title: Early-arriving fact
text: # Early-arriving fact
  
  In the data warehouse practice of extract, transform, load (ETL), an early fact or early-arriving fact, also known as late-arriving dimension or late-arriving data, denotes the detection of a dimensional natural key during fact table source loading, prior to the assignment of a corresponding primary key or surrogate key in the dimension table. Hence, the fact which cites the dimension arrives early, relative to the definition of the dimension value.
  
  ## Handling
  
  Procedurally, an early fact can be treated several ways:
  
  * As an error: On the presumption that the dimensional attribute values should have been collected before fact source loading
  * As a valid fact, pause loading: The collection pauses whilst the missing dimensional attribute value itself is collected
  * As a valid fact, load with dummy keys: A primary key value is generated on the dimension with no attributes (stub / dummy row), the fact completes processing, and the dimension attributes are populated (overwritten) later in the load processing on the new row
  