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From:Kevin Lewis Date:January 19 2009 4:58pm
Subject:Re: When you have a chance...
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Chris,

I thought a lot about this solution the last couple of days.  Using a 
timeout as a standard expected event in handling a concurrency issue is 
not the best approach, I'm sure Jim would agree.

But there are extenuating circumstances.  You have shown that we need to 
protect other threads that call hasData() from calling that concurrently 
with an active chill thread because it could be there in one instant and 
not the next. The act of chilling a record is very intrusive and 
dangerous without a record mutex.  But using a record mutex is against 
Jim's MVCC philosophy for many reasons which need not be listed here. We 
just can't do it.  So testing and using the syncPrior as an alternative 
to the record mutex is OK, I think.  Especially since there is no hard 
requirement to chill any particular record.

Since the action on the record is not  required, and chilling should not 
happen very often, I think a timeout and move-on approach is acceptable 
here.

Especially since I cannot think of a better approach! :)

Jim, this is your invitation to spark a better idea, or think of a 
better approach.  Note that this use of syncPrior during a chill 
actually works, even though it is not pretty.

Kevin

Christopher Powers wrote:
> ...call me today 612-729-1519 or my cell, 612-616-1069. I'd like to 
> discuss the changes I did for garbage collect.
> 
> I pushed the fixes to mysql-6.0-falcon-chris on PB2, and *both* 
> falcon_online_alter and falcon_chill_thaw passed. I find this to be very 
> encouraging.
> 
> Using syncPrior in chill was not straightforward solution because of a 
> deadlock with a low-level thaw, but what I have works.
> 

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Thread
Re: When you have a chance...Kevin Lewis19 Jan
  • Re: When you have a chance...Jim Starkey19 Jan
    • Re: When you have a chance...Kevin Lewis20 Jan
      • Re: When you have a chance...Christopher Powers20 Jan
      • Re: When you have a chance...Jim Starkey20 Jan
        • Re: When you have a chance...Kevin Lewis21 Jan
      • Re: When you have a chance...Jim Starkey21 Jan
        • Re: When you have a chance...Kevin Lewis21 Jan
          • RE: When you have a chance...Vladislav Vaintroub21 Jan
            • Re: When you have a chance...Jim Starkey21 Jan
            • Re: When you have a chance...Kevin Lewis21 Jan