On a SharePoint 2010 Server installation, I have a list with more than 5000 items. I created an indexed column and a view based on this column which is returning 100 items only, so far less than the throttle limit.
All is working properly, except the columns filters. When I click on any of the columns, the modal dropdown doesn't show any value for filtering. The only thing I can do is sorting.
I made another test by using a DataFormWebPart in multiple list view mode: the dropdown reads "This column type cannot be filtered".
If I try to filter by using the URL parameters (with
&FilterField1=FieldName&FilterValue1=SomeValue), I can see the filters get applied, but if I then click on any column to show the dropdown I get a popup message saying "Cannot show the value of the filter. The field may not be filterable or the number of items returned exceeds the list view threshold".
Does this mean that once a list has exceeded the throttle limit, the automatic column filters that are showed in the XSLT list view webpart cannot be used anymore?
if you want to try and see it for yourself, just create a custom list with two columns, Title and Code (of type Number) and create an index on the Code column. Then, here is an Excel with some test data that you can use to populate the list (just copy from Excel and paste in datasheet view).
EDIT 2 -important-:
In my attempt to strip down the example to make it easier, I actually left out an important piece of the puzzle, which is the throttled list has a lookup column to another list. So, in order to correctly reproduce the issue, you need to add another list (a default custom one with only the title column will do) and add a lookup column to the first list point to the second. It is enough to leave the field empty, it doesn't really have any impact on the behaviour. What I concluded is that if a list has a lookup column, then the automatic filters don't work anymore, even if the index was correctly set and the view is returning less than the throttle limit.