The Sorted List Scan icon indicates that the entire temporary sorted list will be scanned and all of the entries contained with the sorted list will be processed. All of the entries contained within the sorted list will be processed, unless the icon label is Sorted List Scan Distinct or Sorted List Scan Distinct, Preload, in which case only one entry from each set of duplicate entries that would be selected within the list will be processed. A sorted list scan can be chosen when the optimizer is considering a plan that requires the data values to be sequenced in a particular order. The use of a sorted list scan will allow the optimizer to generate a plan that can take advantage of any non-join selection while creating the temporary sorted list. An additional benefit of using a sorted list scan is that the data structure of the temporary sorted list will usually cause the table data within the sorted list to remain resident within main memory after creation thus reducing paging on the subsequent scan operations.
Also referred to as: Sorted List Scan, Preload; Sorted List Scan Distinct; Sorted List Distinct, Preload