Refactoring SQL Applications

Chapter 7. Refactoring Flows and Databases

Diseases desperate grown By desperate appliance are relieved, Or not at all.

—William Shakespeare (1564–1616)

Hamlet, IV, 3

SO FAR, I HAVE FOCUSED ON IMPROVING CODE AND MAKING BETTER USE OF THE DBMS FROM A UNITARY standpoint. Not unitary as in “single row,” but unitary as in “single instance of the program.” With the possible exception of some critical batch programs, rarely does a program have exclusive access to a database; most often, multiple instances of the same program or different programs are querying and updating the data concurrently. Ensuring that programs are as efficient and as lean as time, budget, and the weight of history allow is a prerequisite to their working together efficiently. You will never get a great orchestra by assembling bad musicians, and very often one bad musician is enough to ruin the whole orchestra. Bringing together virtuosi is a good start, but it’s not everything. I won’t spoil much by saying that if you replace a complex game of ping-pong between a program and the DBMS with efficient operations, you are in a better position to gear up. Yet, scalability issues are complex, and there is more to orchestrating a harmonious production than improving the performance of processes that run alone, because more points of friction will appear. I briefly mentioned contention and locking in previous chapters, but I didn’t say much about environments where there is intense competition among concurrent users. In these ...