在缓存的执行计划中寻找缺失的索引

Question

我有以下查询向我显示了 sql server 中缓存的内容：

SELECT cp.objtype AS ObjectType,
OBJECT_NAME(st.objectid,st.dbid) AS ObjectName,
cp.usecounts AS ExecutionCount,
st.TEXT AS QueryText,
qp.query_plan AS QueryPlan
FROM sys.dm_exec_cached_plans AS cp
CROSS APPLY sys.dm_exec_query_plan(cp.plan_handle) AS qp
CROSS APPLY sys.dm_exec_sql_text(cp.plan_handle) AS st
WHERE 1=1
  --AND OBJECT_NAME(st.objectid,st.dbid) = 'YourObjectName'
  AND query_plan IS NOT NULL
ORDER BY ExecutionCount DESC

有没有办法可以查询 queryPlan 字段以查找丢失的索引？

Answer 1

您可以尝试执行以下脚本并从此处查找缓存执行计划中丢失的索引

SELECT qp.query_plan
, total_worker_time/execution_count AS AvgCPU 
, total_elapsed_time/execution_count AS AvgDuration 
, (total_logical_reads+total_physical_reads)/execution_count AS AvgReads 
, execution_count 
, SUBSTRING(st.TEXT, (qs.statement_start_offset/2)+1 , ((CASE qs.statement_end_offset WHEN -1 THEN datalength(st.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2) + 1) AS txt 
, qp.query_plan.value('declare default element namespace "http://schemas.microsoft.com/sqlserver/2004/07/showplan"; (/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple/QueryPlan/MissingIndexes/MissingIndexGroup/@Impact)[1]' , 'decimal(18,4)') * execution_count AS TotalImpact
, qp.query_plan.value('declare default element namespace "http://schemas.microsoft.com/sqlserver/2004/07/showplan"; (/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple/QueryPlan/MissingIndexes/MissingIndexGroup/MissingIndex/@Database)[1]' , 'varchar(100)') AS [DATABASE]
, qp.query_plan.value('declare default element namespace "http://schemas.microsoft.com/sqlserver/2004/07/showplan"; (/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple/QueryPlan/MissingIndexes/MissingIndexGroup/MissingIndex/@Table)[1]' , 'varchar(100)') AS [TABLE]
FROM sys.dm_exec_query_stats qs
cross apply sys.dm_exec_sql_text(sql_handle) st
cross apply sys.dm_exec_query_plan(plan_handle) qp
WHERE qp.query_plan.exist('declare default element namespace "http://schemas.microsoft.com/sqlserver/2004/07/showplan";/ShowPlanXML/BatchSequence/Batch/Statements/StmtSimple/QueryPlan/MissingIndexes/MissingIndexGroup/MissingIndex[@Database!="m"]') = 1
ORDER BY TotalImpact DESC

它在 sql server 2008 和 2012 中对我有用，但您仍然需要检查它是否像您在 sql server 2014 中看到的那样工作。

还，

除了上述内容之外，我建议您阅读查找计划缓存中哪些查询使用特定索引，这是 Jonathan 的一个很棒的脚本，它确实有助于理解用于缓存中当前执行计划的索引的用法。