8 of 8 people found the following review helpful:
4.0 out of 5 stars
Its the context that counts, March 1, 2009
This review is from: Refactoring SQL Applications (Paperback)
Faroult and Hermite focus their attention on relatively classical SQL optimizations. The gist of their advice is that developers running SQL code need to leverage the database engine's optimizer. To do that, they offer relatively common advice: use set operations, avoiding procedural code in your sql code whenever possible; minimize the number of visits to a table; and minimize the number of times your code has to scan a given table. Most of the content of the book is spent offering techniques for achieving these objectives. For developers without a lot of experience writing SQL intensive applications, the authors provide a relatively accessible discussion of these techniques.
Outside of that, the authors include a chapter called `Testing Framework' that addresses one of the key requirements of any refactoring effort: creating and maintaining a library of unit tests that allows us to prove that our code is correct. When writing database code, and particular code whose performance may vary based on the amount of data being processed, unit testing can be a bit of a challenge due to the typical case where developers are developing locally on databases that contain small data sets. In this chapter Faroult and Hermite offer some data generation techniques and some mechanisms for automating the comparison of resulting outputs.
What I like about this book is that unlike books on optimizing the performance of a particular database product, this book tries to elevate the discussion to the level of optimizing the performance of an application that contains a substantial amount of realistic database code. It should enable developers to analyze their code in the context of the business objectives that it is trying to fulfill, rather than the context of the database engine in which it is executing. For that reason alone, I am recommending it to the database developers on my team.
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5 of 5 people found the following review helpful:
5.0 out of 5 stars
For some shops, THE book you need, July 16, 2009
This review is from: Refactoring SQL Applications (Paperback)
I'm at odds with the first two reviewers, but I think it depends on what you're looking for. This book is NOT about classical tuning. Classical tuning is "tune the server", and "tune the query".
The emphasis - in the preface and the excellent Chapter 6 - is that the real gains are usually elsewhere, when you have older code.
I work with a 25 year heritage of fairly well written apps. Many of them have the described situation - a single query that's been broken into two or more parts, with an outer loop and (at least one) inner loop. When server memories were 64K, or 1 Meg, or 4 Meg, and CPU's only came in packages of 1, and disk channels were slow, and networks were slower, this was often the only practical way to get a result.
The interplay changed over the years, but the old code worked. In the past few years, with 64-bit processors, cheap 64-CPU servers, and multi-io disk channels, a wierd thing happened. We found that moving to newer systems and faster hardware made things run SLOWER.
The answer time and again was in those "split loop queries". If we turned them back into one big query - the kind that you couldn't run before, we would see performance improvements of hundreds or thousands of times. In the end, the math proved - on powerful machines, most of the overhead is sending the query, compiling it, and sending it back. If one monster query takes a full second, but every query in the loop takes 1/4 second - if that inner loop runs 1000 times, you lose.
Meantime, that 64-core machine has every CPU working full blast - recompiling the same stupid statement over and over! The problem is, you try to tell this to a developer, they don't beleive you "I didn't change anything in the code".
And that's what this book is about. Changing the code. This book validates what I've been trying to tell my managers and coders; I am grateful to Faoult and L'Hermite for showing I was not making this up myself.
The second reviewer is just reading the wrong book for whatever it is they are trying to do.
This is an essential book for certain people, and is certainly of no interest whatsoever for others. (If you don't own a 1941 Plymouth, the 1941 Plymouth manual isn't much use - otherwise, it's a must).
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1 of 1 people found the following review helpful:
4.0 out of 5 stars
Ask Felgall - Book Review, December 12, 2011
This review is from: Refactoring SQL Applications (Paperback)
Any application that accesses a database will eventually present you with queries that run much slower than is desirable. This book provides you with a guide to how to resolve such problems and get your database accesses to run faster.
The most often suggested solutions are not always the correct ones and this book clearly demonstrates several situations where doing what appears to be an obvious fix (such as adding an index) may actually make things worse.
The author of this book has an in-depth understanding of how databases really work and as a result of the explanations that are provided in this book you can leverage on that to improve the performance of your SQL without needing as complete an understanding as the author has. If anything the book will actually help to give you a greater understanding of how databases work.
Are you going to know where to look when you next have a progr
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