如何在sql数据库中监视和查找未使用的索引

时间：2009-09-21 19:53:03

标签： sql-server indexing maintenance

我想监视sql数据库的索引使用情况，以便找到未使用的索引，然后删除它们。如何最有效地监控索引使用情况？哪些脚本可能有用？

（我知道this question about identifying unused objects，但这只适用于sql server的当前运行。我想监视一段时间内的索引使用情况......）

5 个答案:

答案 0 :(得分：7)

目前（从SQL Server 2005 - 2008开始），SQL索引统计信息仅保留在内存中，因此如果您希望在重新启动和数据库分离时保持这种状态，则必须自己完成一些工作。

我通常做的是创建一个每天运行的作业，并将sys.dm_db_index_usage_stats表中的信息快照放入我为相关数据库创建的自定义表中。

在将来支持持久索引使用统计数据的SQL的未来版本之前，这似乎工作得很好。

答案 1 :(得分：7)

这是一个有趣的问题。过去一周我一直在研究同样的问题。有一个名为dm_db_index_usage_stats的系统表，其中包含索引的使用情况统计信息。

使用情况统计表中从不出现的索引

但是，许多索引根本不会出现在此表中。 David Andres发布的查询列出了此案例的所有索引。我已经更新了一点点忽略了主键，这些主键可能不应该删除，即使它们从未被使用过。我还加入了dm_db_index_physical_stats表以获取其他信息，包括页面计数，总索引大小和碎片百分比。一个有趣的注意事项是，此查询返回的索引似乎没有显示在索引使用情况统计信息的SQL报告中。

DECLARE @dbid INT
SELECT @dbid = DB_ID(DB_NAME())

SELECT  Databases.Name AS [Database],
        Objects.NAME AS [Table],
        Indexes.NAME AS [Index],
        Indexes.INDEX_ID,
        PhysicalStats.page_count as [Page Count],
        CONVERT(decimal(18,2), PhysicalStats.page_count * 8 / 1024.0) AS [Total Index Size (MB)],
        CONVERT(decimal(18,2), PhysicalStats.avg_fragmentation_in_percent) AS [Fragmentation (%)]
FROM SYS.INDEXES Indexes
    INNER JOIN SYS.OBJECTS Objects ON Indexes.OBJECT_ID = Objects.OBJECT_ID
    LEFT JOIN sys.dm_db_index_physical_stats(@dbid, null, null, null, null) PhysicalStats
        on PhysicalStats.object_id = Indexes.object_id and PhysicalStats.index_id = indexes.index_id
    INNER JOIN sys.databases Databases
        ON Databases.database_id = PhysicalStats.database_id
WHERE OBJECTPROPERTY(Objects.OBJECT_ID,'IsUserTable') = 1
    AND Indexes.type = 2    -- Nonclustered indexes
    AND   Indexes.INDEX_ID NOT IN (
            SELECT UsageStats.INDEX_ID
            FROM SYS.DM_DB_INDEX_USAGE_STATS UsageStats
            WHERE UsageStats.OBJECT_ID = Indexes.OBJECT_ID
                AND   Indexes.INDEX_ID = UsageStats.INDEX_ID
                AND   DATABASE_ID = @dbid)
ORDER BY PhysicalStats.page_count DESC,
         Objects.NAME,
         Indexes.INDEX_ID,
         Indexes.NAME ASC

在使用情况统计表中出现但从未使用的索引

dm_db_index_usage_stats表中确实存在其他索引，但这些索引从未用于用户搜索，扫描或查找。此查询将标识属于此类别的索引。顺便说一句，与从其他查询返回的索引不同，此查询中返回的索引可以通过索引使用情况统计信息在SQL报告上进行验证。

