What operation is performed to recalculate the statistics on an index?

Rebuilding an index is the process that effectively recalculates the statistics associated with it. When an index is rebuilt, the database engine creates a new structure for the index and gathers fresh statistics about the data distribution, which helps optimize query performance. Accurate statistics are essential for the query optimizer to create efficient execution plans, as they provide insights into the data distributions and cardinalities within the indexed columns.

Reorganizing an index, on the other hand, does not involve recalculating statistics. Instead, it merely defragments the existing index structure to improve access times without changing its fundamental characteristics or statistics.

Creating an index refers to the initial creation of an index on a table, which includes gathering the initial statistics based on the existing data at that time. Dropping an index involves removing it entirely from the database, thus eliminating the statistics associated with it. Therefore, rebuilding an index is the correct operation to perform when the goal is to ensure that the statistics are up-to-date and accurately reflect the current state of the indexed data.