Yes, your understanding is mostly correct. The behavior you’re observing is expected and reflects the distinct purposes of each metadata store:
BigQuery Metadata (Native):
- Location: Directly within BigQuery.
- Purpose: Manages basic descriptions, column names, data types, and table labels—essential for BigQuery’s operation.
Data Catalog (via Entry Groups):
- Location: A separate service within Google Cloud.
- Purpose: Provides rich, business-focused metadata, including technical details (schema, lineage), business context (owners, glossary terms), and governance aspects (tags, policies). Designed as a central repository, Data Catalog facilitates the discovery and understanding of data assets not only within Google Cloud but across multiple platforms, enhancing interoperability and insights.
Dataplex Metadata (via Entities):
- Location: Within the Dataplex lake/zone structure.
- Purpose: Specialized for data lake management, it includes metadata such as data quality metrics, classification labels, and associations with other Dataplex objects. Dataplex is tailored to streamline and govern data integration from diverse sources into cohesive data lakes.
Why Three Independent Sources:
- Decoupling: This separation allows each system to focus on specific functions, providing flexibility and preventing overload in any single system.
- Granularity and Specificity: BigQuery handles basic metadata efficiently, Data Catalog offers expansive, business-oriented metadata capabilities, and Dataplex focuses on operational data lake contexts.
- Use Cases: Use BigQuery metadata for operational functionality, Data Catalog for comprehensive data governance and discovery, and Dataplex for data lake lifecycle management.
Metadata Flow (Or Lack Thereof):
- No Automatic Synchronization: There is no built-in mechanism to synchronize metadata between these platforms, which avoids conflicts and maintains flexibility in operations.
- Manual Synchronization Options: Custom scripts or tools like Cloud Data Fusion can be used to manually synchronize or transform metadata between systems as needed, especially for specialized requirements like compliance or centralized reporting.
Recommendations:
- Choose Your Source of Truth: Decide whether Data Catalog or Dataplex will serve as your primary source for enriched metadata, depending on your specific business needs. This decision can be strategic, with some metadata elements managed predominantly in one service while others are in another, based on their relevance and utility.
- Develop a Governance Strategy: Implement practices to manage and maintain metadata consistently and accurately. Consider using Google Cloud’s IAM for access management and enable auditing to track metadata changes.