Optimizing Queries with Expensive Predicates

. when optimizing queries without expensive predicates — if no expensive predicates are found while parsing the query, the techniques of this paper need not be invoked. For queries with expensive predicates, . the rest of the paper. 3 Optimal Plans for Queries With Expensive Predicates At first glance, the task of correctly optimizing queries with expensive predicates appears exceedingly complex....

Ngày tải lên: 28/04/2014, 14:09

. (deductive) databases. Within this framework relations and views are modeled, respectively ,with extensional pred- icates (predicates defined by stored facts) and intensional predicates (predicates defined. which at every phase discards views with outside references. A possible research direction is to rank properties with respect to their relevance to individual queries. This will enable the sys...

Ngày tải lên: 16/03/2014, 16:20

. entity graph linking general web queries to entities in a large commercial product catalog. Figure 1a illus- trates eight queries in Q with their observed clicks (solid lines) with products in E 1 . Some. QEC graph: (a) Sample queries in Q, clicks connecting queries with urls in U , and clicks to entities in E; (b) Zoom on edges in C u illustrating clicks observed on urls with weight w u (q, u)....

Ngày tải lên: 30/03/2014, 21:20

. system based on HMM. With a query Q, Miller et al. tried to rank the documents according to the probability that D is relevant (R) with it, which can be written as P(D is R|Q). With Baye’s rule,. model query phrase with local con- texts. So our document score with this basic me- thod can be calculated by multiplying P mGT (q|d) for every q in Q. We can obtain D r with the top 50 scores. r...

Ngày tải lên: 08/03/2014, 01:20

. U.price 4. GENERAL PREDICATES The original KMP algorithm can be used to optimize simple queries, such as that of Example 2.2, in which conditions in the WHERE clause are equality predicates as follows. position coincides with the position immediately after the cursor in the ACM Transactions on Database Systems, Vol. 29, No. 2, June 2004. Expressing and Optimizing Sequence Queries in Database....

Ngày tải lên: 30/03/2014, 22:20

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