我添加了一个最小页数，它允许我最初关注并删除占用大量存储空间的未使用索引。

DECLARE @MinimumPageCount int
SET @MinimumPageCount = 500

SELECT  Databases.name AS [Database], 
        Indexes.name AS [Index],
        Objects.Name AS [Table],                    
        PhysicalStats.page_count as [Page Count],
        CONVERT(decimal(18,2), PhysicalStats.page_count * 8 / 1024.0) AS [Total Index Size (MB)],
        CONVERT(decimal(18,2), PhysicalStats.avg_fragmentation_in_percent) AS [Fragmentation (%)],
        ParititionStats.row_count AS [Row Count],
        CONVERT(decimal(18,2), (PhysicalStats.page_count * 8.0 * 1024) / ParititionStats.row_count) AS [Index Size/Row (Bytes)]
FROM sys.dm_db_index_usage_stats UsageStats
    INNER JOIN sys.indexes Indexes
        ON Indexes.index_id = UsageStats.index_id
            AND Indexes.object_id = UsageStats.object_id
    INNER JOIN sys.objects Objects
        ON Objects.object_id = UsageStats.object_id
    INNER JOIN SYS.databases Databases
        ON Databases.database_id = UsageStats.database_id       
    INNER JOIN sys.dm_db_index_physical_stats (DB_ID(), NULL, NULL, NULL, NULL) AS PhysicalStats
        ON PhysicalStats.index_id = UsageStats.Index_id 
            and PhysicalStats.object_id = UsageStats.object_id
    INNER JOIN SYS.dm_db_partition_stats ParititionStats
        ON ParititionStats.index_id = UsageStats.index_id
            and ParititionStats.object_id = UsageStats.object_id        
WHERE UsageStats.user_scans = 0
    AND UsageStats.user_seeks = 0
    AND UsageStats.user_lookups = 0
    AND PhysicalStats.page_count > @MinimumPageCount    -- ignore indexes with less than 500 pages of memory
    AND Indexes.type_desc != 'CLUSTERED'                -- Exclude primary keys, which should not be removed    
ORDER BY [Page Count] DESC

我希望这会有所帮助。

最后的想法

当然，一旦索引被识别为候选人被删除，仍应仔细考虑，以确保这样做是一个很好的决定。

有关详细信息，请参阅Identifying Unused Indexes in a SQL Server Database

答案 2 :(得分：3)

将这只小狗从http://blog.sqlauthority.com/2008/02/11/sql-server-2005-find-unused-indexes-of-current-database/上拉下来。请注意，这适用于2005年及以上。关键是JOIN到SYS.DM_DB_INDEX_USAGE_STATS系统表。

USE AdventureWorks
GO
DECLARE @dbid INT
SELECT @dbid = DB_ID(DB_NAME())
SELECT OBJECTNAME = OBJECT_NAME(I.OBJECT_ID),
                    INDEXNAME = I.NAME,
                    I.INDEX_ID
FROM SYS.INDEXES I
JOIN SYS.OBJECTS O ON I.OBJECT_ID = O.OBJECT_ID
WHERE OBJECTPROPERTY(O.OBJECT_ID,'IsUserTable') = 1
AND   I.INDEX_ID NOT IN (

SELECT S.INDEX_ID
FROM SYS.DM_DB_INDEX_USAGE_STATS S
WHERE S.OBJECT_ID = I.OBJECT_ID
AND   I.INDEX_ID = S.INDEX_ID
AND   DATABASE_ID = @dbid)
ORDER BY OBJECTNAME,
         I.INDEX_ID,
         INDEXNAME ASC
GO

答案 3 :(得分：3)

我在这里调整了John Pasquet的查询：Identifying Unused Indexes in a SQL Server Database返回使用10次或更少次数的索引，联合使用统计表中没有的结果，排除堆索引和唯一约束或主键索引，最后排除零页面的索引。

小心这个查询的结果 - 最好在生产中使用，其中索引实际上以您期望的方式使用。如果使用重建或删除/重新创建的索引或最近的数据库备份查询数据库，则可能会出现误报（通常会使用的索引，但不是因为特殊情况）。在测试或开发环境中使用以决定是否删除索引是不安全的。正如纳尔尼亚所说，这个查询只是为了仔细考虑确定了删除的候选人。

USE [DatabaseName]

DECLARE @MinimumPageCount int
SET @MinimumPageCount = 500

DECLARE @dbid INT
SELECT @dbid = DB_ID(DB_NAME())

-- GET UNUSED INDEXES THAT APPEAR IN THE INDEX USAGE STATS TABLE

SELECT  
    Databases.name AS [Database]
    ,object_name(Indexes.object_id) AS [Table]
    ,Indexes.name AS [Index]
    ,PhysicalStats.page_count as [Page Count]
    ,CONVERT(decimal(18,2), PhysicalStats.page_count * 8 / 1024.0) AS [Total Index Size (MB)]
    ,CONVERT(decimal(18,2), PhysicalStats.avg_fragmentation_in_percent) AS [Fragmentation (%)]
    ,ParititionStats.row_count AS [Row Count]
    ,CONVERT(decimal(18,2), (PhysicalStats.page_count * 8.0 * 1024) / ParititionStats.row_count) AS [Index Size Per Row (Bytes)]
    ,1 AS [Appears In Usage Stats Table]

