Inside Symbian SQL. Lead Authors Ivan Litovski with Richard Maynard. Head of Technical Communications, Symbian Foundation Jo Stichbury

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1 Inside Symbian SQL A Mobile Developer s Guide to SQLite Lead Authors Ivan Litovski with Richard Maynard With James Aley, Philip Cheung, James Clarke, Lorraine Martin, Philip Neal, Mike Owens, Martin Platts Reviewed by Erhan Cetintas, Renzo Cherin, Alex Dimitrov, Chris Dudding, Lucian Piros, George Sewell, Andrew Thoelke Head of Technical Communications, Symbian Foundation Jo Stichbury Managing Editor, Symbian Foundation Satu Dahl A John Wiley and Sons, Ltd., Publication

3 Inside Symbian SQL A Mobile Developer s Guide to SQLite

5 Inside Symbian SQL A Mobile Developer s Guide to SQLite Lead Authors Ivan Litovski with Richard Maynard With James Aley, Philip Cheung, James Clarke, Lorraine Martin, Philip Neal, Mike Owens, Martin Platts Reviewed by Erhan Cetintas, Renzo Cherin, Alex Dimitrov, Chris Dudding, Lucian Piros, George Sewell, Andrew Thoelke Head of Technical Communications, Symbian Foundation Jo Stichbury Managing Editor, Symbian Foundation Satu Dahl A John Wiley and Sons, Ltd., Publication

6 This edition first published Symbian Foundation Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Apress hereby grants to John Wiley & Sons, Ltd permission to republish content from Chapters 3 and 4 of The Definitive Guide to SQLite (Apress 2006) by Mike Owens for inclusion in Inside Symbian SQL: A Mobile Developer s Guide to SQLite. Apress retains the non-exclusive right to publish Chapters 3 and 4 of The Definitive Guide to SQLite in a future work. ISBN A catalogue record for this book is available from the British Library. Typeset in 10/12 Optima by Laserwords Private Limited, Chennai, India Printed in Great Britain by TJ International Ltd, Padstow, Cornwall

7 Contents Foreword by Richard Hipp Foreword by Chris Dudding Author Biographies Author s Acknowledgments Symbian Acknowledgments Publisher s Acknowledgements xiii xvii xxi xxv xxvii xxviii 1 Introduction Where Should You Start? Symbian Terminology and Version Numbering The Relational Model and the Structured Query Language (SQL) What Is Symbian SQL? A Well-Oiled Machine Tools and Troubleshooting Further Reading and Resources 6 2 Getting Started Where to Get Symbian SQL 9

8 vi CONTENTS 2.2 Overview of Symbian SQL APIs First Database Example Project Setup Creating a Database Creating a Table Creating an Index Inserting Records Selecting Records Updating a Record Updating Records Using Column Binding and Streaming Deleting a Record Closing a Database Summary 17 3 The Relational Model Background The Three Components SQL and the Relational Model The Structural Component The Information Principle The Sanctity of the Logical Level The Anatomy of the Logical Level Tuples Relations Tables: Relation Variables Views: Virtual Tables The System Catalog The Integrity Component Primary Keys Foreign Keys Constraints Null Values Normalization Normal Forms First Normal Form Functional Dependencies Second Normal Form Third Normal Form The Manipulative Component Relational Algebra and Calculus The Relational Query Language The Advent of SQL 47

9 CONTENTS vii 3.6 The Meaning of Relational Summary 49 4 Everything You Ever Wanted to Know about SQL but Were Afraid to Ask The Relational Model Query Languages Growth of SQL The Example Database Installation Running the Examples Syntax Commands Literals Keywords and Identifiers Comments Creating a Database Creating a Table Altering a Table Querying a Database Relational Operations The Operational Pipeline Filtering Rows Limiting and Ordering Functions and Aggregates Grouping Removing Duplicates Joining Tables Column Names and Aliases Subqueries Compound Queries Conditional Results The Thing Called NULL Set Operations Modifying Data Inserting Records Updating Records Deleting Records Data Integrity Entity Integrity Domain Integrity Storage Classes Manifest Typing 129

10 viii CONTENTS Type Affinity Transactions Transaction Scope Conflict Resolution Transaction Types Database Administration Views Indexes Triggers Attaching Databases Cleaning Databases The System Catalog Viewing Query Plans Summary Database Concepts Database Types Public Databases Private Databases Secure Shared Databases Executing SQL How the Database Processes SQL One-shot Execution Prepared Statements Multi-Client Access Transactions Connections Locking Connections, Transactions and Locking Prepared Statements and Locking Summary Using Symbian SQL The Database Connection Class Connecting and Disconnecting Creating and Deleting Databases Attaching Additional Databases Executing SQL Copying and Deleting a Database File Managing Disk Usage Transaction APIs Retrieving the Security Policy The Prepared Statement Class Preparing and Executing SQL Statements 189

