic to support the starts-with aspect.

There is a different issue for searching longer / more sophisticated text search: #481

[michaelwschroeder]

Running against my local server with the latest codebase, I have performed token searches using the :text modifier against multiple fields and resources and have verified:

• CodeableConcept.text and Coding.display fields have been indexed properly
• search against TOKEN search parameters referencing those fields is case-insensitive and correct results are returned.