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JasperFx/marten

Postgresql as a Document Database and Event Store for .Net Applications

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Jan 29 21:19

darena-pjindal opened #2474
Jan 29 21:19

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Jan 25 17:57

appetere commented #2421
Jan 25 17:57

appetere commented #2421

Oskar Dudycz

@oskardudycz

Thanks, Willem, for the feedback! Happy that you like it 🙂 I saw your comment on the Youtube video and answered it, but as an added link, there Youtube spam filters blocked me 🤷‍♂️

I linked the self-paced kit exercise showing different flours of handling domain logic with Marten https://github.com/oskardudycz/EventSourcing.NetCore/tree/main/Workshops/IntroductionToEventSourcing/08-BusinessLogic.Marten 🙂

Willem Meints

@wmeints

Kewl! I'm using some of the tricks with records in projections that you showed. Makes it more readable :D

Oskar Dudycz

@oskardudycz

Yeah, I like that it’s so self-explanatory. In projections (compared to aggregation) you get less performance penalty

Willem Meints

@wmeints

The only thing that still has me pondering is this: What if I want to call other dependencies (especially scoped ones) from a projection? Is that a thing?

Oskar Dudycz

@oskardudycz

That’s doable, see https://github.com/oskardudycz/EventSourcing.NetCore/blob/main/Core.Marten/Config.cs#L73

And https://github.com/oskardudycz/EventSourcing.NetCore/blob/main/Core.Marten/Subscriptions/MartenEventPublisher.cs#L27

Willem Meints

@wmeints

Doesn't look too bad. Thanks for sharing :-)

Oskar Dudycz

@oskardudycz

Best to probably inject factory Func<YourDependency> doing the scope creation and resolution

from ServiceProvider

Although it’s best to be careful and avoid such need ;)

Willem Meints

@wmeints

Yeah, that's what I'm thinking as well. There are better, more visible spots, to do these kinds of things. The less magic, the better.

Oskar Dudycz

@oskardudycz

I tried to do that in the past, even introducing syntactic sugar on top of it in Marten as one of my first PRs, but at some point dropped using it ;)

Using external dependencies introduced deterministic behaviours and performance degradation in our case.

Of course, sometimes it’s right and justified, but it better double-check if it’s really needed.

Phillip Haydon

@phillip-haydon

thanks for the recordings @oskardudycz, plan to watch tomorrow, my daughter was born yesterday so in hospital with wife with a bit of free time

Oskar Dudycz

@oskardudycz

Congratulations Phillip! I hope that's all fine :)

Jeremy D. Miller

@jeremydmiller

Oh wow, congrats Phillip! Hope everybody is doing well

Babu Annamalai

@mysticmind

Congrats @phillip-haydon!

Jeremy D. Miller

@jeremydmiller

@oskardudycz @mysticmind I'm piddling around w/ minor document updates today and maybe this weekend. The newish FetchForWriting() functionality? Would you all rather have that added to the existing appending web page, or an all new page?

I'm leaning toward an all new page that's dedicated to handling CQRS commands, but I'd be very happy to have any suggestions for what that page would even be called

Phillip Haydon

@phillip-haydon

Thanks. Mum and baby are doing really well.

Oskar Dudycz

@oskardudycz

Great Phillip, keeping fingers crossed 🤞 once again congrats!

@jeremydmiller, I’d also vote for a dedicated page. I’m not sure if it has to be named CQRS. To not make some people defensive, maybe “Handling Business Logic” would be better and then inside mention CQRS.

Babu Annamalai

@mysticmind

@jeremydmiller if we have it in a separate page, discovery is going to be a problem since it is not cohesively in one place. I would suggest to add to to appending itself. Thoughts?

Just re-looking, alternative is to put it in https://martendb.io/scenarios/aggregates-events-repositories.html where we are talking about different scenarios. So this could be in a scenario based explanation.

in addition, put it under appending as well for each method. Also a a link to a section in the above mentioned page with a short explanation.

Probably, the above is better...

Phillip Haydon

@phillip-haydon

repositories bad!

Babu Annamalai

@mysticmind

I meant to add a scenarios page for using FetchForWriting()

Babu Annamalai

@mysticmind

@jeremydmiller PR's JasperFx/marten#2322 (merged recently) and JasperFx/marten#2310 look to be related. Possibly, we can close #2310 as well?

Simon Lovely

@slovely

Hi all, I've watched the great videos last week by Jeremy and Oskar, and had a quick play with the event sourcing stuff. I'm missing something fundamental in how projections work though, and wonder if anyone would be able to spare 10 mins to tell me what I'm doing wrong. I think everything needed to repro is here: https://gist.github.com/slovely/ee50e8ffb318d604473ed66c585d17b5
Basically, I've created a couple of events and have a SelfAggregating projection, but only the most recent event seems to be reflected in the projection. See the comment on the gist for the full repro steps. My understanding could be wrong, but I thought that the projection would contain the latest state of all the events.
Thanks very much,
Simon

Jeremy D. Miller

@jeremydmiller

@mysticmind Yeah, I didn’t notice that the PR came in with the fix before I dealt with that. The fix I did is more generic and should go forward. I thought we could take in his test code as another regression at least. I just didn’t get around to doing the merging yet

1 reply

Oskar Dudycz

@oskardudycz

Hey Simon, I apologise for the delay in answering you on Twitter; I’ll try to do that later today.

Jeremy D. Miller

@jeremydmiller

@slovely You’re wiping the data in the database between tests is the first thing: https://gist.github.com/slovely/ee50e8ffb318d604473ed66c585d17b5#file-marteneventstoretests-cs-L33

Simon Lovely

@slovely

No worries Oskar - it's free help, you are under no obligation :)
@jeremydmiller I'm not re-running that test though, just running specific ones.

But I could definitely be doing something wrong!

Jeremy D. Miller

@jeremydmiller

@slovely Can you be a little more specific about what is not working? A failing test would be best. You’re not doing anything that isn’t straight forward

Simon Lovely

@slovely

Sure, let me try and amalgamate that all into a single test. It's definitely going to be me doing something wrong :)

Simon Lovely

@slovely

@jeremydmiller @oskardudycz OK doing that has lead me to discovering the issue! (should have explained it to a rubber duck first!). The problem is resolved if I change the properties on the projection to not have a private setter. I shouldn't have assumed that Marten would use reflection!

Oskar Dudycz

@oskardudycz

Thanks for follow up 👍 Check also https://martendb.io/configuration/json.html

You can set the private members handling options also to allow private ones.

The important thing is I have a field named Id with getter and setter

See also https://martendb.io/documents/identity.html about identities

Simon Lovely

@slovely

Thanks - using _.UseDefaultSerialization(nonPublicMembersStorage: NonPublicMembersStorage.NonPublicSetters); also fixes it (as did init properties too). All makes perfect sense, knew it would be something straightforward!

Appreciate the help guys!

Oskar Dudycz

@oskardudycz

Happy to help 👍

Michał Gajek

@migajek

Hello :) I have a question regarding projections. Is there any guarantee on the order of projections processing (especially when rebuilding)?
Since built-in projections can take IQuerySession for doing additional lookups, I wonder if it is feasible to query against documents generated by other projections? But for that, we'd need to have some guarantees on the order of processing.
Alternatives I can think of, are keeping "helper" documents or doing live aggregations for lookups

Oskar Dudycz

@oskardudycz

Nope, there's no guarantee about ordering between projections.

Typically, it's best to avoid having dependencies between projections for that reasons.

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