11 CONTENTS ix Retrieving Column Values Parameterized Queries Working with Variable-Length Data Objects Retrieving Data Retrieving Large Amounts of Data Streaming Data The Scalar Query Class Security Policies Summary SQLite Internals on Symbian Why SQLite Is Right for Symbian The SQLite Modules Public Interface Compiler Virtual Machine B-Tree Module Pager OS Interface SQLite Configuration Options Auto-vacuum Page Size Maximum Cache Size Database Encoding SQL Statement Encoding SQLite Optimizations on Symbian OS Sharing the Cache Retaining Page Cache Contents Imposing a Soft Heap Limit Increasing the Maximum Cache Size Avoiding Unnecessary Reads Avoiding Unnecessary Writes Minimizing the Cost of Using Journal Files Mass Storage and Fast Retrieval of Binary Data (BLOBs) Background Database Compaction Summary Performance Tuning Design and Development Considerations Identify Key Use Cases Set Performance Objectives Measure Performance Develop Performance Tests 284

12 x CONTENTS Follow up Test Results An Introduction to Optimization Understand the Operation of the Application Identify Bottlenecks Before Optimizing Avoid Early Optimization Maintain Performance Test Records Carry Out One Optimization at a Time Optimize in the Right Environment Optimizing Applications Application Layer Data Model Indexing SQL Queries Memory Usage System Tuning Symbian SQL Optimization Tips Data Organization Expressions Statements Indexing Using the Optimizer Resource Usage Summary Using Symbian SQL: Three Case Studies Contacts Model Contacts Model on DBMS Aims of Migration Contacts Model on Symbian SQL Possible Future Improvements Case Study Summary Columbo Search Service Why Symbian SQL? Developing with SQLite Case Study Summary Wikipedia Demo Application Downloading the Symbian Wikipedia Demo Application Storing Wikipedia on a Phone Designing the Schema (the Wrong Way) Designing the Schema (the Right Way) Displaying the List of Articles Retrieving the Content of Articles Case Study Summary Summary 367

13 CONTENTS xi Appendix A Troubleshooting 369 A.1 Executing SQL Statements 369 A.2 SQL Language 373 A.3 Memory and Disk Usage 377 A.4 Transactions 378 A.5 Error Handling 380 Appendix B SDB Database Creation Tool 381 B.1 Obtaining and Installing SDB 381 B.2 Using SDB 381 B.3 SDBv1 Configuration Files 383 Appendix C Symbian SQL Error Codes 387 References 389 Index 391

15 Foreword RICHARD HIPP Are you skeptical of the benefits of using the Structured Query Language (SQL) and SQLite in a mobile device? I would be if I were 25 years younger and reading this book for the first time. When I first encountered the SQL language two decades ago, I was deeply suspicious of the whole idea. SQL seemed like a complex solution to a simple problem. Wouldn t it be easier to just read and write directly to various disk files (sometimes called a pile-of-files database) and use a simple key value pair database? In the years that followed that first encounter, I discovered that the SQL programming language does in fact make many programming tasks much, much easier. As applications grow more complex and use richer content, it becomes important to be able to organize that content in a structured way. The pile-of-files and key value approaches quickly become unwieldy. Despite its initial complexity, SQL so greatly simplifies the management of complex data sets that it ends up being a huge net simplification. SQL frees the programmer from the drudgery of low-level I/O interactions and allows the developer to focus on user-facing aspects of the application. A programmer familiar with SQL can often replace hundreds or thousands of lines of low-level I/O code with a single 10-line SQL statement, and in so doing simultaneously scale their productivity and code maintainability. The use of SQL also allows programmers to defer data storage design decisions until late in the design cycle or to make major changes to storage strategies late in a design with minimal impact to code. Furthermore, the transactional model supported by SQL turns out to be an exceedingly powerful abstraction that helps to make applications both more robust and easier to implement.

Inside Symbian SQL. Lead Authors Ivan Litovski with Richard Maynard. Head of Technical Communications, Symbian Foundation Jo Stichbury

Inside Symbian SQL. Lead Authors Ivan Litovski with Richard Maynard. Head of Technical Communications, Symbian Foundation Jo Stichbury Inside Symbian SQL A Mobile Developer s Guide to SQLite Lead Authors Ivan Litovski with Richard Maynard With James Aley, Philip Cheung, James Clarke, Lorraine Martin, Philip Neal, Mike Owens, Martin Platts