Index missing search parameter (: missing)

When enabled, the : missing modifier can be used on a SearchParameter to find resources where that search parameter has found (or not found) any data in the given resource.

This feature defaults to: Disabled

Parameter name: enable_index_missing_fields

For example, take the Patient:birthdate search parameter, which indexes the value of Patient.birthDate. The following URL finds all patients having a birthdate:

Request: Search query for all patients with a birth date

Request: Search query for all patients without a birth date

Indexing for missing search parameters can add a great deal of extra index space, and slow down write operations on servers with many enabled search parameters. This feature is therefore disabled by default and must be specifically enabled if it is needed.