Architecture overview

High-level architecture of the Native Content Relationships plugin.

System components

• Core: Public API (ncr_add_relation, etc.) → Relationship Type Registry → Database (wp_content_relations) + Object Cache
• Integrity: WP-CLI / Cron → Repair logic → Schema & constraint checks → reads/writes DB
• Interfaces: Admin Meta Box, REST API, Elementor Dynamic Tags → all use the Public API

(A Mermaid diagram of this flow is in the repo: docs/ARCHITECTURE.md.)

Key components

1. Registry layer (class-relation-types.php)

• Responsibility: Defines allowed relationship types and their constraints.
• Constraints:
  • max_connections (e.g. One Post to One Author)
  • direction (e.g. bidirectional, from_to, to_from)
  • object_types (e.g. post, user, term)

2. Database layer (class-database.php)

• Table: wp_content_relations
• Indexing:
  • Composite indexes on (from_id, type) and (to_id, type).
  • Covering index on (type, from_id, to_id).
• Schema guard: NCR_SCHEMA_VERSION ensures DB structure updates run only when needed.

3. Integrity engine (class-integrity.php)

• Responsibility: Detects and fixes data inconsistencies.
• Features:
  • Chunked processing: Handles large datasets (1M+ rows) in small batches.
  • Orphan detection: Removes relationships pointing to deleted posts/users.
  • Constraint enforcement: Checks max_connections.

4. Public API (class-api.php)

• Facade: Simple, safe interface (ncr_add_relation, ncr_get_related).
• Validation: Enforces registry rules before writing to DB.
• Caching: Object caching to minimize DB queries.