查找未使用/只写索引

命令

USE [Musteri];
SELECT OBJECT_SCHEMA_NAME(i.object_id) AS schema_name,
       OBJECT_NAME(i.object_id)        AS table_name,
       i.name                          AS index_name,
       ISNULL(us.user_seeks, 0) + ISNULL(us.user_scans, 0) + ISNULL(us.user_lookups, 0) AS reads,
       ISNULL(us.user_updates, 0)      AS writes,
       ps.used_mb,
       us.last_user_seek, us.last_user_scan,
       N'DROP INDEX ' + QUOTENAME(i.name) + N' ON ' + QUOTENAME(OBJECT_SCHEMA_NAME(i.object_id))
         + N'.' + QUOTENAME(OBJECT_NAME(i.object_id)) + N';' AS drop_stmt_draft
FROM   sys.indexes i
  LEFT JOIN sys.dm_db_index_usage_stats us
         ON us.database_id = DB_ID() AND us.object_id = i.object_id AND us.index_id = i.index_id
  CROSS APPLY (SELECT CAST(SUM(p.used_page_count) * 8 / 1024.0 AS DECIMAL(18,1)) AS used_mb
               FROM sys.dm_db_partition_stats p
               WHERE p.object_id = i.object_id AND p.index_id = i.index_id) ps
WHERE  OBJECTPROPERTY(i.object_id, 'IsUserTable') = 1
  AND  i.type_desc = N'NONCLUSTERED'
  AND  i.is_primary_key = 0 AND i.is_unique_constraint = 0 AND i.is_unique = 0
  AND  ISNULL(us.user_seeks, 0) + ISNULL(us.user_scans, 0) + ISNULL(us.user_lookups, 0) = 0
ORDER BY writes DESC, ps.used_mb DESC;

-- Usage counters since:
SELECT sqlserver_start_time FROM sys.dm_os_sys_info;

作用

列出自重启以来从未被读取（seek/scan/lookup = 0）但仍产生写入成本的非聚集索引及其大小，并生成 DROP INDEX 语句草稿。

适用场景

写密集表上的 INSERT/UPDATE 变慢、要减少存储和维护（重建、CHECKDB）时间，或做索引合并之前。

注意

计数器会在重启、数据库脱机/分离以及（在部分较旧的 2012/2014 版本上）索引重建时重置；只被月末/年末报表使用的索引在短时间窗口内看起来“未使用”。删除前至少观察一个完整业务周期；在 AG 中要分别检查可读辅助副本上的使用情况（计数器按副本统计）。唯一索引即使未被读取也在强制约束；已排除在外。只读查询；安全。