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Magic Sets Optimization Technique for Recursive Datalog. Also a Win on Some Nonrecursive Sql Example of Nonrecursive Use
| Content Provider | Semantic Scholar |
|---|---|
| Abstract | Combines beneets of both top-down backward chaining, recursive tree search and bottom-up forward chaining, naive, seminaive processing of logic, without disadvantages of either. Find the programmers who are making less than the average salary for their department. SELECT e1.name FROM Emps e1 WHERE e1.job = 'programmer' AND e1.sal SELECT AVGe2.sal FROM Emps e2 WHERE e2.dept = e1.dept ; Naive implementation computes the average salary for all departments. Magic-sets" implementation rst determines the departments that have programmers perhaps very few. It can then use an index on Emps.dept to avoid accessing the entire Emps relation. 3. The same parent facts are also useful in the second rule to set up calls" to anc1; Y and anc2; Y. 4. Recursively solve these queries. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://i.stanford.edu/~ullman/cs345notes/slides01-14.pdf |
| Alternate Webpage(s) | http://infolab.stanford.edu/~ullman/cs345notes/slides01-14.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
