Slow distinct query in SQL Server over large dataset

Question

We\'re using SQL Server 2005 to track a fair amount of constantly incoming data (5-15 updates per second). We noticed after it has been in production for a couple months that on

Answer 1

My first thought is statistics. To find last updated:

SELECT
    name AS index_name, 
    STATS_DATE(object_id, index_id) AS statistics_update_date
FROM
    sys.indexes 
WHERE
    object_id = OBJECT_ID('MyTable');

Edit: Stats are updated when indexes are rebuilt, which I see are not maintained

My second thought is that is the index still there? The TOP query should still use an index. I've just tested on one of my tables with 57 million rows and both use the index.