Databasecompression Bothcompressionratio anddecompressioncost matter Smalldecompressionunit (attributeortuple) Oursetting:allowtodecompressasingleattribute 5 EfficientQueryProcessingEfficientQueryProcessing ComparedtouncompressedDB –Whentodecompress –Assumption:nocompressioninqueryprocessing ...
1.BasicStepsinQueryProcessing 1.Parsingandtranslation2.Optimization3.Evaluation DatabaseSystemConcepts-6thEdition 12.3 ©Silberschatz,KorthandSudarshan DatabaseSystemConcepts-6thEdition 12.4 ©Silberschatz,KorthandSudarshan DatabaseSystemConcepts-6thEdition 12.5 ©Silberschatz,KorthandSudarshan Example Select...
Example 1: Left-Deep Plan R1(A,B) TableScan R2(B,C) TableScan R3(C,D) TableScan TNLJ Question: What is the sequence of getNext() calls? Example 1 (contd.) Assume Statistics: –B(R1) = 1000 blocks, T(R1) = 10,000 tuples –B(R2) = 500 blocks, T(R2) = 5000 tuples –...
SQL: Structured Query Language Chapter 5: Part 2. Group-By & Joins. The slides for this text are organized into chapters. This lecture covers Chapter 5. This is one of the most important chapters in any discussion of database systems. Students must acquire a solid grasp of SQL. In partic...
©Silberschatz, Korth and Sudarshan 14.13 Database System Concepts - 5 th Edition, Oct 5, 2006. Equivalence Rules (Cont.) Equivalence Rules (Cont.) 9. The set operations union and intersection are commutative E 1 E 2 = E 2 E
Range(R,Af):R=[l1,h1][l2,h2]…[ld,hd]C,Af(R)=Af({C(x1,x2,…,xd)|(x1,x2,…,xd)R})Example:Range(R=[2,5][2,5],Af=Sum)Range(R,Af)=2+3+3+3+1+5+3+5+1+3+3+4+3+6+1+8=54 2013-5-6 HD-ITR 5 5.1Rangequeryprocessing •Howto...
* <p> * For example, if "op" is "GREATER_THAN" and "v" is 5, * return your estimate of the fraction of elements that are greater than 5. * * @param op Operator * @param v Value * @return Predicted selectivity of this particular operator and value */ public double estimateSelec...
计算机专业英语 第六版 Project Four Information Query and Analysis.ppt,Task one Task One Inquire Information on the Internet The first task is to inquire the necessary information on the Internet. In this task, you must know the necessary information ne
Example: “dogs” and “race” within 4 words match “dogs will begin the race” May also perform stemming and 8、/or not count stop words.,9,Proximity Retrieval with Inverted Index,Use approach similar to phrasal search to find documents in which all keywords are found in a context that...
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