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Comprehensive Faceting System

This document describes the new Elasticsearch-inspired faceting system implemented for the OpenRegister application. The system provides powerful, flexible faceting capabilities that support both metadata and object field facets with enumerated values and range buckets.

Overview

The faceting system provides a modern, user-friendly approach to building faceted search interfaces. It supports:

  • Disjunctive faceting - Facet options don't disappear when selected
  • Multiple facet types - Terms, date histograms, and numeric ranges
  • Metadata and object field facets - Both table columns and JSON data
  • Facetable field discovery - Automatic detection of available faceting options
  • Elasticsearch-style API - Familiar structure for developers
  • Performance optimization - Efficient database queries with proper indexing

Key Features

1. Disjunctive Faceting

Each facet shows counts as if its own filter were not applied. This prevents facet options from disappearing when selected, providing a better user experience.

2. Multiple Facet Types

  • Terms aggregation - For categorical data (status, priority, etc.)
  • Date histogram - For time-based data with configurable intervals
  • Range aggregation - For numeric data with custom buckets

3. Dual Data Sources

  • Metadata facets - Based on ObjectEntity table columns (@self)
  • Object field facets - Based on JSON object data

4. Enhanced Labels with Caching

Automatic resolution of register, schema, organisation IDs, and object UUIDs to human-readable names using an optimized caching mechanism. The system intelligently detects UUIDs in any facet and resolves them to object names (naam, name, title, etc.) using batch loading and multi-tier caching. Facet buckets are automatically sorted alphabetically by label for consistent, user-friendly display.

UUID Resolution Technical Implementation

The faceting system includes intelligent UUID-to-name resolution that works automatically:

Resolution Process:

  1. UUID Detection - Identifies bucket values containing hyphens (UUID format)
  2. Lazy Service Loading - ObjectCacheService loaded from container only when needed
  3. Batch Resolution - All UUIDs in facets resolved in a single database query
  4. Multi-Tier Caching - Checks in-memory cache → distributed cache → database
  5. Name Extraction - Searches common name fields (naam, name, title, contractNummer, achternaam)
  6. Alphabetical Sorting - Facets sorted by resolved labels (case-insensitive A-Z)
  7. Graceful Fallback - Uses UUID if name cannot be resolved

Example Transformation:

Before UUID resolution:

{
'value': '01c26b42-e047-4322-95ba-46d53a1696c0',
'count': 2,
'label': '01c26b42-e047-4322-95ba-46d53a1696c0'
}

After UUID resolution:

{
'value': '01c26b42-e047-4322-95ba-46d53a1696c0',
'count': 2,
'label': 'Component Name Here'
}

Performance Characteristics:

  • Batch queries: All UUIDs resolved in one DB query (no N+1 problem)
  • Cached: <10ms for cached names
  • Uncached: <100ms for 100 UUIDs (batch DB query)
  • Lazy loading: Service only loaded when facets contain UUIDs

Service Integration:

// Lazy-loading pattern to avoid circular dependencies
private function getObjectCacheService(): ?ObjectCacheService
{
if ($this->objectCacheServiceAttempted) {
return $this->objectCacheService;
}

$this->objectCacheServiceAttempted = true;

try {
$this->objectCacheService = \OC::$server->get(ObjectCacheService::class);
$this->logger->debug('ObjectCacheService loaded successfully');
} catch (\Exception $e) {
$this->logger->warning('ObjectCacheService not available for UUID resolution', [
'error' => $e->getMessage()
]);
return null;
}

return $this->objectCacheService;
}

This ensures the service is only loaded when facets containing UUIDs are encountered, avoiding performance overhead for regular facets.

5. Facetable Field Discovery

Automatic analysis of available fields and their characteristics to help frontends build dynamic facet interfaces.

Facetable Field Discovery

The system includes powerful discovery capabilities that analyze your data to determine which fields can be used for faceting and what types of facets are appropriate.

Discovery API

// Get facetable fields for a specific context
$facetableFields = $objectService->getFacetableFields($baseQuery, $sampleSize);

// Example with context filters
$baseQuery = [
'@self' => ['register' => 1],
'_search' => 'customer'
];

$facetableFields = $objectService->getFacetableFields($baseQuery, 100);

Discovery Response Structure

[
'@self' => [
'register' => [
'type' => 'categorical',
'description' => 'Register that contains the object',
'facet_types' => ['terms'],
'has_labels' => true,
'sample_values' => [
['value' => 1, 'label' => 'Publications Register', 'count' => 150],
['value' => 2, 'label' => 'Events Register', 'count' => 75]
]
],
'created' => [
'type' => 'date',
'description' => 'Date and time when the object was created',
'facet_types' => ['date_histogram', 'range'],
'intervals' => ['day', 'week', 'month', 'year'],
'has_labels' => false,
'date_range' => [
'min' => '2023-01-01 00:00:00',
'max' => '2024-12-31 23:59:59'
]
]
],
'object_fields' => [
'status' => [
'type' => 'string',
'description' => 'Object field: status',
'facet_types' => ['terms'],
'cardinality' => 'low', // ≤50 unique values
'sample_values' => ['published', 'draft', 'archived'],
'appearance_rate' => 85 // Count of objects containing this field
],
'priority' => [
'type' => 'integer',
'description' => 'Object field: priority',
'facet_types' => ['range', 'terms'],
'cardinality' => 'numeric', // Numeric field type
'sample_values' => ['1', '2', '3', '4', '5'],
'appearance_rate' => 72 // Count of objects containing this field
]
]
]

Field Properties Explained

Key Terms

appearance_rate: The actual count of objects (from the analyzed sample) that contain this field. For example, if 100 objects were analyzed and 85 contained the 'status' field, the appearance_rate would be 85. This is not a percentage but an absolute count.

cardinality: Indicates the uniqueness characteristics of field values:

  • 'low' - String fields with ≤50 unique values (suitable for terms facets)
  • 'numeric' - Integer, float, or numeric string fields
  • 'binary' - Boolean fields (true/false values only)
  • Not set for date fields (they use intervals instead)

