Introduction
PostgreSQL is a relational database with a long history. In the late 1970s, the University of California at Berkeley began development of PostgreSQL's ancestor—a relational database known as Ingres. Relational Technologies turned Ingres into a commercial product. Relational Technologies became Ingres Corporation and was later acquired by Computer Associates. Around 1986, Michael Stonebraker from UC Berkeley led a team that added object-oriented features to the core of Ingres; the new version became known as Postgres. Postgres was again commercialized; this time by a company named Illustra, which became part of the Informix Corporation. Andrew Yu and Jolly Chen added SQL support to Postgres in the mid-'90s. Prior versions had used a different, Postgres-specific query language known as Postquel. In 1996, many new features were added, including the MVCC transaction model, more adherence to the SQL92 standard, and many performance improvements. Postgres once again took on a new name: PostgreSQL.
Today, PostgreSQL is developed by an international group of open-source software proponents known as the PostgreSQL Global Development group. PostgreSQL is an open-source product—it is not proprietary in any way. Red Hat has recently commercialized PostgreSQL, creating the Red Hat Database, but PostgreSQL itself will remain free and open source.
PostgreSQL Features
PostgreSQL has benefited well from its long history. Today, PostgreSQL is one of the most advanced database servers available. Here are a few of the features found in a standard PostgreSQL distribution:
Object-relational— In PostgreSQL, every table defines a class. PostgreSQL implements inheritance between tables (or, if you like, between classes). Functions and operators are polymorphic.
Standards compliant— PostgreSQL syntax implements most of the SQL92 standard and many features of SQL99. Where differences in syntax occur, they are most often related to features unique to PostgreSQL.
Open source— An international team of developers maintains PostgreSQL. Team members come and go, but the core members have been enhancing PostgreSQL's performance and feature set since at least 1996. One advantage to PostgreSQL's open-source nature is that talent and knowledge can be recruited as needed. The fact that this team is international ensures that PostgreSQL is a product that can be used productively in any natural language, not just English.
Transaction processing— PostgreSQL protects data and coordinates multiple concurrent users through full transaction processing. The transaction model used by PostgreSQL is based on multi-version concurrency control (MVCC). MVCC provides much better performance than you would find with other products that coordinate multiple users through table-, page-, or row-level locking.
Referential integrity— PostgreSQL implements complete referential integrity by supporting foreign and primary key relationships as well as triggers. Business rules can be expressed within the database rather than relying on an external tool.
Multiple procedural languages— Triggers and other procedures can be written in any of several procedural languages. Server-side code is most commonly written in PL/pgSQL, a procedural language similar to Oracle's PL/SQL. You can also develop server-side code in Tcl, Perl, even bash (the open-source Linux/Unix shell).
Multiple-client APIs— PostgreSQL supports the development of client applications in many languages. This book describes how to interface to PostgreSQL from C, C++, ODBC, Perl, PHP, Tcl/Tk, and Python.
Unique data types— PostgreSQL provides a variety of data types. Besides the usual numeric, string, and data types, you will also find geometric types, a Boolean data type, and data types designed specifically to deal with network addresses.
Extensibility— One of the most important features of PostgreSQL is that it can be extended. If you don't find something that you need, you can usually add it yourself. For example, you can add new data types, new functions and operators, and even new procedural and client languages. There are many contributed packages available on the Internet. For example, Refractions Research, Inc. has developed a set of geographic data types that can be used to efficiently model spatial (GIS) data.
What Versions Does This Book Cover?
The first edition of this book covered versions 7.1 through 7.3. In this edition, we've updated the basics and added coverage for the new features introduced in versions 7.4 and 8.0. Throughout the book, I'll be sure to let you know which features work only in new releases, and, in a few cases, I'll explain features that have been deprecated (that is, features that are obsolete). You can use this book to install, configure, tune, program, and manage PostgreSQL versions 7.1 through 8.0.
Fortunately, the PostgreSQL developers try very hard to maintain forward compatibility—new features tend not to break existing applications. This means that all the features discussed in this book should still be available and substantially similar in later versions of PostgreSQL. I have tried to avoid talking about features that have not been released at the time of writing—where I have mentioned future developments, I will point them out.
Who Is This Book For?
If you are already using PostgreSQL, you should find this book a useful guide to some of the features that you might be less familiar with. The first part of the book provides an introduction to SQL and PostgreSQL for the new user. You'll also find information that shows how to obtain and install PostgreSQL on a Unix/Linux host, as well as on Microsoft Windows.
If you are developing an application that will store data in PostgreSQL, the second part of this book will provide you with a great deal of information relating to PostgreSQL programming. You'll find information on both server-side and client-side programming in a variety of languages.
Every database needs occasional administrative work. The final part of the book should be of help if you are a PostgreSQL administrator, or a developer or user that needs to do occasional administration. You will also find information on how to secure your data against inappropriate use.
Finally, if you are trying to decide which database to use for your current project (or for future projects), this book should provide all the information you need to evaluate whether PostgreSQL will fit your needs.
What Topics Does This Book Cover?
PostgreSQL is a huge product. It's not easy to find the right mix of topics when you are trying to fit everything into a single book. This book is divided into three parts.
