带有选项的无限循环 CTE (maxrecursion 0) [英] Infinite loop CTE with OPTION (maxrecursion 0)

问题描述

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

The statement terminated. The maximum recursion 100 has been exhausted before statement completion.

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?

Here's my code:

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)

EDIT: remove unnecessary code to easy understand

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)

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

解决方案

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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