Simple select count(id) uses 100% of Azure SQL DTUs

Question

This started off as this question but now seems more appropriately asked specifically since I realised it is a DTU related question.

Basically, running:

Answer 1

select count

should perform clustered index scan if one is available and its up to date. Azure SQL should update statistics automatically, but does not rebuild indexes automatically if they are completely out of date.

if there's a lot of INSERT/UPDATE/DELETE traffic on that table I suggest manually rebuilding the indexes every once in a while.

http://blogs.msdn.com/b/dilkushp/archive/2013/07/28/fragmentation-in-sql-azure.aspx

and SO post for more info

SQL Azure and Indexes