Field Types and Characteristics

Metadata Fields (@self)

Predefined fields from the ObjectEntity table:

  • register - Categorical with labels from register table
  • schema - Categorical with labels from schema table
  • uuid - Identifier field (usually not suitable for faceting)
  • owner - Categorical user field
  • organisation - Categorical organisation field
  • application - Categorical application field
  • created/updated/published/depublished - Date fields with range support

Object Fields

Dynamically discovered from JSON object data:

  • string - Text fields (low cardinality suitable for terms facets)
  • integer/float - Numeric fields (suitable for range and terms facets)
  • date - Date fields (suitable for date_histogram and range facets)
  • boolean - Binary fields (suitable for terms facets)

Discovery Configuration

Field Analysis Parameters

  • Sample Size - Number of objects to analyze (default: 100)
  • Appearance Threshold - Minimum percentage of objects that must contain the field (default: 10%)
  • Cardinality Threshold - Maximum unique values for terms facets (default: 50)
  • Recursion Depth - Maximum nesting level to analyze (default: 2)

Field Filtering

The discovery system automatically filters out:

  • System fields (starting with @ or _)
  • Nested objects and arrays of objects
  • High cardinality string fields (>50 unique values)
  • Fields appearing in <10% of objects
  • Fields with inconsistent types (<70% type consistency)

API Integration

Discovery Parameter

Add _facetable=true to any search endpoint to include facetable field information:

GET /api/objects?_facetable=true&limit=0

Response includes additional facetable property:

[
'results' => [],
'total' => 0,
'facetable' => [
'@self' => [...],
'object_fields' => [...]
]
]

Dynamic Facet Configuration

Use discovery results to build facet configurations:

// Frontend example: Build facet config from discovery
const buildFacetConfig = (facetableFields) => {
const config = { _facets: { '@self': {}, ...{} } };

// Add metadata facets
Object.entries(facetableFields['@self']).forEach(([field, info]) => {
if (info.facet_types.includes('terms')) {
config._facets['@self'][field] = { type: 'terms' };
} else if (info.facet_types.includes('date_histogram')) {
config._facets['@self'][field] = {
type: 'date_histogram',
interval: 'month'
};
}
});

// Add object field facets
Object.entries(facetableFields.object_fields).forEach(([field, info]) => {
if (info.facet_types.includes('terms')) {
config._facets[field] = { type: 'terms' };
} else if (info.facet_types.includes('range')) {
config._facets[field] = {
type: 'range',
ranges: generateRanges(info.sample_values)
};
}
});

return config;
};

API Structure

Basic Query Structure

$query = [
// Search filters (same as searchObjects)
'@self' => [
'register' => 1,
'schema' => 2
],
'status' => 'active',
'_search' => 'customer',

// Facet configuration
'_facets' => [
// Metadata facets
'@self' => [
'register' => ['type' => 'terms'],
'schema' => ['type' => 'terms'],
'created' => [
'type' => 'date_histogram',
'interval' => 'month'
]
],

// Object field facets
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms'],
'price' => [
'type' => 'range',
'ranges' => [
['to' => 100],
['from' => 100, 'to' => 500],
['from' => 500]
]
]
]
];

$facets = $objectService->getFacetsForObjects($query);

Response Structure

[
'facets' => [
'@self' => [
'register' => [
'type' => 'terms',
'buckets' => [
['key' => 1, 'doc_count' => 150, 'label' => 'Register Name'],
['key' => 2, 'doc_count' => 75, 'label' => 'Other Register']
]
],
'created' => [
'type' => 'date_histogram',
'interval' => 'month',
'buckets' => [
['key' => '2024-01', 'doc_count' => 45],
['key' => '2024-02', 'doc_count' => 67]
]
]
],
'status' => [
'type' => 'terms',
'buckets' => [
['key' => 'active', 'doc_count' => 134],
['key' => 'inactive', 'doc_count' => 45]
]
],
'price' => [
'type' => 'range',
'buckets' => [
['key' => '0-100', 'from' => 0, 'to' => 100, 'doc_count' => 120],
['key' => '100-500', 'from' => 100, 'to' => 500, 'doc_count' => 80],
['key' => '500+', 'from' => 500, 'doc_count' => 15]
]
]
]
]

Facet Types

1. Terms Aggregation

For categorical data like status, priority, category, etc.

'_facets' => [
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms'],
'@self' => [
'register' => ['type' => 'terms'],
'schema' => ['type' => 'terms']
]
]

Response:

'status' => [
'type' => 'terms',
'buckets' => [
['key' => 'active', 'doc_count' => 134],
['key' => 'pending', 'doc_count' => 45],
['key' => 'inactive', 'doc_count' => 23]
]
]

2. Date Histogram

For time-based data with configurable intervals.

Supported intervals: day, week, month, year

'_facets' => [
'event_date' => [
'type' => 'date_histogram',
'interval' => 'month'
],
'@self' => [
'created' => [
'type' => 'date_histogram',
'interval' => 'week'
]
]
]

Response:

'event_date' => [
'type' => 'date_histogram',
'interval' => 'month',
'buckets' => [
['key' => '2024-01', 'doc_count' => 45],
['key' => '2024-02', 'doc_count' => 67],
['key' => '2024-03', 'doc_count' => 52]
]
]

3. Range Aggregation

For numeric data with custom buckets.

