Selection with Hashing
Best performance occurs for one queries on hash key field.
Basic strategy:
- compute page address via hash function hash(val)
- fetch that page and look for matching tuple
- possibly fetch additional pages from overflow chain
Best Costone = 1
(find in data page)
Average Costone = 1+Ov/2
(scan half of ovflow chain)
Worst Costone = 1+max(OvLen)
(find in last page of ovflow chain)
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