The Row Number List Probe icon indicates that a row number list was used to verify that a row from a previous operation in the query matches the selection criteria used to create the temporary row number list. The use of a row number list probe will allow the optimizer to generate a plan that can process the rows in the table in any manner regardless of any specified selection criteria. As the rows are processed, the ordinal number from the row is used to probe into the row number list to determine if that row matches the selection criteria. This is generally found when an index is used to satisfy the ORDER BY from a query and a separate viable index exists to process the selection criteria.
Also referred to as: Row Number List Probe, Preload