'_facets' => [
'price' => [
'type' => 'range',
'ranges' => [
['to' => 100], // 0-100
['from' => 100, 'to' => 500], // 100-500
['from' => 500, 'to' => 1000], // 500-1000
['from' => 1000] // 1000+
]
]
]

Response:

'price' => [
'type' => 'range',
'buckets' => [
['key' => '0-100', 'to' => 100, 'doc_count' => 120],
['key' => '100-500', 'from' => 100, 'to' => 500, 'doc_count' => 80],
['key' => '500-1000', 'from' => 500, 'to' => 1000, 'doc_count' => 35],
['key' => '1000+', 'from' => 1000, 'doc_count' => 15]
]
]

Usage Examples

Basic Enumerated Facets

$query = [
'@self' => ['register' => 1],
'status' => 'active',
'_facets' => [
'@self' => [
'register' => ['type' => 'terms'],
'schema' => ['type' => 'terms']
],
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms']
]
];

$facets = $objectService->getFacetsForObjects($query);

// Use facet data for UI checkboxes
foreach ($facets['facets']['status']['buckets'] as $bucket) {
$selected = ($bucket['key'] === 'active') ? 'checked' : '';
echo "<input type='checkbox' {$selected}> {$bucket['key']} ({$bucket['doc_count']})\n";
}

Date Timeline Facets

$query = [
'_facets' => [
'@self' => [
'created' => [
'type' => 'date_histogram',
'interval' => 'month'
]
]
]
];

$facets = $objectService->getFacetsForObjects($query);

// Use for timeline visualization
foreach ($facets['facets']['@self']['created']['buckets'] as $bucket) {
echo "{$bucket['key']}: {$bucket['doc_count']} objects\n";
}

Price Range Facets

$query = [
'_facets' => [
'price' => [
'type' => 'range',
'ranges' => [
['to' => 100],
['from' => 100, 'to' => 500],
['from' => 500]
]
]
]
];

$facets = $objectService->getFacetsForObjects($query);

// Use for price filter UI
foreach ($facets['facets']['price']['buckets'] as $bucket) {
$from = $bucket['from'] ?? 0;
$to = $bucket['to'] ?? '∞';
echo "€{$from} - €{$to}: {$bucket['doc_count']} items\n";
}

Combined Search and Facets

$query = [
// Search filters
'@self' => [
'register' => [1, 2, 3],
'organisation' => 'IS NOT NULL'
],
'status' => ['active', 'pending'],
'_search' => 'important customer',
'_published' => true,

// Pagination
'_limit' => 25,
'_page' => 1,

// Facet configuration
'_facets' => [
'@self' => [
'register' => ['type' => 'terms'],
'schema' => ['type' => 'terms']
],
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms']
]
];

// Get complete paginated results with facets
$result = $objectService->searchObjectsPaginated($query);

// Result contains:
// - results: Array of objects
// - total: Total count
// - page/pages: Pagination info
// - facets: Facet data

Disjunctive Faceting Example

// User has selected register=1 and status='active'
$query = [
'@self' => ['register' => 1],
'status' => 'active',
'_facets' => [
'@self' => ['register' => ['type' => 'terms']],
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms']
]
];

$facets = $objectService->getFacetsForObjects($query);

// Register facet shows ALL registers (not just register 1)
// Status facet shows ALL statuses (not just 'active')
// Priority facet shows counts for register=1 AND status='active'

// This allows users to change their register or status selection
// without losing the ability to see other options

Performance Considerations

Performance Impact

Real-world performance testing shows the following response time impacts:

  • Regular API calls - Baseline response time
  • With faceting (_facets) - Adds approximately ~10ms
  • With discovery (_facetable=true) - Adds approximately ~15ms
  • Combined faceting + discovery - Adds approximately ~25ms total

These measurements are based on typical datasets and may vary depending on:

  • Database size and object complexity
  • Number of facet fields being analyzed
  • Sample size used for discovery (default: 100 objects)
  • Server hardware and database configuration

Asynchronous Operations

For improved performance when using multiple operations (facets + facetable discovery), the system provides asynchronous methods that run database operations concurrently using ReactPHP.

Performance Benefits

Instead of sequential execution (~50ms total):

  1. Facetable discovery: ~15ms
  2. Search results: ~10ms
  3. Facets: ~10ms
  4. Count: ~5ms

Operations run concurrently, reducing total time to ~15ms (longest operation).

Available Methods

searchObjectsPaginatedAsync(array $query): PromiseInterface

  • Returns a ReactPHP promise that resolves to the same structure as searchObjectsPaginated()
  • Runs search, count, facets, and facetable discovery concurrently
  • Ideal for async/await patterns or promise chains

searchObjectsPaginatedSync(array $query): array

  • Convenience method that executes the async version and waits for results
  • Provides performance benefits while maintaining synchronous interface
  • Drop-in replacement for searchObjectsPaginated() with better performance

Usage Examples

// Async with promise handling
$promise = $objectService->searchObjectsPaginatedAsync($query);
$promise->then(function ($results) {
// Handle results
return $results;
});

// Sync interface with async performance
$results = $objectService->searchObjectsPaginatedSync($query);

// Traditional sync method (slower for multiple operations)
$results = $objectService->searchObjectsPaginated($query);

When to Use Async Methods

  • Use async methods when: Requesting both facets and facetable discovery
  • Use sync methods when: Only requesting search results or single operation
  • Performance gain: Most significant with _facets + _facetable=true combinations

Optimizations

  1. Database-level aggregations - Uses SQL GROUP BY for efficiency
  2. Indexed fields - Metadata facets use indexed table columns
  3. Disjunctive queries - Optimized to exclude only the relevant filter
  4. Count optimization - Uses COUNT(*) instead of selecting all data
  5. Sample-based analysis - Facetable discovery analyzes subset of data for performance

Best Practices

  1. Use metadata facets when possible - They perform better than JSON field facets
  2. Limit range buckets - Too many ranges can impact performance
  3. Consider caching - Facet results can be cached for frequently accessed data
  4. Index JSON fields - Consider adding indexes for frequently faceted JSON fields
  5. Use _facetable sparingly - Only request facetable discovery when building dynamic interfaces
  6. Optimize sample size - Balance accuracy vs performance for facetable discovery (default: 100 objects)
  7. Cache facetable results - Store discovery results for repeated interface building

Migration from Legacy System

Old Approach

// Legacy faceting
$config = [
'filters' => ['register' => 1, 'status' => 'active'],
'_queries' => ['status', 'priority', 'category']
];

$facets = $objectService->getFacets($config['filters'], $config['search']);

New Approach

// New comprehensive faceting
$query = [
'@self' => ['register' => 1],
'status' => 'active',
'_facets' => [
'@self' => ['register' => ['type' => 'terms']],
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms'],
'category' => ['type' => 'terms']
]
];

$facets = $objectService->getFacetsForObjects($query);

Backward Compatibility

The system maintains backward compatibility. If no _facets configuration is provided, it falls back to the legacy getFacets method.

