Search Operations

A search operation the allows to fetch resources, filtering them by supplied parameters. The parameters are a series of name=[value] pairs. The syntax for Read and Search is described here.

Parameters can be encoded in the URL in case of a search by GET method:

GET [base]/[type]?name=value&...{&_format=[mime-type]}}

POST  [base]/[type]/_search{?[parameters]{&_format=[mime-type]}}

The response to any search operation is always a list of resources in a Bundle or an Operation Outcome.

Supported global search parameters

The following parameters apply to all resources:

Supported search parameter types

Each search parameter is defined by a type that specifies how the search parameter behaves. These are the defined parameter types:

Support of modifiers/prefixes for number/date search parameter type

Support of modifiers/prefixes for string search parameter type

Support of modifiers/prefixes for token search parameter type

Support of modifiers/prefixes for reference search parameter type

Support of modifiers/prefixes for uri search parameter type

Dynamic search

Search in the Kodjin FHIR Server is dynamic. In order to enable search on some new parameter, the SearchParameter resource must be added via API. The Elasticsearch index should also be configured.

Pagination

Search in Kodjin supports two types of pagination:

• offset pagination (with skip or page parameters)
• cursor pagination

curl --location --request GET 'https://demo.kodjin.com/fhir/Coverage' \
--header 'Prefer: pagination=offset-skip'

curl --location --request GET 'https://demo.kodjin.com/fhir/Coverage' \
--header 'Prefer: pagination=offset-page'

curl --location --request GET 'https://demo.kodjin.com/fhir/Coverage?_count=3' \
--header 'Prefer: pagination=cursor'

Handling errors

Kodjin will not return an error if a parameter refers to a non-existent resource, e.g. GET [base]/Observation?subject=101, where "101" does not exist, or to an unknown code, e.g. GET [base]/Observation?code=loinc|1234-1, where the LOINC code "1234-1" is not known to the server. The response will be an empty search bundle.

Kodjin will return an error if it receives parameters from the client that it does not recognize, or parameters it recognizes but does not support (either in general, or for a specific search).

By default, the Kodjin FHIR Server ignores unknown or unsupported parameters for the following reasons: various HTTP stacks and proxies may add parameters that aren't under the control of the client.

Clients can specify how the server should behave by using the prefer header: -Prefer: handling=strict: Client requests that the server return an error for any unknown or unsupported parameter -Prefer: handling=lenient: Client requests that the server ignore any unknown or unsupported parameter.

```
{
    "resourceType": "OperationOutcome",
    "issue": [
        {
            "severity": "error",
            "code": "not-found",
            "details": {
                "text": "Unknown query param: test"
            }
        }
    ]
}
```

```
{
            "severity": "warning",
            "code": "value",
            "expression": [
                "Patient.name[0].text"
            ],
            "details": {
                "text": "Search on strings greater than 8000 symbols is not supported"
            }
        }
```