Don’t Over-Index

Kenneth Fisher shows the downside cost of non-clustered indexes:

I want to make a couple of final points. I realize 99 indexes is a lot. It’s to emphasize the differences. However they were also fairly small indexes and this is a single table where a normal database might easily have hundreds. So take these results as an example. They aren’t going to match real life but will hopefully show you how all of this can play out.

Indexes are awesome but you want to be smart about adding them. My personal rule of thumb, with no scientific evidence behind it, is 5 indexes or less and I’m pretty easy. 5-10 indexes and you’ll have to convince me. I’m going to be reviewing the existing indexes and see what I can get rid of, or maybe I can combine something. Past 10 indexes and it had best be for a query that’s running a 100+ times a minute or something for the CEO.

Read on for demo code and specific results.

Related Posts

The Costs Of Rebuilding Indexes Online

Tibor Karaszi explains that TANSTAAFL (There A’int No Such Thing As A Free Lunch) applies to online index rebuilds: The time it takes to rebuild the index can be substantially longer for ONLINE. Many of us has other things to do with the database during night-time and/or weekends. Yes, these are the typical window in […]

Read More

The Importance of Cardinality

Bert Wagner shows us why cardinality is important to understand when indexing data: When building indexes for your queries, the order of your index key columns matters.  SQL Server can make the most effective use of an index if the data in that index is stored in the same order as what your query requires for […]

Read More

Categories

October 2016
MTWTFSS
« Sep Nov »
 12
3456789
10111213141516
17181920212223
24252627282930
31