Slideshow:
Delete Algorithm for Extensible Hashing
Strength and weakness of the Extensible Hashing method
Strength:
Weakness:
- The delete algorithm is
the same as
the standard
delete algorithm
for hashing
- We do not
consolidate
buckets in
deletion
(Because the ossicilation problem can cause severe performance degradation in Extensible Hashing)
- We do not
consolidate
buckets in
deletion
- Instead of
consolidating:
- Periodically perform rehashing on all search keys in the Extensible Hash Table
- Advantage:
- Always access 1 hash table block to lookup a record
- Problem:
- The size of the
hash table
will double each time
when we extend the table.
- Exponential rate of increase....
Better solution:
- Increase the
hash table size
linearly !!!
- Linear hashing !!! (discussed next)
- The size of the
hash table
will double each time
when we extend the table.