有关索引的DMV（转）

转自：http://www.cnblogs.com/CareySon/archive/2012/05/17/2505981.html

1.查看那些被大量更新，却很少被使用的索引

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

SELECT

    DB_NAME() AS DatabaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , s.user_updates

    , s.system_seeks + s.system_scans + s.system_lookups

                          AS [System usage]

INTO #TempUnusedIndexes

FROM   sys.dm_db_index_usage_stats s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE 1=2

EXEC sp_MSForEachDB 'USE [?];

INSERT INTO #TempUnusedIndexes

SELECT TOP 20

    DB_NAME() AS DatabaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , s.user_updates

    , s.system_seeks + s.system_scans + s.system_lookups

                                         AS [System usage]

FROM   sys.dm_db_index_usage_stats s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE s.database_id = DB_ID()

AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0

AND s.user_seeks = 0

    AND s.user_scans = 0

    AND s.user_lookups = 0

AND i.name IS NOT NULL

ORDER BY s.user_updates DESC'

SELECT TOP 20 * FROM #TempUnusedIndexes ORDER BY [user_updates] DESC

DROP TABLE #TempUnusedIndexes

结果如图:

这类索引应该被Drop掉

最高维护代价的索引

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

SELECT

    DB_NAME() AS DatabaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , (s.user_updates ) AS [update usage]

    , (s.user_seeks + s.user_scans + s.user_lookups) AS [Retrieval usage]

    , (s.user_updates) -

      (s.user_seeks + s.user_scans + s.user_lookups) AS [Maintenance cost]

    , s.system_seeks + s.system_scans + s.system_lookups AS [System usage]

    , s.last_user_seek

    , s.last_user_scan

    , s.last_user_lookup

INTO #TempMaintenanceCost

FROM   sys.dm_db_index_usage_stats s

INNER JOIN sys.indexes i ON  s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE 1=2

EXEC sp_MSForEachDB 'USE [?];

INSERT INTO #TempMaintenanceCost

SELECT TOP 20

    DB_NAME() AS DatabaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , (s.user_updates ) AS [update usage]

    , (s.user_seeks + s.user_scans + s.user_lookups)

                    AS [Retrieval usage]

    , (s.user_updates) -

(s.user_seeks + user_scans +

                         s.user_lookups) AS [Maintenance cost]

    , s.system_seeks + s.system_scans + s.system_lookups AS [System usage]

    , s.last_user_seek

    , s.last_user_scan

    , s.last_user_lookup

FROM   sys.dm_db_index_usage_stats s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE s.database_id = DB_ID()

    AND i.name IS NOT NULL

    AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0

    AND (s.user_seeks + s.user_scans + s.user_lookups) > 0

ORDER BY [Maintenance cost] DESC'

SELECT top 20 * FROM #TempMaintenanceCost ORDER BY [Maintenance cost] DESC

DROP TABLE #TempMaintenanceCost

结果如图:

Maintenance cost高的应该被Drop掉

使用频繁的索引

--使用频繁的索引

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

SELECT

    DB_NAME() AS DatabaseName

        , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , (s.user_seeks + s.user_scans + s.user_lookups) AS [Usage]

    , s.user_updates

    , i.fill_factor

INTO #TempUsage

FROM sys.dm_db_index_usage_stats s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE 1=2

EXEC sp_MSForEachDB 'USE [?];

INSERT INTO #TempUsage

SELECT TOP 20

    DB_NAME() AS DatabaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , (s.user_seeks + s.user_scans + s.user_lookups) AS [Usage]

    , s.user_updates

    , i.fill_factor

FROM   sys.dm_db_index_usage_stats s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

            AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE s.database_id = DB_ID()

    AND i.name IS NOT NULL

    AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0

ORDER BY [Usage] DESC'

SELECT TOP 20 * FROM #TempUsage ORDER BY [Usage] DESC

DROP TABLE #TempUsage

结果如图

这类索引需要格外注意，不要在优化的时候干掉

碎片最多的索引

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

SELECT

    DB_NAME() AS DatbaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , ROUND(s.avg_fragmentation_in_percent,2) AS [Fragmentation %]

