DISTRIBUTED DATABASE MANAGEMENT SYSTEMS A Practical Approach SAEED K. RAHIMI University of St. Thomas FRANK S. HAUG University of St. Thomas A JOHN WILEY & SONS, INC., PUBLICATION DISTRIBUTED DATABASE MANAGEMENT SYSTEMS DISTRIBUTED DATABASE MANAGEMENT SYSTEMS A Practical Approach SAEED K. RAHIMI University of St. Thomas FRANK S. HAUG University of St. Thomas A JOHN WILEY & SONS, INC., PUBLICATION All marks are the properties of their respective owners. IBM® and DB2® are registered trademarks of IBM. JBoss®,RedHat®, and all JBoss-based trademarks are trademarks or registered trademarks of Red Hat, Inc. in the United States and other countries. Linux® is a registered trademark of Linus Torvalds. 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Wiley also publishes its books in a variety of electronic formats. Some content that appears in print, however, may not be available in electronic format. Library of Congress Cataloging-in-Publication Data is available. ISBN 978-0-470-40745-5 Printed in the United States of America. 10987654321 To my mother, Behjat, and my father, Mohammad—though they were not given the opportunity to attend or finish school, they did everything they could to make sure that all of their seven children obtained college degrees. S. K. R. To my mother who taught me to love reading, learning, and books; my father who taught me to love mathematics, science, and computers; and the rest of my family who put up with me while we wrote this book —this would not have been possible without you. F. S. H. CONTENTS Preface xxv 1 Introduction 1 1.1 Database Concepts, 2 1.1.1 Data Models, 2 1.1.2 Database Operations, 2 1.1.3 Database Management, 3 1.1.4 DB Clients, Servers, and Environments, 3 1.2 DBE Architectural Concepts, 4 1.2.1 Services, 4 1.2.2 Components and Subsystems, 5 1.2.3 Sites, 5 1.3 Archetypical DBE Architectures, 6 1.3.1 Required Services, 6 1.3.2 Basic Services, 7 1.3.3 Expected Services, 8 1.3.4 Expected Subsystems, 9 1.3.5 Typical DBMS Services, 10 1.3.6 Summary Level Diagrams, 11 1.4 A New Taxonomy, 13 1.4.1 COS Distribution and Deployment, 13 1.4.2 COS Closedness or Openness, 14 1.4.3 Schema and Data Visibility, 15 1.4.4 Schema and Data Control, 16 1.5 An Example DDBE, 17 1.6 A Reference DDBE Architecture, 18 1.6.1 DDBE Information Architecture, 18 1.6.2 DDBE Software Architecture, 20 vii viii CONTENTS 1.6.2.1 Components of the Application Processor, 21 1.6.2.2 Components of the Data Processor, 23 1.7 Transaction Management in Distributed Systems, 24 1.8 Summary, 31 1.9 Glossary, 32 References, 33 2 Data Distribution Alternatives 35 2.1 Design Alternatives, 38 2.1.1 Localized Data, 38 2.1.2 Distributed Data, 38 2.1.2.1 Nonreplicated, Nonfragmented, 38 2.1.2.2 Fully Replicated, 38 2.1.2.3 Fragmented or Partitioned, 39 2.1.2.4 Partially Replicated, 39 2.1.2.5 Mixed Distribution, 39 2.2 Fragmentation, 39 2.2.1 Vertical Fragmentation, 40 2.2.2 Horizontal Fragmentation, 42 2.2.2.1 Primary Horizontal Fragmentation, 42 2.2.2.2 Derived Horizontal Fragmentation, 44 2.2.3 Hybrid Fragmentation, 47 2.2.4 Vertical Fragmentation Generation Guidelines, 49 2.2.4.1 Grouping, 49 2.2.4.2 Splitting, 49 2.2.5 Vertical Fragmentation Correctness Rules, 62 2.2.6 Horizontal Fragmentation Generation Guidelines, 62 2.2.6.1 Minimality and Completeness of Horizontal Fragmentation, 63 2.2.7 Horizontal Fragmentation Correctness Rules, 66 2.2.8 Replication, 68 2.3 Distribution Transparency, 68 2.3.1 Location Transparency, 68 2.3.2 Fragmentation Transparency, 68 2.3.3 Replication Transparency, 69 2.3.4 