Recap on Implementing Selection (cont)
Strategies for implementing selection efficiently
- arrangement of tuples in file (e.g. sorting, hashing)
- auxiliary data structures (e.g. indexes, signatures)
Interested in cost for select, delete, update, and insert
- for
select, simply count number of pages read nr
- for others, use nr and nw to distinguish reads/writes
Typical file structure has
- b main data pages, bOv overflow pages, c tuples per page
- auxiliary files with e.g. oversized values, index entries
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