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人人都是 DBA（XIII）索引信息收集脚本汇编

什么？有个 SQL 执行了 8 秒！

哪里出了问题？臣妾不知道啊，得找 DBA 啊。

DBA 人呢？离职了！！擦！！！

程序员在无处寻求帮助时，就得想办法自救，努力让自己变成 "伪 DBA"。

索引

找出哪些表的 Index 需要改进

SELECT CONVERT(DECIMAL(18, 2), user_seeks * avg_total_user_cost * (avg_user_impact * 0.01)) AS [index_advantage]
    ,migs.last_user_seek
    ,mid.[statement] AS [Database.Schema.Table]
    ,mid.equality_columns
    ,mid.inequality_columns
    ,mid.included_columns
    ,migs.unique_compiles
    ,migs.user_seeks
    ,migs.avg_total_user_cost
    ,migs.avg_user_impact
FROM sys.dm_db_missing_index_group_stats AS migs WITH (NOLOCK)
INNER JOIN sys.dm_db_missing_index_groups AS mig WITH (NOLOCK) ON migs.group_handle = mig.index_group_handle
INNER JOIN sys.dm_db_missing_index_details AS mid WITH (NOLOCK) ON mig.index_handle = mid.index_handle
ORDER BY index_advantage DESC
OPTION (RECOMPILE);

这里查询出的数据，只是说明数据寻址时间有点儿长，不一定就是缺少索引所引起的。

在指定数据库中查找哪些表的 Index 需要改进

SELECT DISTINCT CONVERT(DECIMAL(18, 2), user_seeks * avg_total_user_cost * (avg_user_impact * 0.01)) AS [index_advantage]
    ,migs.last_user_seek
    ,mid.[statement] AS [Database.Schema.Table]
    ,mid.equality_columns
    ,mid.inequality_columns
    ,mid.included_columns
    ,migs.unique_compiles
    ,migs.user_seeks
    ,migs.avg_total_user_cost
    ,migs.avg_user_impact
    ,OBJECT_NAME(mid.[object_id]) AS [Table Name]
    ,p.rows AS [Table Rows]
FROM sys.dm_db_missing_index_group_stats AS migs WITH (NOLOCK)
INNER JOIN sys.dm_db_missing_index_groups AS mig WITH (NOLOCK) ON migs.group_handle = mig.index_group_handle
INNER JOIN sys.dm_db_missing_index_details AS mid WITH (NOLOCK) ON mig.index_handle = mid.index_handle
INNER JOIN sys.partitions AS p WITH (NOLOCK) ON p.[object_id] = mid.[object_id]
WHERE mid.database_id = DB_ID()
ORDER BY index_advantage DESC
OPTION (RECOMPILE);

根据缓存的查询计划判断 SP 是否需要优化

SELECT TOP (25) OBJECT_NAME(objectid) AS [ObjectName]
    ,query_plan
    ,cp.objtype
    ,cp.usecounts
FROM sys.dm_exec_cached_plans AS cp WITH (NOLOCK)
CROSS APPLY sys.dm_exec_query_plan(cp.plan_handle) AS qp
WHERE CAST(query_plan AS NVARCHAR(MAX)) LIKE N'%MissingIndex%'
    AND dbid = DB_ID()
ORDER BY cp.usecounts DESC
OPTION (RECOMPILE);

发现那些 Index 的写远多于读的表

SELECT OBJECT_NAME(s.[object_id]) AS [Table Name]
    ,i.[name] AS [Index Name]
    ,i.index_id
    ,i.is_disabled
    ,i.is_hypothetical
    ,i.has_filter
    ,i.fill_factor
    ,user_updates AS [Total Writes]
    ,user_seeks + user_scans + user_lookups AS [Total Reads]
    ,user_updates - (user_seeks + user_scans + user_lookups) AS [Difference]
FROM sys.dm_db_index_usage_stats AS s WITH (NOLOCK)
INNER JOIN sys.indexes AS i WITH (NOLOCK) ON s.[object_id] = i.[object_id]
    AND i.index_id = s.index_id
WHERE OBJECTPROPERTY(s.[object_id], 'IsUserTable') = 1
    AND s.database_id = DB_ID()
    AND user_updates > (user_seeks + user_scans + user_lookups)
    AND i.index_id > 1
ORDER BY [Difference] DESC
    ,[Total Writes] DESC
    ,[Total Reads] ASC
OPTION (RECOMPILE);

