```json { "table_name": "2018", "primary_key": "Country or region", "candidates": [ { "rank": 0, "partition_key": "Country or region", "partition_key_label": "primary_identifier", "partition_key_reasoning": "RPUV=1.00, uniqueness=1.000, 156 unique countries. This is the natural primary identifier for a dimension table containing country-level happiness metrics for a single year (2018). Each country appears exactly once.", "clustering_key": null, "clustering_key_label": null, "clustering_key_reasoning": "Dimension tables typically do not require clustering. The table represents a snapshot of country attributes for 2018 with no internal ordering needed.", "world_line": null, "session_column": null, "confidence": "HIGH", "notes": "This is a dimension table representing World Happiness Report data for 2018. The table name itself indicates the temporal scope (year 2018). Country or region is the unique identifier with perfect uniqueness (RPUV=1.00, 156 unique values for 156 rows). Overall rank is also unique but is a derived attribute based on Score, not a natural identifier. The _ingestion_timestamp, _batch_id, _source_file, and _source_system are metadata columns with RPUV=156 (single value each), making them unsuitable as keys. This table would typically be joined with similar year tables (2015, 2016, 2017, 2019 visible in cross_table_context) for temporal analysis." } ] } ```