Location, Fragmentation, and Replication Transparencies, 69 2.4 Impact of Distribution on User Queries, 69 2.4.1 No GDD—No Transparency, 70 2.4.2 GDD Containing Location Information—Location Transparency, 72 2.4.3 Fragmentation, Location, and Replication Transparencies, 73 2.5 A More Complex Example, 73 2.5.1 Location, Fragmentation, and Replication Transparencies, 75 2.5.2 Location and Replication Transparencies, 76 CONTENTS ix 2.5.3 No Transparencies, 77 2.6 Summary, 78 2.7 Glossary, 78 References, 79 Exercises, 80 3 Database Control 83 3.1 Authentication, 84 3.2 Access Rights, 85 3.3 Semantic Integrity Control, 86 3.3.1 Semantic Integrity Constraints, 88 3.3.1.1 Relational Constraints, 88 3.4 Distributed Semantic Integrity Control, 94 3.4.1 Compile Time Validation, 97 3.4.2 Run Time Validation, 97 3.4.3 Postexecution Time Validation, 97 3.5 Cost of Semantic Integrity Enforcement, 97 3.5.1 Semantic Integrity Enforcement Cost in Distributed System, 98 3.5.1.1 Variables Used, 100 3.5.1.2 Compile Time Validation, 102 3.5.1.3 Run Time Validation, 103 3.5.1.4 Postexecution Time Validation, 104 3.6 Summary, 106 3.7 Glossary, 106 References, 107 Exercises, 107 4 Query Optimization 111 4.1 Sample Database, 112 4.2 Relational Algebra, 112 4.2.1 Subset of Relational Algebra Commands, 113 4.2.1.1 Relational Algebra Basic Operators, 114 4.2.1.2 Relational Algebra Derived Operators, 116 4.3 Computing Relational Algebra Operators, 119 4.3.1 Computing Selection, 120 4.3.1.1 No Index on R, 120 4.3.1.2 B + Tree Index on R, 120 4.3.1.3 Hash Index on R, 122 4.3.2 Computing Join, 123 4.3.2.1 Nested-Loop Joins, 123 4.3.2.2 Sort–Merge Join, 124 4.3.2.3 Hash-Join, 126 4.4 Query Processing in Centralized Systems, 126 4.4.1 Query Parsing and Translation, 127 4.4.2 Query Optimization, 128 4.4.2.1 Cost Estimation, 129 x CONTENTS 4.4.2.2 Plan Generation, 133 4.4.2.3 Dynamic Programming, 135 4.4.2.4 Reducing the Solution Space, 141 4.4.3 Code Generation, 144 4.5 Query Processing in Distributed Systems, 145 4.5.1 Mapping Global Query into Local Queries, 146 4.5.2 Distributed Query Optimization, 150 4.5.2.1 Utilization of Distributed Resources, 151 4.5.2.2 Dynamic Programming in Distributed Systems, 152 4.5.2.3 Query Trading in Distributed Systems, 156 4.5.2.4 Distributed Query Solution Space Reduction, 157 4.5.3 Heterogeneous Database Systems, 170 4.5.3.1 Heterogeneous Database Systems Architecture, 170 4.5.3.2 Optimization in Heterogeneous Databases, 171 4.6 Summary, 172 4.7 Glossary, 173 References, 175 Exercises, 178 5 Controlling Concurrency 183 5.1 Terminology, 183 5.1.1 Database, 183 5.1.1.1 Database Consistency, 184 5.1.2 Transaction, 184 5.1.2.1 Transaction Redefined, 188 5.2 Multitransaction Processing Systems, 189 5.2.1 Schedule, 189 5.2.1.1 Serial Schedule, 189 5.2.1.2 Parallel Schedule, 189 5.2.2 Conflicts, 191 5.2.2.1 Unrepeatable Reads, 191 5.2.2.2 Reading Uncommitted Data, 191 5.2.2.3 Overwriting Uncommitted Data, 192 5.2.3 Equivalence, 192 5.2.4 Serializable Schedules, 193 5.2.4.1 Serializability in a Centralized System, 194 5.2.4.2 Serializability in a Distributed System, 195 5.2.4.3 Conflict Serializable Schedules, 196 5.2.4.4 View Serializable Schedules, 196 5.2.4.5 Recoverable Schedules, 197 5.2.4.6 Cascadeless Schedules, 197 5.2.5 Advanced Transaction Types, 197 5.2.5.1 Sagas, 198 5.2.5.2 ConTracts, 199 CONTENTS xi 5.2.6 Transactions in Distributed System, 199 5.3 Centralized DBE Concurrency Control, 200 5.3.1 Locking-Based Concurrency Control Algorithms, 201 5.3.1.1 One-Phase Locking, 202 5.3.1.2 Two-Phase Locking, 202 5.3.1.3