2011/4/22 Branko Čibej <br...@e-reka.si>: > On 22.04.2011 23:11, Hyrum K Wright wrote: >> What's the relationship between cancellation functions and >> transactions in wc-ng? >> >> In the interests of performance and correctness, we've been moving >> toward a model where more and more gets done in a single wc-ng >> transaction. I've no problem with that, and like the atomicity and >> speed it gives us, but how does that interact with our cancellation >> functions? Do we still check for cancellation from within the >> transaction? If the user cancels, do we rollback the transaction, or >> commit it? >> >> My question then is two-fold: >> * what actually happens today? >> * and what is the Right Thing to happen? >> >> My own thoughts: we should check for cancellation, and if it occurs, >> we should rollback the txn. > > If the transaction is so long-running that cancellation checks would > make sense ... then something's wrong, as AFAIUI long-running > transactions are frowned upon around here. Still, if that does happen, > then the only thing you can do when an operation is canceled is to roll > back the transaction -- anything else would be bound to produce invalid > state in the database.
I would tend to agree on both points, and I also wonder if/how our cancellation checks and handlers become a bit obsolete with atomic database operations (which execute in only a few queries, rather than a multitude of tree walks). -Hyrum