FROM sys.dm_db_index_usage_stats UsageStats

INNER JOIN sys.indexes Indexes
    ON Indexes.index_id = UsageStats.index_id AND Indexes.object_id = UsageStats.object_id

INNER JOIN SYS.databases Databases
    ON Databases.database_id = UsageStats.database_id

INNER JOIN sys.dm_db_index_physical_stats (DB_ID(),NULL,NULL,NULL,NULL) AS PhysicalStats
    ON PhysicalStats.index_id = UsageStats.Index_id AND PhysicalStats.object_id = UsageStats.object_id

INNER JOIN SYS.dm_db_partition_stats ParititionStats
    ON ParititionStats.index_id = UsageStats.index_id AND ParititionStats.object_id = UsageStats.object_id

WHERE 
    UsageStats.user_scans <= 10
    AND UsageStats.user_seeks <= 10
    AND UsageStats.user_lookups <= 10

    -- exclude heap indexes
    AND Indexes.name IS NOT NULL

    -- ignore indexes with less than a certain number of pages of memory
    AND PhysicalStats.page_count > @MinimumPageCount

    -- Exclude primary keys, which should not be removed
    AND Indexes.is_primary_key = 0

    -- ignore unique constraints - those shouldn't be removed 
    AND Indexes.is_unique_constraint = 0 
    AND Indexes.is_unique = 0

UNION ALL 
(
    -- GET UNUSED INDEXES THAT DO **NOT** APPEAR IN THE INDEX USAGE STATS TABLE

    SELECT  
        Databases.Name AS [Database]
        ,Objects.NAME AS [Table]
        ,Indexes.NAME AS [Index]
        ,PhysicalStats.page_count as [Page Count]
        ,CONVERT(decimal(18,2), PhysicalStats.page_count * 8 / 1024.0) AS [Total Index Size (MB)]
        ,CONVERT(decimal(18,2), PhysicalStats.avg_fragmentation_in_percent) AS [Fragmentation (%)]
        ,-1 AS [Row Count]
        ,-1 AS [Index Size Per Row (Bytes)]
        ,0 AS [Appears In Usage Stats Table]

    FROM SYS.INDEXES Indexes

    INNER JOIN SYS.OBJECTS Objects 
        ON Indexes.OBJECT_ID = Objects.OBJECT_ID

    LEFT JOIN sys.dm_db_index_physical_stats(@dbid, null, null, null, null) PhysicalStats
        ON PhysicalStats.object_id = Indexes.object_id AND PhysicalStats.index_id = indexes.index_id

    INNER JOIN sys.databases Databases
        ON Databases.database_id = PhysicalStats.database_id

    WHERE 
        Objects.type = 'U' -- Is User Table

        -- exclude heap indexes
        AND Indexes.name IS NOT NULL

        -- exclude empty tables
        AND PhysicalStats.page_count <> 0

        -- Exclude primary keys, which should not be removed
        AND Indexes.is_primary_key = 0

        -- ignore unique constraints - those shouldn't be removed 
        AND Indexes.is_unique_constraint = 0 
        AND Indexes.is_unique = 0

        AND Indexes.INDEX_ID NOT IN 
        (
            SELECT UsageStats.INDEX_ID
            FROM SYS.DM_DB_INDEX_USAGE_STATS UsageStats
            WHERE 
                UsageStats.OBJECT_ID = Indexes.OBJECT_ID
                AND Indexes.INDEX_ID = UsageStats.INDEX_ID
                AND DATABASE_ID = @dbid
        )
)

ORDER BY [Table] ASC, [Total Index Size (MB)] DESC

答案 4 :(得分：0)

你应该看看布伦特·奥扎尔sp_BlitzIndex。此存储过程列出了其他未使用的索引。它列出了报告中的疾病。对于每个条目，都会给出一个URL，说明要查找的内容以及如何处理该问题。

相关问题
最新问题