Slide 6 of 21
Notes:
- Function arguments can be base or composite types.
- Functions can be dynamically loaded when required during
query execution.
- Queries cannot be optimized (Black Box)
- Operators: Functions with one or two operands which use
the standard operator notation in the query language.
- Example: In a store, finding departments with floorspace
greater than a specified area,
- retrieve(Dept.dname) where Dept.floorspace AGT polygon
“(0,0), (1,1),(0,2)”
- This query can be optimized. Because floorspace is a base
type- polygon, POSTGRES provides B+-tree index to support
efficient access.
- User Defined Access methods- can be multidimensional sing
R+-trees, grid files, K-D B trees, etc. 13 normal (C)
functions- define how to perform record level operations,
i.e. fetching records, inserting, deleting records.
- POSTQUEL-Packaging collections of POSTQUEL commands.
- Use POSTQUEL functions to define hobbies and related
statistics for each Employee
