Early-arriving fact
# 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
