[Monetdb-developers] MapiClient asynchronous interface?

Martin Kersten Martin.Kersten at cwi.nl
Sat Nov 18 19:44:27 CET 2006

Johann Borck wrote:
> Fabian Groffen wrote:
>> Ok, but in this situation, it looks to me as if you would benefit from a
>> "real" embedded version of MonetDB, where you just talk to a library
>> instead, omitting all costs of Mapi/TCP and simply stick to method calls.
> Is this what's mentioned in the docs/examples as embedded mode, or even
> lower level? I thought about using it embedded, but what scared me a bit
> is that locking is turned of completely when using it this way, and so
> big transactions could make smaller ones wait. OTOH real big
> transactions are not very probable for my usecase and the embedded
> version is probably very very fast :). 
Indeed the embedded version was originally carved out to run on a
SBC Linux board of an MP3 player. Transactions came from a single user.
Concurrency control overhead could raise to >30% of all cpu cycles.

If your usecase has the option to differentiate short/long transactions
then you might consider a queuing scheme, postponing the long ones.
Or, alternatively, break the long one semantically into independent pieces.

If your database fits in memory, I would definitely look at serial execution
as the way to go and counter overload by an admission policy.

>> Is asynchronous equal to non-blocking IO in your case?  The latter one
>> should be too hard, I suppose...
> Yep, it implies non-blocking IO. All right.. I think first I should see
> how the embedded stuff works out.  thanks for the suggestion,
> Johann
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