http://sqlkingz.blogspot.com

SELECT *
FROM sys.dm_db_missing_index_groups AS g
join sys.dm_db_missing_index_group_stats AS gs ON gs.group_handle = g.index_group_handle
join sys.dm_db_missing_index_details d ON g.index_handle = d.index_handle;

It might be nice to know why the optimizer is not picking up these included columns.

But now if you change Rob’s query to be an inequality query like so:

select productid, orderqty
from sales.salesorderdetail
where carriertrackingnumber > ‘FB88-4B92-82’;

Now the suggested missing index now has the appropriate INCLUDED columns.

Oh, by the way all my testing was on a 32bit machine.

My point is simply that when considering one query in isolation (as we see with the Missing Indexes section of an execution plan now), it should suggest the best index for that query. If the administrator chooses to implement something else, then that’s fine.

I definitely don’t advocate creating every index that the system suggests. I would simply prefer it to suggest the index that would see the most improvement for the query in the plan.

Index maintenance overheads are often described in terms of DML overhead (updates etc). Less widely recognised is the extra space index columns take up, which have daily implications for disk space management, backups, index maintenance & log shipping. These are real problems which should be taken into consideration when deciding to simply throw an extra column onto an index.

Adding extra columns onto indexes should be given similar consideration to throwing extra columns onto tables..

All the suggestions should come with a bit of a warning about the fact that indexes should be considered carefully.

On my machine, the included columns aren’t there in the XML or in the DMV.

@@version gives:
Microsoft SQL Server 2008 (RTM) – 10.0.1600.22 (Intel X86) Jul 9 2008 14:43:34 Copyright (c) 1988-2008 Microsoft Corporation Developer Edition on Windows NT 6.0 (Build 6001: Service Pack 1)

And yes – whilst in the past I’ve found that there were too many included columns listed, I now find this!

Anyway – we’ll have to see what other people find too.

Rob

Can you check the missing index DMV, see if the include columns are listed there? Also, maybe have a look in the exec plan’s XML at the missing index section.

I’m curious as to whether it’s the optimiser not noticing that the include columns would be useful, or management studio just displaying the missing index details wrong.

FWIW, most of the time I find the missing indexes to have too many include columns (up to the point of including the entire table), not too few.

What build of 2008 are you running there?

That’s really interesting. Thanks.

CREATE NONCLUSTERED INDEX []
ON [Sales].[SalesOrderDetail] ([CarrierTrackingNumber])
INCLUDE ([OrderQty],[ProductID])