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SQL Server 2008上的游标性能问题

Victoria625_176 发布于 2023-02-12 16:35

我有一个遗留存储过程试图创建一个光标来遍历查询中的每一行.表现非常糟糕.然后我检查查询计划,大部分成本(> 47%)都在一个对象上[tempdb].[CWT_PrimaryKey].此对象由存储过程中创建的游标创建.不确定如何提高此案例的性能,因为在tempdbSQL Server创建的此对象上无法执行任何操作.

存储过程中的伪代码如:

BEGIN TRY
  BEGIN TRANSACTION

  declare mycusorr local fast_forward
        for SELECT *  From MyTab Where a=b;
  open mycusorr; 
  fetch next from mycusorr into @v1, @v2, ...;

  while @@fetch_status = 0
    begin
      --some query to check rules from different tables
      Update AnotherTab Set column=value where id = @v1;
      if (there is error)
         insert error to error user log table;

  End

  close mycusorr; 
  deallocate mycusorr; 

  COMMIT;
END TRY
BEGIN CATCH
  close mycusorr; 
  deallocate mycusorr; 
  SELECT ERROR_NUMBER() AS ErrorNumber,ERROR_MESSAGE() AS ErrorMessage;    
  ROLLBACK TRAN;    
END CATCH

没有主键MyTab,但在条件中使用的列上创建了索引.

大约有10,000行Mytab.运行存储过程需要3个多小时甚至没有完成.如果我从存储过程中删除事务,它将是快速的.

当我检查锁定时SP_lock,在循环中具有update子句的表的键或页面上有超过1万个X或IX锁.

1 个回答

怎么样:

UPDATE t SET t.column = m.value
  FROM dbo.AnotherTab AS t
  INNER JOIN dbo.MyTab AS m
  ON t.id = ... no idea what the join criteria is because your cursor uses SELECT *
  WHERE m.a = m.b; -- I also don't think this is described well enough to guess

如果您提供真实代码而不是伪代码,您可以获得更多,更好,更好的答案.

2023-02-12 16:37 回答

中国人TM

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