由于对索引的写操作远多于读操作，看起来 Index 的帮助不大，但需要根据业务需求来判断是否能够 Drop 掉该索引。

查看 Index 的 Statistics 最后更新时间

SELECT SCHEMA_NAME(o.[schema_id]) + N'.' + o.[name] AS [Object Name]
    ,o.type_desc AS [Object Type]
    ,i.[name] AS [Index Name]
    ,STATS_DATE(i.[object_id], i.index_id) AS [Statistics Date]
    ,s.auto_created
    ,s.no_recompute
    ,s.user_created
    ,st.row_count
    ,st.used_page_count
FROM sys.objects AS o WITH (NOLOCK)
INNER JOIN sys.indexes AS i WITH (NOLOCK) ON o.[object_id] = i.[object_id]
INNER JOIN sys.stats AS s WITH (NOLOCK) ON i.[object_id] = s.[object_id]
    AND i.index_id = s.stats_id
INNER JOIN sys.dm_db_partition_stats AS st WITH (NOLOCK) ON o.[object_id] = st.[object_id]
    AND i.[index_id] = st.[index_id]
WHERE o.[type] IN (
        'U'
        ,'V'
        )
    AND st.row_count > 0
ORDER BY STATS_DATE(i.[object_id], i.index_id) DESC
OPTION (RECOMPILE);

参考资料：

查看哪些 Index 被修改的最频繁

SQL Server 2008 R2

SELECT TableName = OBJECT_NAME(s.[object_id])
    ,SchemaName = SCHEMA_NAME(o.[schema_id])
    ,IndexName = i.[name]
    ,user_updates
    ,i.is_primary_key
FROM sys.dm_db_index_usage_stats s
JOIN sys.objects O ON s.[object_id] = O.[object_id]
JOIN sys.indexes i ON s.[object_id] = i.[object_id]
    AND s.index_id = i.index_id
WHERE OBJECTPROPERTY(s.[object_id], 'IsMsShipped') = 0
    AND user_seeks = 0
    AND user_scans = 0
    AND user_lookups = 0
    AND i.NAME IS NOT NULL -- Ignore HEAP indexes.
ORDER BY user_updates DESC

The user_updates counter indicates the level of maintenance on the index caused by insert, update, or delete operations on the underlying table or view.

SQL Server 2012

SELECT o.[name] AS [Object Name]
    ,o.[object_id]
    ,o.type_desc
    ,s.[name] AS [Statistics Name]
    ,s.stats_id
    ,s.no_recompute
    ,s.auto_created
    ,sp.modification_counter
    ,sp.rows
    ,sp.rows_sampled
    ,sp.last_updated
FROM sys.objects AS o WITH (NOLOCK)
INNER JOIN sys.stats AS s WITH (NOLOCK) ON s.object_id = o.object_id
CROSS APPLY sys.dm_db_stats_properties(s.object_id, s.stats_id) AS sp
WHERE o.type_desc NOT IN (
        N'SYSTEM_TABLE'
        ,N'INTERNAL_TABLE'
        )
    AND sp.modification_counter > 0
ORDER BY sp.modification_counter DESC
    ,o.[name]
OPTION (RECOMPILE);

查看 Index 碎片化指数

SELECT DB_NAME(ps.database_id) AS [Database Name]
    ,OBJECT_NAME(ps.[object_id]) AS [Object Name]
    ,i.[name] AS [Index Name]
    ,ps.index_id
    ,ps.index_type_desc
    ,ps.avg_fragmentation_in_percent
    ,ps.fragment_count
    ,ps.page_count
    ,i.fill_factor
    ,i.has_filter
    ,i.filter_definition
FROM sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, N'LIMITED') AS ps
INNER JOIN sys.indexes AS i WITH (NOLOCK) ON ps.[object_id] = i.[object_id]
    AND ps.index_id = i.index_id
WHERE ps.database_id = DB_ID()
    AND ps.page_count > 2500
ORDER BY ps.avg_fragmentation_in_percent DESC
OPTION (RECOMPILE);

参考资料：

哪个 Index 上的读操作最活跃

SELECT OBJECT_NAME(s.[object_id]) AS [ObjectName]
    ,i.[name] AS [IndexName]
    ,i.index_id
    ,user_seeks + user_scans + user_lookups AS [Reads]
    ,s.user_updates AS [Writes]
    ,i.type_desc AS [IndexType]
    ,i.fill_factor AS [FillFactor]
    ,i.has_filter
    ,i.filter_definition
    ,s.last_user_scan
    ,s.last_user_lookup
    ,s.last_user_seek
FROM sys.dm_db_index_usage_stats AS s WITH (NOLOCK)
INNER JOIN sys.indexes AS i WITH (NOLOCK) ON s.[object_id] = i.[object_id]
WHERE OBJECTPROPERTY(s.[object_id], 'IsUserTable') = 1
    AND i.index_id = s.index_id
    AND s.database_id = DB_ID()
ORDER BY user_seeks + user_scans + user_lookups DESC
OPTION (RECOMPILE);

