Algorithms that make use of an existing
index
(e.g., B
+
-tree)
Operators that benefit from an index
The following
algorithm
can be
very
efficient
if an
appropriate
index
is
available
:
σ
Attr = constant
(R)
-- and there is an
index
on the
select attribute(s)
σ
Attr ≥ constant
(R)
-- and there is an
index
on the
select attribute(s)
R
⋈
S
-- and there is an
index
on the
join attribute(s)