Slideshow:
The use of projection
(π) in query optimization
Using projection
(π) to
remove unnecessary attributes
Example:
- Fact:
- The projection operation π can remove unneccessary attributes from intermediate results
- Common use
the project operation π in
query optimization:
- The
projection operator π
can be added
anywhere in the
relational algebra expression
(= logical query plan/tree),
as long as:
- π will only eliminate attributes that are not used by an operator that is located high up the tree
- The
projection operator π
can be added
anywhere in the
relational algebra expression
(= logical query plan/tree),
as long as:
- Example: