- Hash table on top of sequential file.
- Index has a (key, record id) entry for each record.
Operations
- Scan: Scan the sequential file, the index doesn't help! Index
scan would generate a lot of random accesses.
- Equality search: Search the index, then follow the record
id. 2 random accesses.
- Range search: Again, index doesn't help, scan the sequential
file.
- Insert: Append to the sequential file, update hash index.
- Update: Find the record using the hash table, update the record.
- Delete: Find the record using the hash table, delete the record, remove the hash entry.