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Sorted files files compacted ayer dele6ons indexes

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Unformatted text preview: e ignore CPU costs, for simplicity: –  –  –  –  –  B: The number of data pages R: Number of records per page D: (Average) 6me to read or write disk page Measuring number of page I/O’s ignores gains of pre ­fetching a sequence of pages; thus, even I/O cost is only approximated. Average ­case analysis; based on several simplis6c assump6ons.   Good enough to show the overall trends! Comparing File Organiza6ons •  •  •  •  •  Heap files (random order; insert at eof) Sorted files, sorted on <age, sal> Clustered B+ tree file, Alterna6ve (1), search key <age, sal> Heap file with unclustered B + tree index on search key <age, sal> Heap file with unclustered hash index on search key <age, sal> Opera6ons to Compare •  •  •  •  •  Scan: Fetch all records from disk Equality search Range selec6on Insert a record Delete a record Assump6ons in Our Analysis •  Heap Files: –  Equality selec6on on key; exactly one match. •  Sorted Files: –  Files compacted aYer dele6ons. •  Indexes:...
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