带有选项的无限循环CTE（最大递归0）

问题描述

我有大量记录的CTE查询。以前它工作正常。但是最近，它对某些成员抛出了错误

I have CTE query with large record on it. Previously it worked fine. But lately, it throws an error for some members

所以我放了 OPTION（最大递归0）或 OPTION（maxrecursion 32767），因为我不想限制记录。但是，结果是查询需要永远加载。我该怎么解决？

So I put OPTION (maxrecursion 0) or OPTION (maxrecursion 32767) on my query, because I don't want to limit the records. But, the result is the query takes forever to load. How do I solve this?

这是我的代码：

with cte as(
-- Anchor member definition
    SELECT  e.SponsorMemberID , e.MemberID, 1 AS Level
    FROM tblMember AS e
    where e.memberid = @MemberID

union all

-- Recursive member definition
    select child.SponsorMemberID , child.MemberID, Level + 1
    from tblMember child

join cte parent

on parent.MemberID = child.SponsorMemberID
)
-- Select the CTE result
    Select distinct a.*
    from cte a
    option (maxrecursion 0)

编辑：易于理解的代码

已解决：因此，问题不是出自 maxrecursion 。来自CTE。我不知道为什么，但可能包含任何赞助者周期：A-> B-> C-> A-> ...（感谢@HABO）

SOLVED: So the issue is not came from maxrecursion. It's from the CTE. I don't know why but possibly it contain any sponsor cycles: A -> B -> C -> A -> ... (Thanks to @HABO)

我试过这种方法，它的工作原理。

I tried this method and it works. Infinite loop in CTE when parsing self-referencing table

推荐答案

如果您要达到递归限制，那么您在赞助关系或数据循环方面都具有相当大的深度。像下面这样的查询将检测循环并终止递归：

If you are hitting the recursion limit, you either have considerable depth in sponsoring relationships or a loop in the data. A query like the following will detect loops and terminate the recursion:

declare @tblMember as Table ( MemberId Int, SponsorMemberId Int );
insert into @tblMember ( MemberId, SponsorMemberId ) values
  ( 1, 2 ), ( 2, 3 ), ( 3, 5 ), ( 4, 5 ), ( 5, 1 ), ( 3, 3 );
declare @MemberId as Int = 3;
declare @False as Bit = 0, @True as Bit = 1;

with Children as (
  select MemberId, SponsorMemberId,
    Convert( VarChar(4096), '>' + Convert( VarChar(10), MemberId ) + '>' ) as Path, @False as Loop
    from @tblMember
    where MemberId = @MemberId
  union all
  select Child.MemberId, Child.SponsorMemberId,
    Convert( VarChar(4096), Path + Convert( VarChar(10), Child.MemberId ) + '>' ),
    case when CharIndex( '>' + Convert( VarChar(10), Child.MemberId ) + '>', Path ) = 0 then @False else @True end
    from @tblMember as Child inner join
      Children as Parent on Parent.MemberId = Child.SponsorMemberId
    where Parent.Loop = 0 )
  select *
    from Children
    option ( MaxRecursion 0 );

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