[mysql-dde] Re: The mutual conflict problem

  • From: "Fabricio Mota" <fabricio.oliveira@xxxxxxxxxxxxxxxx>
  • To: <mysql-dde@xxxxxxxxxxxxx>
  • Date: Mon, 12 Dec 2005 13:51:26 -0200

Oh, man, I have a problem, because here from my work I can't access 
Internet, just at home, tonight (now it's 13:50 (=1:50 pm). Couldn't you 
send it for me via e-mail?

----- Original Message ----- 
From: "Peter B. Volk" <PeterB.Volk@xxxxxxx>
To: <mysql-dde@xxxxxxxxxxxxx>
Sent: Monday, December 12, 2005 1:01 PM
Subject: [mysql-dde] Re: The mutual conflict problem


> Ok I guess the list strips the images down:
>
> here are the links:
>
> www.inf.tu-dresden.de/~s7205538/dde/unique_management.jpg
> www.inf.tu-dresden.de/~s7205538/dde/unique_management_sequenc.jpg
>
> Peter
> ----- Original Message ----- 
> From: "Peter B. Volk" <PeterB.Volk@xxxxxxx>
> To: <mysql-dde@xxxxxxxxxxxxx>
> Sent: Monday, December 12, 2005 3:56 PM
> Subject: [mysql-dde] Re: The mutual conflict problem
>
>
>> Hey,
>> Well I could be solved by having GI-Key Masters. I've added 2 diagramms 
>> to
>> show a few details.
>>
>> Peter
>> ----- Original Message ----- 
>> From: "Fabricio Mota" <fabricio.oliveira@xxxxxxxxxxxxxxxx>
>> To: "dde" <mysql-dde@xxxxxxxxxxxxx>
>> Sent: Monday, December 12, 2005 2:19 PM
>> Subject: [mysql-dde] The mutual conflict problem
>>
>>
>> > Hey Guy!
>> > We have a problem with uniqueness management with any approach we use.
>> That is:
>> >
>> > Suppose Clients C1 and C2, connected respectivelly through servers S1
> and
>> S2.
>> > Both clients try to insert a value k, into a unique-indexed column.
>> Suppose they try to insert the value approximately during the same time.
>> >
>> > If we think about to validate global uniqueness among servers before to
>> insert, then:
>> >
>> > 1 - C1 tries to insert it through S1 / at same time, C2 tries it 
>> > through
>> S2.
>> > 2 - S1 validates k / C1 locally. Uniqueness is ok. S2 validates k / C2
>> locally, too. Both are ok.
>> > 3 - S1 request S2 about uniqueness of k. At aproximately the same time,
> S2
>> request the same for S1.
>> > 4a - if we consider a fully isolated transaction approach, then S1 will
>> perform C1 command, and S2 will perform C2 command, too. That's an
>> inconsistence!
>> > 4b - if we consider the value k is shared during transactions, both
>> servers will abort, because k is already there during remote validation,
>> causing a mutual abort.
>> >
>> > If we think about to validate global uniqueness among servers after to
>> insert, replicating global indexes, then:
>> >
>> > 1 - C1 tries to insert it through S1 / at same time, C2 tries it 
>> > through
>> S2.
>> > 2 - S1 validates k / C1 locally. Uniqueness is ok. S2 validates k / C2
>> locally, too. Both are ok.
>> > 3 - S1 tries to sync S2 about its new value k. At aproximately the same
>> time, S2 tries to sync S1, too.
>> > 4a - if we consider a fully isolated transaction approach, then S1 will
>> update S2 with its k, and S2 will update S1 with its own k, too. That's 
>> an
>> inconsistence, again.
>> > 4b - if we consider the value k is shared during transactions, both
>> servers will abort, because k is already there during remote validation,
>> causing a mutual abort.
>> >
>> > If we consider the hypothesis 4b, what criterion could be used for both
>> server to agree in which transaction to abort?
>> >
>> > Or so, what could we do in respect to it?
>> >
>> > Fabricio Mota
>> > Analista de Sistemas
>> > FCPC - Divisão de Planejamento do Cadastro Comercial
>> > MySql-DDE discussion list
>> > www.freelists.org/
>> >
>>
>>
>>
>>
>> MySql-DDE discussion list
>> www.freelists.org/
>>
>
> MySql-DDE discussion list
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>
> 

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