Performance Tuning with SQL Server Dynamic Management Views

Chapter 5: Indexing Strategy and Maintenance
updated. A similar calculation can be used to get the total system reads of an index.
However, we'll ignore any system activity from this point forward as it is almost always
negligible in comparison to user-driven activity.
Over the coming sections, we'll present scripts to:
• find indexes on your system that have never been read or written
• find indexes that have never been read but are being maintained (i.e. updated in
response to modification of the underlying table data)
• get detailed read/write stats on all indexes, looking for those where the maintenance
burden may outweigh their usefulness in boosting query performance.
These indexes are candidates for removal, after thorough investigation. You should
never blindly drop indexes, and you must be certain that an index really isn't used (e.g. by
infrequent, yet critical, monthly or quarterly reporting queries) before dropping it.
Identify indexes that have never been accessed
Listing 5.4 uses sys.indexes and sys.objects to find tables and indexes in the current
database that do not show up in sys.dm_db_index_usage_stats. This means that
these indexes have had no reads or writes since SQL Server was last started, or since the
current database was closed or detached, whichever is shorter.
-- List unused indexes
SELECT OBJECT_NAME(i.[object_id]) AS [Table Name] ,
i.name
FROM sys.indexes AS i
INNER JOIN sys.objects AS o ON i.[object_id] = o.[object_id]
WHERE i.index_id NOT IN ( SELECT ddius.index_id
FROM sys.dm_db_index_usage_stats AS ddius
WHERE ddius.[object_id] = i.[object_id]
AND i.index_id = ddius.index_id
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