Chapter 2. Waging War

Accessing Databases Efficiently

Il existe un petit nombre de principes fondamentaux de la guerre, dont on ne saurait s'écarter sans danger, et dont l'application au contraire a été presque en tous temps couronnée par le succès.

There exist a small number of fundamental principles of war, which it is dangerous to ignore: indeed, following these principles has almost invariably led to success.

Général Antoine-Henri de Jomini (1779-1869)
Précis de l'Art de la Guerre

Anybody who has ever been involved in the switch from development to production of a critical system knows how much it can feel like the noise and tumult of battle. Very often, a few weeks before D-Day, performance tests will show that the new system is going to fall short of expectations. Experts are brought in, SQL statements are fine-tuned, and database and system administrators are called to contribute to a succession of crisis meetings. Finally, performance vaguely comparable to the previous system is obtained on hardware that is now twice as expensive as the original installation.

Tactics are often used as a substitute for a strategic approach. The latter demands the adoption of a sound overall architecture and design. As in war, the basic principles here are also few, but too often ignored. Architectural mistakes can prove extremely costly, and the SQL programmer must enter the battle fully prepared, knowing where to go and how to get there. In this chapter, we are going to review the key goals that will increase our chances of success in writing programs that access databases efficiently.