Events may appear out of sequence when using allEvents instead of eventsByPersistenceId

[mkurth]

We have the problem, that we persist a lot of events in parallel, which will sometimes cause events with a higher sequence number to be inserted before a lower one.

So we have in our collection something like:

{.. from: 1 ..}, {.. from: 2 ..}, {.. from: 3 ..}, {.. from: 5 ..}, {.. from: 4 ..}

This is no problem, when we use readJournal.eventsByPersistenceId() which uses a sort before running the RemoveDuplicatedEventsByPersistenceId.
But readJournal.allEvents() is missing a sort an therefore in the above case we would lose Event 4.

I'm not sure if we're doing something wrong (we're pretty new to CQRS + ES) or if this is a problem.

BTW we're using casbah as backend

[scullxbones]

Hi @mkurth

You're correct in that allEvents() uses no sort on sequenceNr. This means that it's not suitable for a use case that requires events to iterate in a sequenceNr order. I don't think it's accurate to say the events disappear, so i'm changing the title to reflect what you're saying above. There's a ticket to add a global ordering counter #95, but that work hasn't started yet.

Thanks!