I have a high-demand transactional database that I think is over-indexed. Originally, it didn’t have any indexes at all, so adding some for common processes made a huge difference. However, over time, we’ve created indexes to speed up individual queries, and some of the most popular tables have 10-15 different indexes on them, and in some cases, the indexes are only slightly different from each other, or are the same columns in a different order.
Is there a straightforward way to watch database activity and tell if any indexes are not hit anymore, or what their usage percentage is? I’m concerned that indexes were created to speed up either a single daily/weekly query, or even a query that’s not being run anymore, but the index still has to be kept up to date every time the data changes.
In the case of the high-traffic tables, that’s a dozen times/second, and I want to eliminate indexes that are weighing down data updates while providing only marginal improvement.
Look at the number of user seeks/scans/lookups and last user seek/scan/lookup in sys.dm_db_index_usage_stats. These stats are reset at server start up, so you’d have to check after the server was up and running a relevant load for enought time.