Azure上的SQL递归CTE超时

Question

我有以下视图，它在Azure上运行时存在严重的性能问题。如果我在本地复制Azure数据库并在视图上运行任何查询，它会在几秒钟内返回。对视图的同一查询在Azure上超时。

为什么针对视图的查询会在Azure上超时？

  CREATE VIEW [dbo].[JobTypeDescendantJobTypes] 
      AS 
      WITH cte (ParentJobTypeId, Id) 
         AS (SELECT Id , 
            Id 
          FROM  dbo.JobTypes 
          UNION ALL 
          SELECT e.Id , 
            cte.Id 
          FROM  cte 
            INNER JOIN dbo.JobTypes AS e ON e.ParentJobTypeId = cte.ParentJobTypeId 
         ) 
      SELECT ISNULL(Id, 0) AS ParentJobTypeId, 
        ISNULL(ParentJobTypeId, 0) AS Id 
      FROM cte 

Answer 1

重建您的统计/索引。要做到这一点

的一种方法是：（*注意：在生产运行慎用）

DECLARE @table nvarchar(255) 
DECLARE tablecursor CURSOR FOR 
SELECT table_name FROM information_schema.tables WHERE table_type = 'base table' 

OPEN tablecursor 
FETCH NEXT FROM tablecursor INTO @table 

WHILE @@FETCH_STATUS = 0 
BEGIN 
    exec('ALTER INDEX ALL ON ' + @table + ' REBUILD') 
    FETCH NEXT FROM tablecursor INTO @table 
END 

CLOSE tablecursor 
DEALLOCATE tablecursor