14
Sep
10

Chapter 32 – Partitioning for manageability (and maybe performance)

The second chapter in a row on partitioning and it’s another excellent chapter.  Dan Guzman – Blog – takes us on an adventure with this chapter in looking at execution plans between partitioning in 2005 and 2008.  In addition he takes the time to spell out what some good use cases are for obtaining additional performance gains from partitioning.

I’m glad that he took the time to do that and it’s one of the most mis-understood elements of partitioning.  Partitioning will not always increase your performance.  As a matter of fact, it could really, really degrade your performance if your partition key, storage and research are well planned. 

In my experience, there is almost always a good partition key which can be found in the data you are looking to partition.  Often it’s a datetime field such as CreatedDate, TransactionDate or InsertedDate etc…  you get the picture.  It’s a date that has a natural order to it over time.  It’s not to say that all records will always land in perfect order but it is to say that more often than not, they will.  Imagine using a column like “ModifiedDate” as your partition key…  every time someone or some process updated a record, it would potentially end up in a different partition; could create havoc.  Or even worse, a column like “birth-date”.  Chances are that very, very few of the Select statements against the employee table contain a where clause with a small range of birthdays…. i.e., I want to see all employees who were born from march – june of 1975.   What good would that do except for the monthly query that H.R. runs to send out Happy Birthday cards?

In closing, I’d recommend that you read this set of blog posts in conjunction with the chapters on partitioning to get started and learn a few things along the way.  https://sqlperspectives.wordpress.com/category/chapter-31/

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