[Monetdb-developers] About MonetDB's modules

Rodrigo Schmidt rodrigo.schmidt at epfl.ch
Wed Jun 1 20:40:35 CEST 2005


Hi Niels (and others),

Thank you very much for the help.

> 
> The MonetDB/MIL server indeed only comes with the handles to build 
> transaction support (such as locking etc). The SQL server complements 
> this with full transaction support. This is based on Optimistic Concurrency
> Control. A transaction simply starts and at the end checks the used columns 
> where not changed by other transactions during its lifetime.
> All changes are then logged to a writeahead log and once this is completed
> the 'commit' is done.
> 

Does this mean that a transaction can be aborted by the time the client 
issues a commit request??

Wasn't it better to implement classic 2PL (two-phase locking) for an 
MMDB? At least the early papers in main memory databases advocate using 
simple 2PL with coarse lock granularity, since transactions execute 
faster and concurrency becomes less important.

Thanks,
Rodrigo




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