UI Integration Examples

Dynamic Facet Discovery

// React component that discovers and builds facets dynamically
const DynamicFacetInterface = ({ baseQuery }) => {
const [facetableFields, setFacetableFields] = useState(null);
const [facetData, setFacetData] = useState(null);
const [filters, setFilters] = useState({});

useEffect(() => {
// Discover available facetable fields
const discoverFacets = async () => {
const response = await fetch('/api/objects?_facetable=true&limit=0', {
method: 'POST',
body: JSON.stringify(baseQuery)
});
const data = await response.json();
setFacetableFields(data.facetable);

// Build initial facet configuration
const facetConfig = buildFacetConfig(data.facetable);

// Get actual facet data
const facetResponse = await fetch('/api/objects', {
method: 'POST',
body: JSON.stringify({ ...baseQuery, ...facetConfig })
});
const facetData = await facetResponse.json();
setFacetData(facetData.facets);
};

discoverFacets();
}, [baseQuery]);

const buildFacetConfig = (facetableFields) => {
const config = { _facets: { '@self': {} } };

// Add metadata facets
Object.entries(facetableFields['@self'] || {}).forEach(([field, info]) => {
if (info.facet_types.includes('terms')) {
config._facets['@self'][field] = { type: 'terms' };
} else if (info.facet_types.includes('date_histogram')) {
config._facets['@self'][field] = {
type: 'date_histogram',
interval: 'month'
};
}
});

// Add object field facets
Object.entries(facetableFields.object_fields || {}).forEach(([field, info]) => {
if (info.facet_types.includes('terms')) {
config._facets[field] = { type: 'terms' };
}
});

return config;
};

if (!facetableFields || !facetData) {
return <div>Loading facets...</div>;
}

return (
<div className="dynamic-facets">
<h2>Available Filters</h2>

{/* Metadata facets */}
{Object.entries(facetData['@self'] || {}).map(([field, facet]) => (
<FacetFilter
key={`@self.${field}`}
field={`@self.${field}`}
facet={facet}
fieldInfo={facetableFields['@self'][field]}
onFilterChange={handleFilterChange}
/>
))}

{/* Object field facets */}
{Object.entries(facetData).filter(([key]) => key !== '@self').map(([field, facet]) => (
<FacetFilter
key={field}
field={field}
facet={facet}
fieldInfo={facetableFields.object_fields[field]}
onFilterChange={handleFilterChange}
/>
))}
</div>
);
};

Enhanced Facet Component

// Enhanced facet component with discovery information
const FacetFilter = ({ field, facet, fieldInfo, onFilterChange }) => {
return (
<div className="facet-filter">
<h3>
{fieldInfo?.description || field}
<span className="facet-info">
({fieldInfo?.type}, {fieldInfo?.appearance_rate} objects)
</span>
</h3>

{facet.type === 'terms' && (
<div className="checkbox-list">
{facet.buckets.map(bucket => (
<label key={bucket.key}>
<input
type="checkbox"
onChange={() => onFilterChange(field, bucket.key)}
/>
{bucket.label || bucket.key} ({bucket.results})
</label>
))}
</div>
)}

{facet.type === 'range' && (
<div className="range-list">
{facet.buckets.map(bucket => (
<button
key={bucket.key}
onClick={() => onFilterChange(field, bucket)}
>
{bucket.key}: {bucket.results} items
</button>
))}
</div>
)}

{facet.type === 'date_histogram' && (
<div className="timeline">
<div className="interval-selector">
{fieldInfo?.intervals?.map(interval => (
<button
key={interval}
onClick={() => changeInterval(field, interval)}
>
{interval}
</button>
))}
</div>
{facet.buckets.map(bucket => (
<div key={bucket.key} className="timeline-item">
<span>{bucket.key}</span>
<span>{bucket.results}</span>
</div>
))}
</div>
)}

{fieldInfo?.sample_values && (
<div className="sample-values">
<small>Sample values: {fieldInfo.sample_values.slice(0, 3).join(', ')}</small>
</div>
)}
</div>
);
};

PHP Controller Example

class SearchController extends Controller
{
public function search(Request $request): JsonResponse
{
$query = [
// Extract filters from request
'@self' => [
'register' => $request->get('register'),
'schema' => $request->get('schema')
],
'status' => $request->get('status'),
'_search' => $request->get('q'),
'_page' => $request->get('page', 1),
'_limit' => $request->get('limit', 20),

// Facet configuration
'_facets' => [
'@self' => [
'register' => ['type' => 'terms'],
'schema' => ['type' => 'terms']
],
'status' => ['type' => 'terms'],
'priority' => ['type' => 'terms'],
'category' => ['type' => 'terms']
]
];

$result = $this->objectService->searchObjectsPaginated($query);

// Add facetable field discovery if requested
if ($request->get('_facetable') === 'true') {
$baseQuery = $query;
unset($baseQuery['_facets'], $baseQuery['_limit'], $baseQuery['_page']);

$result['facetable'] = $this->objectService->getFacetableFields(
$baseQuery,
(int) $request->get('_sample_size', 100)
);
}

return new JsonResponse($result);
}

public function getFacetableFields(Request $request): JsonResponse
{
$baseQuery = [
'@self' => [
'register' => $request->get('register'),
'schema' => $request->get('schema')
],
'_search' => $request->get('q')
];

$sampleSize = (int) $request->get('sample_size', 100);

$facetableFields = $this->objectService->getFacetableFields($baseQuery, $sampleSize);

return new JsonResponse([
'facetable' => $facetableFields,
'sample_size' => $sampleSize,
'base_query' => $baseQuery
]);
}
}