哪个 Index 上的写操作最活跃

SELECT OBJECT_NAME(s.[object_id]) AS [ObjectName]
    ,i.[name] AS [IndexName]
    ,i.index_id
    ,s.user_updates AS [Writes]
    ,user_seeks + user_scans + user_lookups AS [Reads]
    ,i.type_desc AS [IndexType]
    ,i.fill_factor AS [FillFactor]
    ,i.has_filter
    ,i.filter_definition
    ,s.last_system_update
    ,s.last_user_update
FROM sys.dm_db_index_usage_stats AS s WITH (NOLOCK)
INNER JOIN sys.indexes AS i WITH (NOLOCK) ON s.[object_id] = i.[object_id]
WHERE OBJECTPROPERTY(s.[object_id], 'IsUserTable') = 1
    AND i.index_id = s.index_id
    AND s.database_id = DB_ID()
ORDER BY s.user_updates DESC
OPTION (RECOMPILE);

查看 Index 所使用的 Buffer 数量

SELECT TOP 25 obj.[name] AS TableName
    ,i.[name] AS IndexName
    ,i.[type_desc] AS IndexType
    ,count(*) AS Buffered_Page_Count
    ,count(*) * 8192 / (1024 * 1024) AS Buffer_MB
    ,obj.index_id
FROM sys.dm_os_buffer_descriptors AS bd
INNER JOIN (
    SELECT object_name(object_id) AS NAME
        ,index_id
        ,allocation_unit_id
        ,object_id
    FROM sys.allocation_units AS au
    INNER JOIN sys.partitions AS p ON au.container_id = p.hobt_id
        AND (
            au.type = 1
            OR au.type = 3
            )
    
    UNION ALL
    
    SELECT object_name(object_id) AS NAME
        ,index_id
        ,allocation_unit_id
        ,object_id
    FROM sys.allocation_units AS au
    INNER JOIN sys.partitions AS p ON au.container_id = p.hobt_id
        AND au.type = 2
    ) AS obj ON bd.allocation_unit_id = obj.allocation_unit_id
LEFT JOIN sys.indexes i ON i.object_id = obj.object_id
    AND i.index_id = obj.index_id
WHERE database_id = db_id()
GROUP BY obj.NAME
    ,obj.index_id
    ,i.[name]
    ,i.[type_desc]
ORDER BY Buffered_Page_Count DESC

按照 IO Latch 等待请求对索引进行排行

SELECT OBJECT_SCHEMA_NAME(ios.object_id) + '.' + OBJECT_NAME(ios.object_id) AS table_name
    ,i.[name] AS index_name
    ,page_io_latch_wait_count
    ,page_io_latch_wait_in_ms
    ,CAST(1. * page_io_latch_wait_in_ms / NULLIF(page_io_latch_wait_count, 0) AS DECIMAL(12, 2)) AS page_io_avg_lock_wait_ms
    ,page_latch_wait_count
    ,page_latch_wait_in_ms
    ,CAST(1. * page_latch_wait_in_ms / NULLIF(page_latch_wait_count, 0) AS DECIMAL(12, 2)) AS page_avg_lock_wait_ms
FROM sys.dm_db_index_operational_stats(DB_ID(), NULL, NULL, NULL) ios
INNER JOIN sys.indexes i ON i.object_id = ios.object_id
    AND i.index_id = ios.index_id
WHERE OBJECTPROPERTY(ios.object_id, 'IsUserTable') = 1
ORDER BY 3 DESC

《人人都是 DBA》系列文章索引：

序号	名称
1	人人都是 DBA（I）SQL Server 体系结构
2	人人都是 DBA（II）SQL Server 元数据
3	人人都是 DBA（III）SQL Server 调度器
4	人人都是 DBA（IV）SQL Server 内存管理
5	人人都是 DBA（V）SQL Server 数据库文件
6	人人都是 DBA（VI）SQL Server 事务日志
7	人人都是 DBA（VII）B 树和 B+ 树
8	人人都是 DBA（VIII）SQL Server 页存储结构
9	人人都是 DBA（IX）服务器信息收集脚本汇编
10	人人都是 DBA（X）资源信息收集脚本汇编
11	人人都是 DBA（XI）I/O 信息收集脚本汇编
12	人人都是 DBA（XII）查询信息收集脚本汇编
13	人人都是 DBA（XIII）索引信息收集脚本汇编
14	人人都是 DBA（XIV）存储过程信息收集脚本汇编
15	人人都是 DBA（XV）锁信息收集脚本汇编

查看全文

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原文地址：https://www.cnblogs.com/firstdream/p/7979039.html