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# 1. INTRODUCTION

This document is the user manual for the POSTGRES95 database management system developed at the University of California at Berkeley. POSTGRES95 is based on POSTGRES release 4.2. The POSTGRES project, led by Professor Michael Stonebraker, has been sponsored by the Defense Advanced Research Projects Agency (DARPA), the Army Research Office (ARO), the National Science Foundation (NSF), and ESL, Inc.

## 1.1. What is POSTGRES?

Traditional relational database management systems (DBMSs) support a data model consisting of a collection of named relations, containing attributes of a specific type. In current commercial systems, possible types include floating point numbers, integers, character strings, money, and dates. It is commonly recognized that this model is inadequate for future data processing applications. The relational model successfully replaced previous models in part because of its "Spartan simplicity". However, as mentioned, this simplicity often makes the implementation of certain applications very difficult to implement. POSTGRES offers substantial additional power by incorporating the following four additional basic constructs in such a way that users can easily extend the system:

             classes
             inheritance
             types
             functions

In addition, POSTGRES supports a powerful production rule system.

## 1.2. A Short History of the POSTGRES Project

Implementation of the POSTGRES DBMS began in 1986. The initial concepts for the system were presented in [STON86] and the definition of the initial data model appeared in [ROWE87]. The design of the rule system at that time was described in [STON87a]. The rationale and architecture of the storage manager were detailed in [STON87b]. POSTGRES has undergone several major releases since then. The first "demoware" system became operational in 1987 and was shown at the 1988 ACM-SIGMOD Conference. We released Version 1, described in [STON90a], to a few external users in June 1989. In response to a critique of the first rule system [STON89], the rule system was redesigned [STON90b] and Version 2 was released in June 1990 with the new rule system. Version 3 appeared in 1991 and added support for multiple storage managers, an improved query executor, and a rewritten rewrite rule system. For the most part, releases since then have focused on portability and reliability. POSTGRES has been used to implement many different research and production applications. These include: a financial data analysis system, a jet engine performance monitoring package, an asteroid tracking database, a medical information database, and several geographic information systems. POSTGRES has also been used as an educational tool at several universities. Finally, Illustra Information Technologies picked up the code and commercialized it. POSTGRES became the primary data manager for the Sequoia 2000 scientific computing project in late 1992. Furthermore, the size of the external user community nearly doubled during 1993. It became increasingly obvious that maintenance of the prototype code and support was taking up large amounts of time that should have been devoted to database research. In an effort to reduce this support burden, the project officially ended with Version 4.2.

## 1.3. What is POSTGRES95?

POSTGRES95 is a derivative of the last official release of POSTGRES (version 4.2). The code is now completely ANSI C and the code size has been trimmed by 25%. There are a lot of internal changes that improve performance and code maintainability. POSTGRES95 runs about 30-50% faster on the Wisconsin Benchmark compared to v4.2. Apart from bug fixes, these are the major enhancements:

- The query language POSTQUEL has been replaced with SQL (implemented in the server). We do not support subqueries (which can be imitated with user defined SQL functions) at the moment. Aggregates have been re-implemented. We also added support for GROUP BY. The libpq interface is still available for C programs.
- In addition to the monitor program, we provide a new program (psql) which supports GNU readline.
- We added a new front-end library, libpgtcl, that supports Tcl-based clients. A sample shell, pgtclsh, provides new Tcl commands to interface tcl programs with the POSTGRES95 backend.
- The large object interface has been overhauled. We kept Inversion large objects as the only mechanism for storing large objects. (This is not to be confused with the Inversion file system which has been removed.)
- The instance-level rule system has been removed.
- Rules are still available as rewrite rules.
- A short tutorial introducing regular SQL features as well as those of ours is distributed with the source code.
- GNU make (instead of BSD make) is used for the build. Also, POSTGRES95 can be compiled with an unpatched gcc (data alignment of doubles has been fixed).

## 1.4. About This Release

POSTGRES95 is available free of charge. This manual describes version 1.0 of POSTGRES95. The authors have compiled and tested POSTGRES95 on the following platforms:

Architecture | Processor | Operating System
--- | --- | ---
DECstation 3000 | Alpha AXP | OSF/1 2.1, 3.0, 3.2
DECstation 5000 | MIPS | ULTRIX 4.4
Sun4 | SPARC | SunOS 4.1.3, 4.1.3_U1; Solaris 2.4
H-P 9000/700 and 800 | PA-RISC | HP-UX 9.00, 9.01, 9.03
Intel | X86 | Linux 1.2.8, ELF

## 1.5. Outline of This Manual

From now on, We will use POSTGRES to mean POSTGRES95. The first part of this manual goes over some basic sys- tem concepts and procedures for starting the POSTGRES system. We then turn to a tutorial overview of the POSTGRES data model and SQL query language, introducing a few of its advanced features. Next, we explain the POSTGRES approach to extensibility and describe how users can extend POSTGRES by adding user-defined types, operators, aggregates, and both query language and pro- gramming language functions. After an extremely brief overview of the POSTGRES rule system, the manual concludes with a detailed appendix that discusses some of the more involved and operating system-specific procedures involved in extending the system.

UNIX is a trademark of X/Open, Ltd. Sun4, SPARC, SunOS and Solaris are trademarks of Sun Microsystems, Inc. DEC, DECstation, Alpha AXP and ULTRIX are trademarks of Digital Equipment Corp. PA-RISC and HP-UX are trademarks of Hewlett-Packard Co. OSF/1 is a trademark of the Open Software Foundation.

We assume proficiency with UNIX and C programming.

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