Nested-Loops
Index Physical I/O
•If the join key is an ordinary
sequence-generated ID, the join-key index will naturally cluster
in the order the rows were created.
•In this case, the query need only cache
a few blocks to read thousands of rows from the recent
end of the table – index-block I/O costs are trivial thanks to
self-caching early in the query execution, even if these blocks
are not yet cached.