Hugo,
<<If you want to index a computed column, you must persist it.
Are you sure?
I've just added a computed column to one of our big tables (+4 billion rows).
I did not add "PERSISTED" to the alter table statement.
Then I created an index on the column.
Looks fine.
A simple query on the field returns data from the index according to the plan.
But one caveat:
I have a query that currently crashes after 8 hours, when it is using the new index.
We're using SQL Server 2008 sp1 and some cu's.
Best regards,
Henrik Staun Poulsen