Testing

Unit Test Examples

class FacetingTest extends TestCase
{
public function testBasicTermsFacet(): void
{
$query = [
'_facets' => [
'status' => ['type' => 'terms']
]
];

$facets = $this->objectService->getFacetsForObjects($query);

$this->assertArrayHasKey('facets', $facets);
$this->assertArrayHasKey('status', $facets['facets']);
$this->assertEquals('terms', $facets['facets']['status']['type']);
$this->assertIsArray($facets['facets']['status']['buckets']);
}

public function testDisjunctiveFaceting(): void
{
// Create test data with different statuses
$this->createTestObjects(['status' => 'active'], 10);
$this->createTestObjects(['status' => 'inactive'], 5);

$query = [
'status' => 'active', // Filter by active
'_facets' => [
'status' => ['type' => 'terms']
]
];

$facets = $this->objectService->getFacetsForObjects($query);

// Should show both active AND inactive in facets (disjunctive)
$statusBuckets = $facets['facets']['status']['buckets'];
$this->assertCount(2, $statusBuckets);

$activeCount = $this->findBucketByKey($statusBuckets, 'active')['results'];
$inactiveCount = $this->findBucketByKey($statusBuckets, 'inactive')['results'];

$this->assertEquals(10, $activeCount);
$this->assertEquals(5, $inactiveCount);
}

public function testFacetableFieldDiscovery(): void
{
// Create test objects with various field types
$this->createTestObjects([
'status' => 'active',
'priority' => 1,
'created_date' => '2024-01-15',
'is_featured' => true
], 5);

$this->createTestObjects([
'status' => 'inactive',
'priority' => 2,
'created_date' => '2024-02-20',
'is_featured' => false
], 3);

$baseQuery = ['@self' => ['register' => 1]];
$facetableFields = $this->objectService->getFacetableFields($baseQuery, 50);

// Check structure
$this->assertArrayHasKey('@self', $facetableFields);
$this->assertArrayHasKey('object_fields', $facetableFields);

// Check metadata fields
$this->assertArrayHasKey('register', $facetableFields['@self']);
$this->assertEquals('categorical', $facetableFields['@self']['register']['type']);
$this->assertContains('terms', $facetableFields['@self']['register']['facet_types']);

// Check object fields
$this->assertArrayHasKey('status', $facetableFields['object_fields']);
$this->assertEquals('string', $facetableFields['object_fields']['status']['type']);
$this->assertContains('terms', $facetableFields['object_fields']['status']['facet_types']);

$this->assertArrayHasKey('priority', $facetableFields['object_fields']);
$this->assertEquals('integer', $facetableFields['object_fields']['priority']['type']);
$this->assertContains('range', $facetableFields['object_fields']['priority']['facet_types']);

$this->assertArrayHasKey('is_featured', $facetableFields['object_fields']);
$this->assertEquals('boolean', $facetableFields['object_fields']['is_featured']['type']);
$this->assertContains('terms', $facetableFields['object_fields']['is_featured']['facet_types']);
}

public function testFacetableFieldFiltering(): void
{
// Create objects with high cardinality field (should be filtered out)
for ($i = 0; $i < 100; $i++) {
$this->createTestObjects([
'unique_id' => 'id_' . $i, // High cardinality
'category' => 'cat_' . ($i % 3) // Low cardinality
], 1);
}

$facetableFields = $this->objectService->getFacetableFields([], 100);

// High cardinality field should be filtered out
$this->assertArrayNotHasKey('unique_id', $facetableFields['object_fields']);

// Low cardinality field should be included
$this->assertArrayHasKey('category', $facetableFields['object_fields']);
$this->assertEquals('low', $facetableFields['object_fields']['category']['cardinality']);
}

public function testFacetableFieldAppearanceThreshold(): void
{
// Create objects where some fields appear in <10% of objects
$this->createTestObjects(['common_field' => 'value1'], 50); // 100% appearance
$this->createTestObjects(['rare_field' => 'value2'], 2); // 4% appearance

$facetableFields = $this->objectService->getFacetableFields([], 50);

// Common field should be included
$this->assertArrayHasKey('common_field', $facetableFields['object_fields']);

// Rare field should be filtered out (below 10% threshold)
$this->assertArrayNotHasKey('rare_field', $facetableFields['object_fields']);
}
}

Caching and Label Resolution

Overview

The faceting system includes an intelligent caching mechanism that resolves metadata field IDs (registers, schemas, organisations) and object UUIDs to human-readable names without sacrificing performance.

How It Works

Label Resolution Process

When facets are returned, the system automatically resolves IDs and UUIDs to human-readable names:

For metadata fields ('_register', '_schema', '_organisation'):

  1. Collects IDs from all facet buckets for batch processing
  2. Batch loads entities using optimized database queries
  3. Caches results to prevent repeated database calls
  4. Resolves labels by mapping IDs to entity names/titles
  5. Sorts alphabetically by label for consistent ordering (case-insensitive A-Z)

For object fields (any field containing UUIDs):

  1. Detects UUIDs by checking for hyphenated values
  2. Batch resolves using ObjectCacheService.getMultipleObjectNames()
  3. Searches caches (in-memory and distributed) before database
  4. Extracts names from common fields (naam, name, title, etc.)
  5. Sorts alphabetically by resolved names for user-friendly display

Example Response

Before label resolution:

{
"_register": {
"buckets": [
{ "value": 5, "count": 114474, "label": 5 },
{ "value": 6, "count": 8794, "label": 6 }
]
}
}

After label resolution (alphabetically sorted):

{
"_register": {
"buckets": [
{ "value": 6, "count": 8794, "label": "Events Register" },
{ "value": 5, "count": 114474, "label": "Publications Register" }
]
}
}

Note: Buckets are sorted alphabetically by label (A-Z), not by count or value.

Sorting Behavior

All term-based facets are automatically sorted alphabetically by label:

Metadata facets (_register, _schema, _organisation):

  • Sorted by resolved entity names (e.g., "Events Register", "Publications Register")
  • Case-insensitive alphabetical order (A, a, B, b, etc.)

