Overview

It is a bad plan that admits of no modification.

Publilius Syrus (~100 B.C.), Maxims

Make a new plan Stan and get yourself free.

Paul Simon

Throughout this book we ve presented the major attributes of physical database design, and how they are used and why. How can you determine if a specific database design attribute is really helping or hurting your database? Or even more fundamentally, how can you determine if a design feature is being used by the database? There s a brute-force method of course: Run experiments with your application workload to evaluate the contributions of every single physical design change to determine the impact. This kind of brute-force strategy is probably inefficient since it means actually creating and testing each design possibility with a real database packed with a lot of data. There s another way to evaluate the benefit of design choices, and interestingly it s the same method that the database itself uses; namely, to examine the impact of design choices on the query execution plans of your workload. This technique is in fact the dominant technique used by database administrators (DBAs) and database designers for every major database product, and as a result every major database product provides tooling to allow users to examine the query execution plans chosen by the database for each query. By viewing the query execution plan one can observe whether the database itself thinks that design choices, such as materialized views and indexes, are likely to be ...