Improved optimistic versioning of event stream append operations

[ricardoduncan]

How does one trigger the expected version check that prevents appending to an event stream if the version after the Append call does not match that supplied?

I have tried faking the stream version in the mt_streams table, but this does not cause the assertion to occur.

I can see the version check is not being performed in any of the database functions either. This is an important evaluation criteria for me in terms of using Marten as an event store.

[jeremydmiller]

@ricardoduncan Meh, I see that it's missing from the docs. See the tests for an example of how to use that: https://github.com/JasperFx/marten/blob/master/src/Marten.Testing/Events/asserting_on_expected_event_version_on_append.cs

The actual assertion is done in C# code

[jokokko]

@ricardoduncan, @jeremydmiller hmm, should be documented (I have a vague memory of writing something brief): http://jasperfx.github.io/marten/documentation/events/appending/, under Appending & Assertions.

[jeremydmiller]

I'm giving this a rename today.

[oskardudycz]

@jeremydmiller could you elaborate what you'd like to change in the current mechanism?

[jeremydmiller]

I don't have anything specific in mind yet, just sounds like we need to make it easier to use. Might be mostly docs. Could help to have a way to issue read locks for better concurrency.

[oskardudycz]

Ah ok, I think that it should be mostly docs. In my previous project, we tried hard with @tpodolak to break it but weren't able 😉

Maybe we could check the sequence issues that @jacobpovar had.