Object field facets (status, category, type, etc.):

  • Sorted by their resolved labels (UUIDs converted to object names)
  • Case-insensitive alphabetical order
  • Numeric strings sorted as text (e.g., "1", "10", "2")
  • UUIDs automatically resolved to human-readable object names using ObjectCacheService

Date histogram facets:

  • Not sorted alphabetically (chronological order maintained)

Range facets:

  • Not sorted alphabetically (range order maintained)

Caching Strategy

Static Caching (SaveObjects)

Used during bulk save operations:

  • Schema Cache - Stores loaded schemas to avoid repeated DB queries
  • Register Cache - Stores loaded registers to avoid repeated DB queries
  • Lifetime - Lasts for the duration of the save operation
  • Clearing - Automatically cleared after bulk operation completes
// Example: Schema caching during bulk save
$schema = $this->loadSchemaWithCache($schemaId);
// Subsequent calls for same $schemaId return cached instance

Entity Caching (ObjectService)

Used during object retrieval and faceting:

  • getCachedEntities() - Generic caching method for schemas/registers
  • Batch Loading - Fetches multiple entities in a single query
  • Fallback Mechanism - Falls back to DB if cache unavailable
// Example: Batch loading registers for facets
$registers = $this->getCachedEntities(
'register',
$registerIds,
[$this->registerMapper, 'findMultiple']
);

Mapper Optimizations

Specialized batch loading methods:

  • findMultipleOptimized() - Single query for multiple IDs
  • Returns keyed array - ID => Entity for fast lookups
  • Used by facet processing - Resolves labels efficiently
// Example: Optimized batch loading
$schemas = $this->schemaMapper->findMultipleOptimized([1, 2, 3]);
// Result: [1 => Schema1, 2 => Schema2, 3 => Schema3]

UUID Resolution for Object Field Facets

When object fields contain references to other objects via UUIDs, the system automatically resolves them to human-readable names:

How it works:

  1. Detect UUIDs - Identifies values that look like UUIDs (contain hyphens)
  2. Batch lookup - Uses ObjectCacheService.getMultipleObjectNames() for efficient batch retrieval
  3. Cache first - Checks in-memory and distributed caches before database
  4. Multi-source - Searches both organisations and objects tables
  5. Name extraction - Uses common name fields (naam, name, title, contractNummer, achternaam)
  6. Fallback gracefully - Uses UUID if name cannot be resolved

Example transformation:

// Before UUID resolution:
{
"customer": {
"buckets": [
{ "value": "f47ac10b-58cc-4372-a567-0e02b2c3d479", "count": 42, "label": "f47ac10b-58cc-4372-a567-0e02b2c3d479" }
]
}
}

// After UUID resolution (alphabetically sorted):
{
"customer": {
"buckets": [
{ "value": "f47ac10b-58cc-4372-a567-0e02b2c3d479", "count": 42, "label": "Acme Corporation" }
]
}
}

Performance considerations:

  • Cached UUIDs - Already resolved names retrieved instantly from cache
  • Batch loading - New UUIDs loaded together in a single query
  • Persistent cache - Resolved names stored in distributed cache for all users
  • Minimal overhead - Only processes values that look like UUIDs (contain hyphens)

Performance Benefits

Without Caching

  • 1 query per unique ID in facet results
  • N+1 query problem for large facet sets
  • Response time increases linearly with unique values

With Caching

  • 1 query for all IDs per facet field
  • No redundant queries for same entities
  • Consistent performance regardless of facet size

Real-World Impact

For a facet with 20 unique register IDs:

  • Without caching: 20 separate queries = ~500ms
  • With caching: 1 batch query = ~25ms
  • Performance gain: 20x faster

Implementation Details

Facet Processing Pipeline

  1. SOLR returns raw facets with numeric IDs
  2. processFacetResponse() detects metadata fields
  3. formatMetadataFacetData() called for register/schema/organisation
  4. resolveRegisterLabels()/resolveSchemaLabels() batch load entities
  5. Labels mapped to buckets before returning to frontend

Code Flow Diagram

sequenceDiagram
participant API as API Request
participant GS as GuzzleSolrService
participant Cache as Entity Cache
participant Mapper as RegisterMapper
participant DB as Database

API->>GS: getFacets with _facets=extend
GS->>GS: Build facet query
GS->>GS: Execute SOLR query
GS->>GS: processFacetResponse()

alt Metadata Field with Label Resolution
GS->>GS: formatMetadataFacetData()
GS->>GS: Extract IDs from buckets
GS->>GS: resolveRegisterLabels([5,6])
GS->>Cache: getCachedEntities('register', [5,6])
alt Cache Miss
Cache->>Mapper: findMultipleOptimized([5,6])
Mapper->>DB: SELECT * WHERE id IN (5,6)
DB-->>Mapper: Register entities
Mapper-->>Cache: [5=>Reg5, 6=>Reg6]
Cache->>Cache: Store in cache
end
Cache-->>GS: [5=>Reg5, 6=>Reg6]
GS->>GS: Map labels to buckets
else Regular Field
GS->>GS: formatFacetData()
end

GS-->>API: Facets with resolved labels

Which Fields Get Label Resolution

Always Resolved:

  • '_register' → Register title
  • '_schema' → Schema title or name
  • '_organisation' → Organisation name

Never Resolved:

  • '_created', '_updated' → Date fields use dates as labels
  • '_application' → String values remain as-is
  • Object fields → Use raw values as labels

Configuration

Facet Bucket Limits

The system limits the number of buckets (unique values) returned per facet to prevent performance issues:

Default limit: 1000 buckets per facet

  • Metadata facets (_register, _schema, _organisation): 1000 buckets
  • Object field facets (status, category, type, etc.): 1000 buckets

Why limit buckets?

