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1、复习题31.[DisksandAccessTime]Consideradiskwithasector扇区sizeof512bytes,63sectorspertrack磁道,16,383trackspersurface盘面,8double-sidedplatters柱面(i.e.,16surfaces).Thediskplattersrotateat7,200rpm(revolutionsperminute).Theaverageseektimeis9msec,whereasthetrack-to-trackseek
2、timeis1msec.Supposethatapagesizeof4096bytesischosen.Supposethatafilecontaining1,000,000recordsof256byteseachistobestoredonsuchadisk.Norecordisallowedtospantwopages(usethesenumbersinappropriateplacesinyourcalculation).1)Whatisthecapacityofthedisk?2)Ifthefileisar
3、rangedsequentiallyonthedisk,howmanycylindersareneeded?2.ConstructaB+-treeforthefollowingsetofkeyvalues:(2,3,5,7,11,17,19,23,29,31)Assumethatthetreeisinitiallyemptyandvaluesareaddedinascendingorder.ConstructB+-treesforthecaseswherethenumberofpointersthatwillfiti
4、nonenodeisasfollows:a.Fourb.Sixc.Eight3.ForeachB+-treeofExercise2,showtheformofthetreeaftereachofthefollowingseriesofoperations:a.Insert9.b.Insert10.c.Insert8.d.Delete23.e.Delete19.4.Supposethatweareusingextendablehashingonafilethatcontainsrecordswiththefollowi
5、ngsearch-keyvalues:2,3,5,7,11,17,19,23,29,31Showtheextendablehashstructureforthisfileifthehashfunctionish(x)=xmod8andbucketscanholdthreerecords.5.ShowhowtheextendablehashstructureofPracticeExercise4changesastheresultofeachofthefollowingsteps:a.Delete11.b.Delete
6、31.c.Insert1.d.Insert15.6.ConsidertheinstructorrelationshowninFigure11.1.Figure11.1.Constructabitmapindexontheattributesalary,dividingsalaryvaluesinto4ranges:below50000,50000tobelow60000,60000tobelow70000,and70000andabove.1.设关系r1(A，B，C)，r2(C，D，E)有如下特性：r1有200,00
7、0个元组，r2有45,000个元组，一块中可容纳25个r1元组或30个r2元组；试估算以下每一种策略计算r1
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9、r2所需存取的块数(假设可用于连接操作的内存数量为300个块):1)块嵌套循环连接2)归并连接(假设r1,r2已按连接属性排序)3)混合散列连接(假设分5路进行散列并且没有偏斜)2.设关系r1(A，B，C(fk))，r2(C，D，E(fk))和r3(E，F)，其主码分别为A，C，E。假设r1有35000个元组，r2有25000个元组，r3有10000个元组。试估计r1
10、><
11、r2
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13、r3的元组个数；
