What might be a reason to create a hidden index?

Creating a hidden index can be particularly useful for testing query performance without affecting the results of queries that depend on visible indexes. When you mark an index as hidden, it remains part of the database but is not used by the query planner for query executions. This allows developers to analyze how queries would perform if they were to use the hidden index versus existing visible indexes.

In scenarios where performance testing is crucial, having a hidden index can provide insights into potential performance improvements or regressions without the risk of impacting live application performance. This temporary measure helps in assessing the efficacy of the index under real-world conditions before making it visible or removing it entirely.

Other options present reasons that do not align with the primary purpose of a hidden index. For instance, while an index can be disabled, creating a hidden index does not permanently disable it for all queries nor does it eliminate it from storage completely; the hidden index still exists and can be made visible again. Additionally, a hidden index does not streamline all query operations since its primary function is to allow testing of the index without impacting regular query execution.