Search Parameters

Ignixa implements comprehensive FHIR search with support for all standard search parameters plus extensible search via FHIR packages.

Package-Based Search Parameters

Beyond the base FHIR specification parameters, Ignixa can load additional SearchParameter definitions from installed FHIR packages (Implementation Guides). Packages can be installed via:

• MCP tools - Use install_fhir_package tool via AI assistants
• Configuration - Pre-load packages at startup (see MCP Server)

This enables:

• Implementation Guide parameters - US Core, AU Base, UK Core, etc.
• Custom SearchParameters - Define your own search parameters
• Custom resource types - Search parameters for StructureDefinitions with custom types

Configuration

Control how package search parameters are loaded:

{
  "SearchParameters": {
    "ConflictResolution": {
      "PackagePriorityOrder": ["hl7.fhir.us.core", "hl7.fhir.au.base"],
      "UseSemanticVersioning": true,
      "LogConflicts": true,
      "EagerLoadPackageSearchParameters": true
    }
  }
}

Setting	Description
PackagePriorityOrder	Priority when multiple packages define same parameter code
UseSemanticVersioning	Newer versions win when no explicit priority
EagerLoadPackageSearchParameters	Load all at startup vs. lazy per resource type

Basic Search

GET /Patient?family=Smith&given=John

Search Parameter Types

String

Case-insensitive, partial match:

GET /Patient?name=smi
GET /Patient?name:exact=Smith
GET /Patient?name:contains=mit

Modifier	Description
(none)	Starts with
:exact	Exact match (case-sensitive)
:contains	Contains substring

Token

Coded values with system/code:

# Code only
GET /Observation?code=29463-7

# System|code
GET /Observation?code=http://loinc.org|29463-7

# System only
GET /Observation?code=http://loinc.org|

# Text modifier
GET /Observation?code:text=body%20weight

Reference

Resource references:

# Relative reference
GET /Observation?subject=Patient/123

# Type specified
GET /Observation?subject:Patient=123

# Chaining
GET /Observation?subject.name=Smith

# Identifier
GET /Observation?subject:identifier=http://hospital.org|MRN123

Date/DateTime

Temporal comparisons:

GET /Observation?date=2024-01-15
GET /Observation?date=ge2024-01-01&date=lt2024-02-01
GET /Patient?birthdate=1990

Prefix	Meaning
eq	Equals (default)
ne	Not equals
lt	Less than
gt	Greater than
le	Less than or equal
ge	Greater than or equal
sa	Starts after
eb	Ends before

Number/Quantity

Numeric searches:

GET /Observation?value-quantity=gt100
GET /Observation?value-quantity=100||mg
GET /Observation?value-quantity=ge5.4|http://unitsofmeasure.org|mg

URI

URI matching:

GET /ValueSet?url=http://example.org/ValueSet/my-codes
GET /ValueSet?url:below=http://example.org/

Search Modifiers

Common Modifiers

Modifier	Applicable Types	Example
:missing	All	?birthdate:missing=true
:exact	String	?name:exact=Smith
:contains	String	?name:contains=mit
:text	Token	?code:text=weight
:not	Token	?status:not=cancelled
:above	Token, URI	`?code:above=http://snomed.info/sct
:below	Token, URI	`?code:below=http://snomed.info/sct
:identifier	Reference	?subject:identifier=MRN123
:of-type	Token	`?identifier:of-type=http://...

Chained Parameters

Search on referenced resource properties:

# Single chain
GET /Observation?subject.name=Smith

# Multiple chains
GET /Observation?subject.organization.name=Hospital

# Reverse chain
GET /Patient?_has:Observation:subject:code=29463-7

Include/Revinclude

Return related resources:

# Forward include
GET /Observation?_include=Observation:subject

# Recursive include
GET /Observation?_include:iterate=Observation:subject

# Reverse include
GET /Patient?_revinclude=Observation:subject

Paginated Includes

Control the number of included resources returned separately from primary matches:

# Limit primary results to 10, includes to 50
GET /Patient?_include=Patient:organization&_count=10&_includesCount=50

# Response contains:
# - Up to 10 patients (primary matches)
# - Up to 50 organizations (included resources)
# - "related" link with _includesContinuationToken if more includes exist

Parameter	Description
_includesCount	Maximum number of included resources per page (separate from _count)
_includesContinuationToken	Continuation token for fetching additional included resources

When _includesCount is specified:

• The Bundle will contain up to _count primary matches
• The Bundle will contain up to _includesCount included resources
• If more includes exist, a "related" link is added with _includesContinuationToken
• Use the $includes operation to fetch additional included resources

See $includes operation for details on fetching additional included resources.

Result Modifiers

Sorting

GET /Patient?_sort=birthdate
GET /Patient?_sort=-birthdate          # Descending
GET /Patient?_sort=family,given        # Multiple

Paging

GET /Patient?_count=50
GET /Patient?_count=50&_offset=100

Total Count

GET /Patient?_total=accurate    # Exact count
GET /Patient?_total=estimate    # Estimated
GET /Patient?_total=none        # No count

Summary

GET /Patient?_summary=true      # Summary only
GET /Patient?_summary=text      # Text narrative
GET /Patient?_summary=data      # Data only
GET /Patient?_summary=count     # Count only

Elements

GET /Patient?_elements=name,birthDate,gender

Composite Parameters

Multiple values in conjunction:

GET /Observation?component-code-value-quantity=http://loinc.org|8480-6$gt100

Special Search Parameters

_not-referenced - Finding Orphaned Resources

The _not-referenced parameter finds resources that are not referenced by any other resource. This is useful for:

• Data cleanup workflows
• Identifying orphaned resources after deletions
• Data quality audits
• Compliance reporting

Syntax:

# Find all patients not referenced by any resource
GET /Patient?_not-referenced=*:*

# Find patients not referenced by any Observation
GET /Patient?_not-referenced=Observation:*

# Find patients not referenced by Observation.subject specifically
GET /Patient?_not-referenced=Observation:subject

Patterns:

Pattern	Meaning
*:*	Not referenced by any resource via any reference path
{ResourceType}:*	Not referenced by the specified resource type via any path
{ResourceType}:{path}	Not referenced via the specific reference path

Implementation Notes:

• Uses LEFT ANTI-JOIN SQL pattern for optimal performance
• Only available with SQL storage provider (not in-memory)
• Compatible with Microsoft FHIR Server syntax

Example Use Cases:

# Find patients without any observations
GET /Patient?_not-referenced=Observation:subject

# Find practitioners not assigned to any organization
GET /Practitioner?_not-referenced=Organization:*

# Find all completely orphaned diagnostic reports
GET /DiagnosticReport?_not-referenced=*:*

Batch Search

Search via POST with _search:

POST /Patient/_search
Content-Type: application/x-www-form-urlencoded

family=Smith&given=John

Search in Bundles

{
  "resourceType": "Bundle",
  "type": "batch",
  "entry": [{
    "request": {
      "method": "GET",
      "url": "Patient?family=Smith"
    }
  }]
}

Performance Tips

1. Use indexed parameters - Search on indexed fields for best performance
2. Limit results - Use _count to limit page size
3. Avoid wildcards - Avoid leading wildcards in string searches
4. Chain sparingly - Deep chains impact performance

Related Documentation

• Supported Resources
• Operations