Question 320
A Date dimension uses many unnecessary text hierarchy columns and hidden calendars. What optimization helps?
Explanation
Correct Answer
Retain required calendar attributes and remove unused auto-generated date structures. Reducing redundant date structures lowers model overhead.
Incorrect Answers
Dimension lookup patterns reduce repeated high-cardinality fact scans. It serves “customer groups directly from a billion-row transaction table”, not “many unnecessary text hierarchy columns and hidden calendars”.
Star-schema relationships clarify filter paths and aggregation grain. The present requirement is “many unnecessary text hierarchy columns and hidden calendars”; “relationship makes a sales report slow and ambiguous” is a distinct situation.
Correct model grain is prerequisite to efficient one-to-many joins. That matters for “keys causing ambiguous cardinality and unexpected filter behavior” rather than the condition “many unnecessary text hierarchy columns and hidden calendars”.