INTO #TempFragmentation

FROM sys.dm_db_index_physical_stats(db_id(),null, null, null, null) s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE 1=2

EXEC sp_MSForEachDB 'USE [?];

INSERT INTO #TempFragmentation

SELECT TOP 20

    DB_NAME() AS DatbaseName

    , SCHEMA_NAME(o.Schema_ID) AS SchemaName

    , OBJECT_NAME(s.[object_id]) AS TableName

    , i.name AS IndexName

    , ROUND(s.avg_fragmentation_in_percent,2) AS [Fragmentation %]

FROM sys.dm_db_index_physical_stats(db_id(),null, null, null, null) s

INNER JOIN sys.indexes i ON s.[object_id] = i.[object_id]

    AND s.index_id = i.index_id

INNER JOIN sys.objects o ON i.object_id = O.object_id

WHERE s.database_id = DB_ID()

  AND i.name IS NOT NULL

  AND OBJECTPROPERTY(s.[object_id], ''IsMsShipped'') = 0

ORDER BY [Fragmentation %] DESC'

SELECT top 20 * FROM #TempFragmentation ORDER BY [Fragmentation %] DESC

DROP TABLE #TempFragmentation

结果如下:

这类索引需要Rebuild,否则会严重拖累数据库性能

自上次SQL Server重启后，找出完全没有使用的索引

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

SELECT

    DB_NAME() AS DatbaseName

    , SCHEMA_NAME(O.Schema_ID) AS SchemaName

    , OBJECT_NAME(I.object_id) AS TableName

    , I.name AS IndexName

INTO #TempNeverUsedIndexes

FROM sys.indexes I INNER JOIN sys.objects O ON I.object_id = O.object_id

WHERE 1=2

EXEC sp_MSForEachDB 'USE [?];

INSERT INTO #TempNeverUsedIndexes

SELECT

    DB_NAME() AS DatbaseName

    , SCHEMA_NAME(O.Schema_ID) AS SchemaName

    , OBJECT_NAME(I.object_id) AS TableName

    , I.NAME AS IndexName

FROM sys.indexes I INNER JOIN sys.objects O ON I.object_id = O.object_id

LEFT OUTER JOIN sys.dm_db_index_usage_stats S ON S.object_id = I.object_id

        AND I.index_id = S.index_id

        AND DATABASE_ID = DB_ID()

WHERE OBJECTPROPERTY(O.object_id,''IsMsShipped'') = 0

  AND I.name IS NOT NULL

  AND S.object_id IS NULL'

SELECT * FROM #TempNeverUsedIndexes

ORDER BY DatbaseName, SchemaName, TableName, IndexName

DROP TABLE #TempNeverUsedIndexes

结果如图:

这类索引应该小心对待，不能一概而论，要看是什么原因导致这种问题

查看索引统计的相关信息

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED

SELECT

    ss.name AS SchemaName

    , st.name AS TableName

    , s.name AS IndexName

    , STATS_DATE(s.id,s.indid) AS 'Statistics Last Updated'

    , s.rowcnt AS 'Row Count'

    , s.rowmodctr AS 'Number Of Changes'

    , CAST((CAST(s.rowmodctr AS DECIMAL(28,8))/CAST(s.rowcnt AS

DECIMAL(28,2)) * 100.0)

                             AS DECIMAL(28,2)) AS '% Rows Changed'

FROM sys.sysindexes s

INNER JOIN sys.tables st ON st.[object_id] = s.[id]

INNER JOIN sys.schemas ss ON ss.[schema_id] = st.[schema_id]

WHERE s.id > 100

  AND s.indid > 0

  AND s.rowcnt >= 500

ORDER BY SchemaName, TableName, IndexName

结果如下:

因为查询计划是根据统计信息来的，索引的选择同样取决于统计信息，所以根据统计信息更新的多寡可以看出数据库的大体状况，20%的自动更新对于大表来说非常慢。

巴特西

有关索引的DMV（转）

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