ASA SQL User's Guide
Query Optimization and Execution
Indexes
Types of index
The page size of the database can have a significant effect on the index fan-out. The index fan-out approximately doubles as the page size doubles.
Each index lookup requires one page read for each of the levels of the index plus one page read for the table page, and a single query can require several thousand index lookups. A large fan-out often means that fewer index levels are required, which can improve searches considerably. For this reason, consider using a large page size, such as 4K, to improve index performance. You may also want to consider using a larger page size when you wish to index long string columns using compressed B-tree indexes, but the size limit on smaller page sizes is preventing their creation.