The first part, “General PostgreSQL Use,” is an introduction and user's guide for PostgreSQL. Chapter 1, “Introduction to PostgreSQL and SQL,” covers the basics—how to obtain and install PostgreSQL (if you are running Linux, chances are you already have PostgreSQL and it may be installed). The first chapter also provides a gentle introduction to SQL and discusses the sample database we'll be using throughout the book. Chapter 2, “Working with Data in PostgreSQL,” describes the many data types supported by a standard PostgreSQL distribution; you'll learn how to enter values (literals) for each data type, what kind of data you can store with each type, and how those data types are combined into expressions. Chapter 3, “PostgreSQL SQL Syntax and Use,” fills in some of the details we glossed over in the first two chapters. You'll learn how to create new databases, new tables and indexes, and how PostgreSQL keeps your data safe through the use of transactions. Chapter 4, “Performance,” describes the PostgreSQL optimizer. I'll show you how to get information about the decisions made by the optimizer, how to decipher that information, and how to influence those decisions.
Part II, “Programming with PostgreSQL,” is all about PostgreSQL programming. In Chapter 5, “Introduction to PostgreSQL Programming,” we start off by describing the options you have when developing a database application that works with PostgreSQL (and there are a lot of options). Chapter 6, “Extending PostgreSQL,” briefly describes how to extend PostgreSQL by adding new functions, data types, and operators. Chapter 7, “PL/pgSQL,” describes the PL/pgSQL language. PL/pgSQL is a server-based procedural language. Code that you write in PL/pgSQL executes within the PostgreSQL server and has very fast access to data. Each chapter in the remainder of the programming section deals with a client-based API. You can connect to a PostgreSQL server using a number of languages. I show you how to interface to PostgreSQL using C, C++, ecpg, ODBC, JDBC, Perl, PHP, Tcl/Tk, Python, and Microsoft's .NET. Chapters 8 through 18 all follow the same pattern: you develop a series of client applications in a given language. The first client application shows you how to establish a connection to the database (and how that connection is represented by the language in question). The next client adds error checking so that you can intercept and react to unusual conditions. The third client in each chapter demonstrates how to process SQL commands from within the client. The final client wraps everything together and shows you how to build an interactive query processor using the language being discussed. Even if you program in only one or two languages, I would encourage you to study the other chapters in this section. I think you'll find that looking at the same application written in a variety of languages will help you understand the philosophy followed by the PostgreSQL development team, and it's a great way to start learning a new language. Chapter 19, “Other Useful Programming Tools,” introduces you to a few programming tools (and interfaces) that you might find useful: PL/Java and PL/Perl. I'll also show you how to use PostgreSQL inside of bash shell scripts.
The final part of this book (Part III, “PostgreSQL Administration”) deals with administrative issues. The final six chapters of this book show you how to perform the occasional duties required of a PostgreSQL administrator. In the first two chapters, Chapter 20, “Introduction to PostgreSQL Administration,” and Chapter 21, “PostgreSQL Administration,” you'll learn how to start up, shut down, back up, and restore a server. In Chapter 22, “Internationalization and Localization,” you will learn how PostgreSQL supports internationalization and localization. PostgreSQL understands how to store and process a variety of single-byte and multi-byte character sets including Unicode, ASCII, and Japanese, Chinese, Korean, and Taiwan EUC. In Chapter 23, “Security,” I'll show you how to secure your data against unauthorized uses (and unauthorized users). In Chapter 24, “Replicating PostgreSQL with Slony,” you'll learn how to replicate data with PostgreSQL's Slony replication system. Chapter 25, “Contributed Modules,” introduces a few open-source projects that work well with PostgreSQL. I'll show you how to query a PostgreSQL database using XML, how to configure and use TSEARCH2 (a full-text indexing and search system), and how to install and use PgAdmin III, a graphical user interface specifically designed for PostgreSQL.
What's New in the Second Edition?
The first edition of this book hit the shelves in February 2003—at that time, the PostgreSQL developers had just released version 7.3.2. Release 7.4 was unleashed in November 2003. In January 2005, the PostgreSQL developers released version 8.0—a major release full of new features. We timed the second edition of this book to coincide with the release of version 8.0 (the book will appear in bookstores a few months after 8.0 hits the streets). In this edition, we've added coverage for all of the (major) new features in 7.3, 7.4, and 8.0, including
Installing, securing, and managing PostgreSQL on Windows hosts
Tablespaces
Schemas
New quoting mechanisms for string values
New data types (ANYARRAY, ANYELEMENT, VOID)
The standards-conforming INFORMATION_SCHEMA
Nested transactions (SAVEPOINT's)
The new PostgreSQL buffer manager
Auto-vacuum
Prepared-statement execution (the PREPARE/EXECUTE model)
Set-returning functions
Exception handling in PL/pgSQL
libpqxx, the new PostgreSQL interface for C++ clients
New features in ecpg (the embedded SQL processor for C)
New features in the ODBC, JDBC (Java), Perl, Python, PHP, and Tcl/Tk client interfaces
npgsql—the PostgreSQL .NET data provider
Other useful programming tools (PL/Java, pgpash, pgcurl, etc.)
Point-in-time recovery
Replication
Using PostgreSQL with XML
Full-text search
We hope you enjoy this book and find it useful. The PostgreSQL developers have done an incredible job of enhancing what was already a world-class database product. Now dig in.