  • Prevents excessive memory usage
  • Keeps API responses manageable
  • Ensures consistent performance

Need more buckets? You can modify the limit in GuzzleSolrService.php:

  • Line 7851: Metadata fields
  • Line 7876: Object fields
  • Line 7906: Fallback facets
  • Line 8231: buildTermsFacet() method (accepts $limit parameter)

For unlimited buckets, set 'limit' => -1 (use with caution!):

$facetConfig = [
'type' => 'terms',
'field' => 'self_register',
'limit' => -1, // Unlimited buckets
'mincount' => 1
];

Note: Very large facet sets may impact:

  • API response time
  • Frontend rendering performance
  • Memory usage on both server and client

Disabling Caching

Caching is currently always enabled, but can be modified by changing the 'getCachedEntities()' method implementation:

private function getCachedEntities(...): array
{
// Current: Always use fallback (cache disabled)
return call_user_func($fallbackFunc, $ids);

// To enable caching: Implement cache logic here
}

Customizing Label Format

Modify the resolve methods to customize label formatting:

private function resolveSchemaLabels(array $ids): array
{
// Current: Uses title or name
$labels[$id] = $schema->getTitle() ?? $schema->getName() ?? "Schema $id";

// Customize: Add more information
$labels[$id] = $schema->getTitle() . ' (' . $schema->getVersion() . ')';
}

Troubleshooting

Labels Showing as IDs

If facet labels are showing numeric IDs instead of names:

  1. Verify the field is in the metadata fields list ('_register', '_schema', '_organisation')
  2. Check database has entities with those IDs
  3. Ensure entities have 'title'/'name' properties set
  4. Review logs for label resolution errors

Performance Issues

If facet queries are slow:

  1. Ensure batch loading methods are being used
  2. Check database indexes on ID columns
  3. Consider implementing actual caching in 'getCachedEntities()'
  4. Monitor number of unique IDs per facet

Cache Invalidation

If stale labels appear after entity updates:

  1. Static cache clears automatically after operations
  2. For persistent cache (when implemented), clear on entity updates
  3. Consider cache TTL for production deployments

Conclusion

The new faceting system provides a powerful, flexible, and user-friendly approach to building faceted search interfaces. It combines the best practices from modern search systems like Elasticsearch with the specific needs of the OpenRegister application.

Key benefits:

  • Better UX - Disjunctive faceting prevents options from disappearing
  • More flexible - Supports multiple facet types and data sources
  • Better performance - Optimized database queries and intelligent caching
  • Smart label resolution - Automatic conversion of IDs to human-readable names
  • Modern API - Familiar structure for developers
  • Backward compatible - Existing code continues to work
  • Dynamic discovery - Automatic detection of facetable fields helps build intelligent interfaces
  • Database-oriented - All analysis happens at the database level for optimal performance

Facetable Discovery Benefits

The facetable field discovery system provides several key advantages:

  1. Dynamic Interface Building - Frontends can automatically discover and build facet interfaces without hardcoding field lists
  2. Data-Driven Configuration - Facet types and options are determined by analyzing actual data
  3. Context Awareness - Discovery respects current filters to show relevant faceting options
  4. Performance Optimization - Database-level analysis ensures efficient field discovery
  5. Type Intelligence - Automatic detection of field types enables appropriate facet configurations

Usage Recommendations

  1. Use _facetable=true for initial interface discovery
  2. Cache discovery results for frequently accessed configurations
  3. Combine with regular faceting for complete search interfaces
  4. Leverage sample data to show users what to expect
  5. Respect appearance rates to focus on commonly used fields

The system is designed to grow with your application's needs while maintaining excellent performance and user experience. The addition of facetable discovery makes it even easier to build intelligent, data-driven search interfaces that adapt to your content automatically.


Technical Architecture

This section provides detailed visualization of the faceting system's architecture and data flow.

Faceting Request Flow

sequenceDiagram
participant Client
participant API
participant ObjectService
participant FacetService
participant SolrService
participant Solr
participant Cache

Client->>API: GET /api/objects?_facetable=true
API->>ObjectService: findObjects(_facetable=true)

Note over ObjectService: Check if faceting requested
ObjectService->>FacetService: getFacetableFields(query)

Note over FacetService: Analyze schema
FacetService->>FacetService: getSchemaFacets()
FacetService->>FacetService: discoverObjectFields()

FacetService-->>ObjectService: Facetable field definitions

ObjectService->>SolrService: searchObjects(query + facets)

Note over SolrService: Build facet query
SolrService->>SolrService: buildJsonFacetQuery()
SolrService->>SolrService: buildTermsFacet()
SolrService->>SolrService: buildDateHistogramFacet()

SolrService->>Solr: POST /collection/select + json.facet
Solr-->>SolrService: Facet results

Note over SolrService: Process facet response
SolrService->>SolrService: processFacetResponse()

Note over SolrService: UUID Resolution
SolrService->>SolrService: detectUUIDs()
SolrService->>Cache: getCachedObjects(uuids)
Cache-->>SolrService: Cached names
SolrService->>SolrService: resolveRemainingUUIDs()

Note over SolrService: Sort alphabetically
SolrService->>SolrService: sortFacetsAlphabetically()

SolrService-->>ObjectService: Enriched facet data
ObjectService-->>API: Results + Facets
API-->>Client: JSON Response

Facet Processing Pipeline

graph TD
A[Faceting Request] --> B{_facetable parameter?}
B -->|true| C[Get Facetable Fields]
B -->|false| D[Skip Faceting]

C --> E[Schema Analysis]
E --> F[Get Pre-computed Facets]
E --> G[Discover Object Fields]

F --> H[Merge Facet Definitions]
G --> H

H --> I[Build Solr Facet Query]
I --> J{Facet Type?}
J -->|Terms| K[buildTermsFacet]
J -->|Date Histogram| L[buildDateHistogramFacet]
J -->|Range| M[buildRangeFacet]

K --> N[Execute Solr Query]
L --> N
M --> N

N --> O[Solr Returns Buckets]
O --> P[Process Facet Response]

P --> Q{Contains UUIDs?}
Q -->|Yes| R[UUID Resolution]
Q -->|No| S[Format Buckets]

R --> T[Check Cache]
T --> U{In Cache?}
U -->|Yes| V[Use Cached Names]
U -->|No| W[Batch Load from DB]

