hi all đź‘‹ going through the docs I noticed Marten doesn't support
Intersect Linq operator. Is there any alternative way to achieve this functionality? I'm trying to check if two arrays intersect in Marten query.
4 replies
@/all I started to work on the Marten API for Upcasting events data. I'd like to add a built-in tooling for simple payload transformations. You could use that if your event schema has changed and you'd like to use new event types in your aggregates and projections. Those transformations will be run during the serialisation phase, so upcasting on the fly old event data into the new one.
I added two types of upcasters:
- CLR types - when you're fine with keeping old event payload then it'll at first deserialise it, and you can map to the new one,
- Raw json transformations, more flexible, less allocation, but a bit more tedious.
I have an early draft, of it, I'd be grateful for your feedback, especially about the public API (e.g. accessibility, naming, etc.).
Technically, this is what I described in my blog article: https://event-driven.io/en/simple_events_versioning_patterns/
Thoughts?
https://twitter.com/oskar_at_net/status/1555854977700184064 - would be greateful for RT to get more feedback :)
That's all Postgresql & Npgsql. Start here maybe: https://www.npgsql.org/doc/security.html?tabs=tabid-1
I have a question regarding the Marten Linq Provider. How come it can understand a query such as querySession.Query<Book>().Where(b => true).ToList();
But can not understand a query such as querySession.Query<Book>().Where(b => b != null).ToList();
In the end, these queries don't really filter anything out , but I'm curious to know why the first one is executed successfully where the second one keeps triggering an exception.
But can not understand a query such as querySession.Query<Book>().Where(b => b != null).ToList();
In the end, these queries don't really filter anything out , but I'm curious to know why the first one is executed successfully where the second one keeps triggering an exception.
Okay, so the Linq provider never executes your code, rather it's an interpreter. Meaning that we have to anticipate and in many cases explicitly code for every single possible usage in order for that to work. The well lit paths are going to be fine. Oddball things that we didn't anticipate anybody every using like
Where(x => x == null), are probably not going to have explicit support.
So the next question is, why in the world would you possibly do that?
Good question. I'm not wrtiting these queries manually myself. I'm currently trying to integrate the HotChocolate GraphQl library with Marten. It comes with out of the box support with some nice features like liftering (https://chillicream.com/docs/hotchocolate/fetching-data/filtering), which works by converting the graphql arguments into an expression tree that it then will apply to the IMartenQueryable. Let's say I have a Book object which as a Rating property. If I want to filter by that property, It will generate an expression that looks like $_s0 != null && $_s0.Rating == 10 instead of just $_s0.Rating == 10. That first part of the expression is what is causing the problem.
And that's such a horrendously inefficient way to do that
Gotta go, I'll be back. You submitted an issue for this anyway, righ?
Is it reasonable to set a UserId Header on any session like this? Do people something similar or is putting a user id on metadata not something you usually want to do?
public class ScopedSessionFactory: ISessionFactory
{
private readonly IDocumentStore store;
private readonly IUserService userService;
public ScopedSessionFactory(IDocumentStore store, IUserService userService)
{
this.store = store;
this.userService = userService;
}
public IQuerySession QuerySession()
{
return store.QuerySession();
}
public IDocumentSession OpenSession()
{
var session = store.LightweightSession();
var userId = userService.GetUserId();
session.SetHeader("UserId", userId);
return session;
}
}Are these diagnostic messages normal/expected? I get them several times per second
`
[14:31:51 INF] High Water agent is stale after threshold of 3 seconds, skipping gap to events marked after 08/08/2022 12:30:20 +00:00
[14:31:51 INF] Daemon projection high water detection skipping a gap in event sequence, determined that the 'safe harbor' sequence is at null
`
You can bump up that “stale time” if you have long running transactions in your system that make it look like it’s stale
Marten should be putting tombstone events in place of the failed events, but maybe we've never tested that workflow in the case of serialization failures earlier in the SaveChanges() call.
Im using System.text.json + https://github.com/Tarmil/FSharp.SystemTextJson and I actually like it. It gives some errors as kind of expected but actually now I have a model that I am happy with. I.e. strings are now not nullable but need to be "string option" (FsharpOption) and null will error on de/serializing
To balance that, F# user experience will be my next goal after merging Upcasters PR. If you could write up all of your challenges in the GH issue, then I could try to include that.
Still, I need to learn F# language and idiomatic approach better, so it’ll take some time
It's not something that always happens and I haven't been able to reliably recreate it, but ive taken to putting an extra ToString on all my header calls
JObject could be returned if there was an unknown type and it did dynamic deserialisation. It can be cast to the specific type.
Tested with Newtonsoft and fsharp types are serialized okish, however the deserialization format for options and discriminated unions is imho not ideal. For both types are different json representations possible, Ill try write a blogpost about my experiences but not yet sure when...
Do you think that being able to do custom serialization like in my PR would help? JasperFx/marten#2314
1 reply
In theory, it’s more for event schema migration, but I was thinking of making it more generic also for documents as the next step
What is the default for
AutoCreateSchemaObjects if it's not specified? I have queries periodically failing for a service running in Google Cloud Run with timeouts like so. Just wondering what could be the reason.---> System.TimeoutException: The operation has timed out.
at Weasel.Core.Migrations.TimedLock.Lock(TimeSpan timeout)
at Weasel.Core.Migrations.DatabaseBase`1.generateOrUpdateFeature(Type featureType, IFeatureSchema feature, CancellationToken token)
at Weasel.Core.Migrations.DatabaseBase`1.ensureStorageExists(IList`1 types, Type featureType, CancellationToken token)
at Marten.Linq.MartenLinqQueryProvider.ensureStorageExistsAsync(LinqHandlerBuilder builder, CancellationToken cancellationToken)
at Marten.Linq.MartenLinqQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken token)
My assumption is that the default is
None, but why is it then trying to apply migrations
Looking at the sauce the default appears to be
CreateOrUpdate ouch
@EgorPavlikhin_twitter It's
CreateOrUpdate to enable quick developer starts. Check out this topic maybe: https://martendb.io/configuration/optimized_artifact_workflow.html