Early-arriving fact

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In the data warehouse practice of extract, transform, load (ETL), an early fact or early-arriving fact,[1] also known as late-arriving dimension or late-arriving data,[2] 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[edit]

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

References[edit]

  1. ^ "Kimball, Ralph. Design Tip #57: Early Arriving Facts. August, 2004" (PDF). Archived from the original (PDF) on 2007-10-12. Retrieved 2008-04-25.
  2. ^ Early Arriving Facts / Late Arriving Dimensions - LeapFrogBI