In this section, we study operations that, in one way or another, process their data sequentially. Examples include searching on one or more unindexed attributes, creation of bitmaps based on selection conditions, and scalar aggrega- tion. Grouped aggregation can be achieved by a combina- tion of sorting followed by one scalar aggregation per group. Scan-like operations are also used as components of more complex operations that we will discuss in Section 4 and Section 5. In practice, we need to consider inputs that may be un- aligned, or where the number of elements may not be a multiple of S. Special pieces of code can be used for the rst and last.
