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From Mike Matrigali <mikem_...@sbcglobal.net>
Subject Re: Releasing latches when waiting for locks. When and why?
Date Mon, 20 Nov 2006 18:33:18 GMT
Bryan is right.  This is exactly the kind of access that Btree's need,
and why the interface was there in the first place.  My dim memory is
that for some reason it didn't work right for btree's so btree's
hand coded it - but now I don't remember the details.

Bryan Pendleton wrote:
>> When this method is used, the specified latch will be
>> released if the lock cannot be obtained immediately, and that page
>> will be re-latched when the lock has been obtained.
> 
> 
> I'm just guessing here ...
> 
> I think that there are some fairly advanced Btree traversal algorithms,
> in particular situations in which you are reading backward through a
> Btree which may be undergoing concurrent structural modifications by
> others, in which a primitive operation like the one you describe is 
> crucial.
> 
> So perhaps this method was included in the Store in preparation for some
> access method techniques which haven't yet been implemented?
> 
> thanks,
> 
> bryan
> 
> 
> 
> 


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