为什么我的 SP_HELPINDEX 显示了很多索引？

Question

使用sp_helpindex My_table我有这个列表：

但我的表只有这些索引：

为什么会这样？我正在使用查询在特定表中搜索“相等索引”。这个查询返回了很多我什至没有在表中的索引。

WITH IndexColumns AS (
SELECT '[' + s.Name + '].[' + T.Name + ']' AS TableName,
i.name AS IndexName,  C.name AS ColumnName, i.index_id,ic.index_column_id,
COUNT(*) OVER(PARTITION BY t.OBJECT_ID, i.index_id) AS ColCount
FROM sys.schemas AS s
JOIN sys.tables AS t ON t.schema_id = s.schema_id
JOIN sys.indexes AS i ON I.OBJECT_ID = T.OBJECT_ID
JOIN sys.index_columns AS IC ON  IC.OBJECT_ID = I.OBJECT_ID
AND IC.index_id = I.index_id
JOIN sys.columns AS C ON  C.OBJECT_ID = IC.OBJECT_ID
AND C.column_id = IC.column_id
WHERE IC.is_included_column = 0
)
SELECT DISTINCT a.TableName, a.IndexName AS Index1, b.IndexName AS Index2
FROM IndexColumns AS a
JOIN IndexColumns AS b ON b.TableName = a.TableName
AND b.IndexName <> a.IndexName
AND b.index_column_id = a.index_column_id
AND  b.ColumnName = a.ColumnName
AND a.index_column_id < 3
AND a.index_id < b.index_id
AND a.ColCount <= B.ColCount
ORDER BY a.TableName, a.IndexName;

这些索引从何而来？

Answer 1

您看到的索引是hypothetical indexes由数据库引擎优化顾问创建的。

DTA 如果它崩溃或者你因为它运行时间太长而杀死它，则会留下一些混乱。

它们都包含_dta_在名称中，您可以hypothetical在描述中看到。

试试Brent的查询，因为您很可能在其他表上也有一些这样的查询。

WITH hi AS (
SELECT QUOTENAME(SCHEMA_NAME(o.[schema_id])) +'.'+ QUOTENAME(OBJECT_NAME(i.[object_id])) AS [Table] , QUOTENAME([i].[name]) AS [Index_or_Statistics], 1 AS [Type]
FROM sys.[indexes] AS [i]
JOIN sys.[objects] AS [o]
ON i.[object_id] = o.[object_id]
WHERE 1=1 
AND INDEXPROPERTY(i.[object_id], i.[index_id], 'IsHypothetical') = 1
AND OBJECTPROPERTY([o].[object_id], 'IsUserTable') = 1

UNION ALL

SELECT QUOTENAME(SCHEMA_NAME(o.[schema_id])) +'.'+ QUOTENAME(OBJECT_NAME(o.[object_id])) AS [Table], QUOTENAME([s].[name]) AS [Index_or_Statistics], 2 AS [Type]
FROM sys.[stats] AS [s]
JOIN sys.[objects] AS [o]
ON [o].[object_id] = [s].[object_id]
WHERE [s].[user_created] = 0
AND [o].[name] LIKE '[_]dta[_]%'
AND OBJECTPROPERTY([o].[object_id], 'IsUserTable') = 1
)
SELECT [hi].[Table] ,
       [hi].[Index_or_Statistics] ,
       CASE [hi].[Type] 
       WHEN 1 THEN 'DROP INDEX ' + [hi].[Index_or_Statistics] + ' ON ' + [hi].[Table] + ';'
       WHEN 2 THEN 'DROP STATISTICS ' + hi.[Table] + '.' + hi.[Index_or_Statistics] + ';'
       ELSE 'DEAR GOD WHAT HAVE YOU DONE?'
       END AS [T-SQL Drop Command]
FROM [hi]

你应该删除它们，它们无论如何都不会被使用

编辑： 不知道为什么，但 OP 对布伦特的查询有问题，这个选择适用于他的环境

SELECT t2.NAME AS table_name
    ,t1.NAME AS index_name
FROM sys.indexes t1
INNER JOIN sys.tables t2 ON t2.object_id = t1.object_id
WHERE t2.NAME = 'MyTable'
    AND t1.NAME LIKE '%_dta_%'
    AND t1.is_hypothetical = 1