QueryProc - Outline Introduction Distributed DBMS...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Distributed & Parallel DBMS Page 4. 1 M. Tamer Özsu Outline ± Introduction ± Distributed DBMS Architecture ± Distributed Database Design ² Distributed Query Processing ² Query Processing Methodology ² Distributed Query Optimization ± Distributed Transaction Management ± Data Replication ± Parallel Database Systems ± Data Integration Systems ± Web Search/Querying ± Peer-to-Peer Data Management ± Data Stream Management
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Distributed & Parallel DBMS Page 4. 2 M. Tamer Özsu Query Processing high level user query query processor low level data manipulation commands
Background image of page 2
Distributed & Parallel DBMS Page 4. 3 M. Tamer Özsu Query Processing Components ± Query language that is used z SQL: “intergalactic dataspeak” ± Query execution methodology z The steps that one goes through in executing high-level (declarative) user queries. ± Query optimization z How do we determine the “best” execution plan?
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Distributed & Parallel DBMS Page 4. 4 M. Tamer Özsu SELECT ENAME FROM EMP,ASG WHERE EMP.ENO = ASG.ENO AND DUR > 37 Strategy 1 Π ENAME ( σ DUR>37 EMP.ENO=ASG.ENO (EMP × ASG)) Strategy 2 Π ENAME (EMP ENO ( σ DUR>37 (ASG))) Strategy 2 avoids Cartesian product, so is “better” Selecting Alternatives
Background image of page 4
Distributed & Parallel DBMS Page 4. 5 M. Tamer Özsu What is the Problem? Site 1 Site 2 Site 3 Site 4 Site 5 EMP 1 = σ ENO “E3” (EMP) EMP 2 = σ ENO>“E3” (EMP) ASG 2 = σ ENO>“E3” (ASG) ASG 1 = σ ENO “E3” (ASG) Result Site 5 Site 1 Site 2 Site 3 Site 4 ASG 1 EMP 1 EMP 2 ASG 2 Site 4 Site 3 Site 1 Site 2 Site 5 ' 1 ENO 1 1 ASG EMP EMP = ' ' 2 EMP EMP result = ' 1 ' 2 ENO 2 2 ASG EMP EMP = ' 1 Manager" " RESP 1 ASG σ ASG = = ' 2 Manager" " RESP 2 ASG σ ASG = = ' ' 1 ASG ' 2 ASG ' 1 EMP ' 2 EMP result= (EMP 1 EMP 2 ) ENO σ RESP=“Manager” (EMP1 EMP2)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Distributed & Parallel DBMS Page 4. 6 M. Tamer Özsu ± Assume: z size (EMP) = 400, size (ASG) = 1000 z tuple access cost = 1 unit; tuple transfer cost = 10 units ± Strategy 1 ± produce ASG': (10+10) tuple access cost 20 ² transfer ASG' to the sites of EMP: (10+10) tuple transfer cost 200 ³ produce EMP': (10+10) tuple access cost 24 0 ´ transfer EMP' to result site: (10+10) tuple transfer cost 200 Total cost 460 ± Strategy 2 ± transfer EMP to site 5: 400 tuple transfer cost 4,000 ² transfer ASG to site 5 :1000 tuple transfer cost 10,000 ³ produce ASG':1000 tuple access cost 1,000 ´ join EMP and ASG':400 20 tuple access cost 8,000 Total cost 23,000 Cost of Alternatives
Background image of page 6
Distributed & Parallel DBMS Page 4. 7 M. Tamer Özsu Minimize a cost function I/O cost + CPU cost + communication cost These might have different weights in different distributed environments Wide area networks z communication cost will dominate ± low bandwidth ± low speed ± high protocol overhead z most algorithms ignore all other cost components Local area networks z communication cost not that dominant z total cost function should be considered Can also maximize throughput Query Optimization Objectives
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Distributed & Parallel DBMS Page 4. 8 M. Tamer Özsu ± Assume z Relations of cardinality n z Sequential scan Complexity of Relational Operations
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/23/2009 for the course DBST 663 taught by Professor Tba during the Spring '09 term at MD University College.

Page1 / 41

QueryProc - Outline Introduction Distributed DBMS...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online