![[assets/ex_indexonlyscan.png|256]] - **Description**: Scans an index without needing to access the table. - **Performance**: Efficient if all needed columns are in the index. - **Factors**: Index size, selectivity, CPU costs. - **Cost**: `index cost + cpu_index_tuple_cost * number of index entries` - ![[assets/ex_index_only_scan.svg|200x200]] - **Workloads**: - [[Workloads/IO]] - [[Workloads/Sub/DataFileRead]] - [[Workloads/LWLock]] - [[Workloads/Sub/BufferContent]] - [[Workloads/Sub/BufferMapping]] - **Operates on**: [[Structures/Index|Index]]