[Monetdb-developers] About MonetDB's modules

Rodrigo Schmidt rodrigo.schmidt at epfl.ch
Wed Jun 1 21:30:01 CEST 2005


Hi,

> Indeed, but also 'classic 2PL' can still abort (allthough only because
> of completely different reasons).

Sure, but the spurious aborts should happen more often with OCC. 
Moreover, the reason why transactions are aborted using OCC renders a 
database replication algorithm more complex.

> The current 'occ' usually works well, ie no lock overhead and no deadlock
> detection. Also the current scheme has a very simple 'abort',ie just throw away
> the current copies. But I agree its far from perfect and we have started 
> some work on a 'simple' lock based version.

Do you have any idea of when this new module will be finished? I will 
probably have to write some simple 2PL mechanism to use MonetDB with our 
replication protocols. I do not intend to cover deadlock detection but 
since I am not used to Monet's structure and sources, it might take a 
while until I get it finished working alone. If you have plans to finish 
it soon, I could try to help you to get it done faster.

BTW, here are two questions I sent to Martin Kersten and forgot to 
forward to the developers list. Actually I changed them a little bit as 
a result of your previous answers

First, is it easy (feasible) to write a module to extend the kernel and 
provide consistent snapshots for read-only transactions while update 
transactions execute without blocking?

Second, is there a simple way to bypass Mapi and submit SQL requests 
directly to the server's SQL front-end without the cost of a socket 
connection?

Thanks again for the help.

All the best,
Rodrigo




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