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 Wysłany: Czw 5:49, 31 Mar 2011 Temat postu: mbt chaussure Tree -based B ^ + relational databas |
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Tree-based B ^ + relational database performance evaluation
Tree to the cost of the (1o) is given, put p; is the probability of sequential access. Then (1 a pt) is collapsing brake cable: visit probability, when the pan tie down system, the average H T. Is: once when the + (1 A p,) cfn. pl,, bl + (1 A p) b pd + (1 ~)} n ((-)+)) fI (c) joint care system overhead costs, including maintenance insert, delete, and modify the firm's marketing spend, when a system maintenance services occurs, the transaction for the insert transaction is defined as the probability p. , The probability for the stripping transactions, defined as the probability for the revision of services is defined as D. , Iol + pd + = 1. So for the system maintenance cost m: C = p. C, + Cd + pC = r. (+2) (+. S + +~(+ ≯ (ts ... 1 + (t ten;) (‰ -) a (H77, t) (+ Jo) (, pj +) t (16) (d) cost of poor efficiency of the foregoing analysis, the effective way to improve response time c 』=,[link widoczny dla zalogowanych], i ~ - Self / 11I cable i brought the number of system maintenance, but also the increase in overhead. NiIg, ~, is to have minimum system maintenance. f under the conditions of sale the fastest response time, here we have to analyze the relationship between the two. Let the index obtained by the establishment of more efficient chip j said. should be equal to the response time of the order of access and use of the response index Time difference: E = c ridge of a first-class ((_72 l09u of Chongqing University, said queries with probability p, p. maintained that the probability, pJ, + p-l cost of using that efficiency is poor,[link widoczny dla zalogowanych], so there: paEP-pC, One analogy I (... and so JJIm a ~ N, 'rI ((1 a )+)|(+ three )(-~-] Og (nd +1), etc.) (Qin + Ⅳ) seven for visual examples and results to express the efficiency cost of the number of poor relations with the index, may wish to give as a sample database and User Services: * number = l · database relationship between the number of attributes m = 30 · between the number of tuples N = 10000: · property {. A {f number of different values., = 1000O; · possession of a stored tuple contains the number of pages = 2 rank = 4 tree into the transaction to the database into a number of tuples r = l: ·, A ... in constraints in the probability P pi = 0.5; · delete the probability p =, insert the probability p = probability p. ==:~, will modify the above assumptions the value of Eq (6.4) 0J0 film of Jane, too: a 2500p a 2.7, o port-T5000p, a 2.7,[link widoczny dla zalogowanych], o. (1 l ship rate between the index price for poor and have Yongning 4: B-tree based on relational database performance evaluated according to equation (1 can draw the difference between the efficiency of generation of stool number and cable} 『curve, as shown. According to the figure of the curve. Xun out, such as F can be concluded: (a) of the query-based applications, using the index can significantly improve system performance. But the index number exceeds a certain limit, the system will not improve performance, but with the increase in the number of index decreased; (b) the probability of query and maintenance operations similar applications. use of the index can be to some extent, improve system performance, but the index is not appropriate to build; (c) to maintain the operation based on the application system,[link widoczny dla zalogowanych], can not be indexed. since the establishment of the system instead of cable 【performance.
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