Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

Chapter 9: SQL Server Storage and Index Structures
REORGANIZE
Yet another BE CAREFUL! warning on this one. If you disable the clustered index
for your table, it has the effect of disabling the table. The data will remain, but will
be inaccessible by all indexes (since they all depend on the clustered index) until
you rebuild the clustered index.
BINGO!, from the developer perspective. With REORGANIZE, you hit much more of a happy medium in
life. When you reorganize your index, you get a slightly less complete optimization than you get with a
full rebuild, but one that occurs online (users can still utilize the index).
This should, if you’re paying attention, bring about the question, “What exactly do you mean by ‘slightly
less complete’?” Well, REORGANIZE works only on the leaf level of your index — non-leaf levels of the
index go untouched. This means that you’re not quite getting a full optimization, but for the lion’s share
of indexes, that is not where your real cost of fragmentation is (though it can happen, and your mileage
may vary).
Given its much lower impact on users, this is usually the tool you’ll want to use as part of your regular
maintenance plan. We’ll look into this a bit more later when talking fragmentation.
Dropping Indexes
If you’re constantly reanalyzing the situation and adding indexes, don’t forget to drop indexes, too.
Remember the overhead on inserts. It doesn’t make much sense to look at the indexes that you need
and not also think about which indexes you do not need. Always ask yourself: “Can I get rid of any of
these?”
The syntax to drop an index is pretty much the same as that used to drop a table. The only hitch is that
you need to qualify the index name with the table or view it is attached to:
DROP INDEX .
And it’s gone.
Take a Hint from the Query Plan
New with SQL Server 2008 is an indexing hint right within the query-plan information that will tell you
about any indexes that the query optimizer thought would have helped, but that didn’t exist.
Use the Database Engine Tuning Advisor
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It is my hope that you’ll learn enough about indexes not to need the Database Engine Tuning Advisor all
that much, but it still can be quite handy. It works by taking a workload file, which you generate using
the SQL Server Profiler (discussed in Professional SQL Server 2008 Programming), and looking over that
information for what indexes and/or partitions will work best on your system.