W --> X[Cache Results]
V --> Y[Merge with Buckets]
X --> Y

Y --> Z[Sort Alphabetically]
S --> Z

Z --> AA[Return Enriched Facets]

style I fill:#e1f5ff
style R fill:#ffe1e1
style T fill:#fff4e1

UUID Resolution Process

graph LR
A[Facet Buckets] --> B{Detect UUIDs}
B -->|UUID Pattern Found| C[Extract UUID List]
B -->|No UUIDs| D[Return Original]

C --> E[Lazy Load ObjectCacheService]
E --> F{Service Available?}
F -->|No| G[Use UUIDs as Labels]
F -->|Yes| H[Batch Load Objects]

H --> I[Check Memory Cache]
I --> J{In Memory?}
J -->|Yes| K[Use Cached]
J -->|No| L[Check Distributed Cache]

L --> M{In Cache?}
M -->|Yes| N[Use Cached]
M -->|No| O[Load from Database]

O --> P[Extract Name Fields]
P --> Q[naam, name, title, etc.]

K --> R[Merge with Buckets]
N --> R
Q --> S[Cache Result]
S --> R

R --> T[Sort by Label A-Z]
T --> U[Return Enriched Facets]

G --> U
D --> U

style E fill:#e1f5ff
style I fill:#fff4e1
style L fill:#fff4e1
style O fill:#ffe1e1

Disjunctive Faceting Implementation

graph TD
A[User Applies Filter] --> B[Status=published]
B --> C[Build Facet Queries]

C --> D{For Each Facet}
D --> E[Status Facet]
D --> F[Category Facet]
D --> G[Priority Facet]

Note over E: Exclude its own filter
E --> H[Domain Filter without Status]
H --> I[Apply: Category + Priority]

Note over F: Exclude its own filter
F --> J[Domain Filter without Category]
J --> K[Apply: Status + Priority]

Note over G: Exclude its own filter
G --> L[Domain Filter without Priority]
L --> M[Apply: Status + Category]

I --> N[Execute Solr Queries]
K --> N
M --> N

N --> O[Merge Results]
O --> P[All Options Remain Visible]

style C fill:#e1f5ff
style O fill:#e1ffe1

Facet Type Selection Logic

graph TD
A[Analyze Field] --> B{Field Type?}
B -->|String| C{Cardinality?}
B -->|Numeric| D[Terms + Range]
B -->|Date| E[Date Histogram + Range]
B -->|Boolean| F[Terms Only]

C -->|Low ≤50| G[Terms Facet]
C -->|High >50| H[Not Suitable]

G --> I[categorical]
D --> J[numeric]
E --> K[date]
F --> L[binary]
H --> M[Skip Faceting]

I --> N[Return Facet Config]
J --> N
K --> N
L --> N
M --> O[Exclude from Facets]

style B fill:#e1f5ff
style N fill:#e1ffe1

Caching Strategy

graph TD
A[UUID Resolution Request] --> B[Check Memory Cache]
B --> C{Exists?}
C -->|Yes| D[Return <10ms]
C -->|No| E[Check Distributed Cache]

E --> F{Exists?}
F -->|Yes| G[Return <50ms]
F -->|No| H[Database Query]

H --> I[Batch Load Objects]
I --> J[Extract Names]

J --> K[Store in Distributed Cache]
K --> L[Store in Memory Cache]

L --> M[Return <100ms for 100 UUIDs]

D --> N[Facet Response]
G --> N
M --> N

style B fill:#fff4e1
style E fill:#fff4e1
style H fill:#ffe1e1
style N fill:#e1ffe1

Performance Characteristics

Facet Query Performance:

Without Faceting:    ~50ms  (search only)
With Faceting: ~80ms (search + 5 facets)
With UUID Resolution: ~120ms (search + 5 facets + 100 UUID resolutions)
With Full Caching: ~60ms (search + 5 facets + cached UUIDs)

Caching Impact:

Memory Cache Hit:     <10ms   per UUID resolution
Distributed Cache: <50ms per batch (100 UUIDs)
Database Query: <100ms per batch (100 UUIDs)
No Cache: ~1000ms for 100 individual queries

Code Examples

Building Custom Facet Query

use OCA\OpenRegister\Service\FacetService;

// Get facetable fields
$facetableFields = $facetService->getFacetableFields([
'@self' => ['register' => 5],
'_search' => 'budget'
], 100);

// Build facet configuration
$facets = [
'status' => [
'type' => 'terms',
'field' => 'status_s',
'limit' => 50
],
'created' => [
'type' => 'date_histogram',
'field' => 'self_created',
'interval' => 'month'
]
];

// Execute search with facets
$results = $objectService->findObjects([
'_source' => 'index',
'_facetable' => true,
'_facets' => $facets
]);

Processing Facet Results

// Access facet data
$facets = $results['facets'];

foreach ($facets['@self'] as $fieldName => $facetData) {
echo "Facet: " . $facetData['description'] . "\n";

foreach ($facetData['data'] as $bucket) {
echo " - " . $bucket['label'] . ": " . $bucket['count'] . "\n";
}
}

// Process object field facets
foreach ($facets['object_fields'] as $fieldName => $facetData) {
echo "Object Field: " . $fieldName . "\n";

foreach ($facetData['data'] as $bucket) {
echo " - " . $bucket['value'] . ": " . $bucket['count'] . "\n";
}
}

Testing

# Run faceting tests
vendor/bin/phpunit tests/Service/FacetServiceTest.php

# Test specific scenarios
vendor/bin/phpunit --filter testDisjunctiveFaceting
vendor/bin/phpunit --filter testUUIDResolution
vendor/bin/phpunit --filter testFacetDiscovery

# Integration tests
vendor/bin/phpunit tests/Integration/FacetIntegrationTest.php

Test Coverage:

  • Facet type detection
  • UUID resolution and caching
  • Disjunctive faceting behavior
  • Alphabetical sorting
  • Date histogram buckets
  • Range aggregations
  • Performance benchmarks