3 ms·
> Okay. I open a transaction for three days (let's say indefinitely), maybe reading a few tuples here and there and updating a few, but never committing. How do
by haberman 14y ago
> Okay. I open a transaction for three days (let's say indefinitely), maybe reading a few tuples here and there and updating a few, but never committing. How does this system not fall over?
They say they use optimistic concurrency control, so your writers aren't taking any locks, instead the transaction will just fail when you commit if any of your read/modify/write's were modified in the meantime.
- fdr 14y agoAh. So that probably means a consistent copy or backup is probably practically impossible.
- asto 14y agoUnless it locks when backing up or copying?
- fdr 14y agoYes. But then the data is not available or other transactions will fail to commit during a long backup operation, and most people don't like that.
- viraptor 14y agoThey do list in features: > Coming soon. An integrated backup system provides a true "moment-in-time" snapshot backup of the entire distributed database stored to a remote file system on a schedule.
- thebigjc 14y agoSnapshops / backups with MVCC isn't that complicated - you take a snapshot of the versions, and then backup the data at that version.
- fdr 14y agoIt is not complex, but it is very burdensome, usually because various garbage collection processes cannot act as long as the long snapshot is open.