ebean-orm
Chained fetch() calls
Hello,
I ran into an issue where if I have an entity that has multiple @OneToMany relations, and I attempt to fetch all of them, i.e.
QPerson().fetch("cars", "*").fetch("pets", "*").where().lastName.ieq("somedude").findOne()
only the first fetch gets executed, and the following (one or more fetches) is ineffective and produces no error.
I isolated the issue from my project in a standalone repo for convenience: https://github.com/martinkala1/ebean-chained-fetch
Note, that I do not have a lot of experience working with ebean, so You may find places where the example is not up to standard, for which I apologize.
My understanding is, that this operation should successfully fetch all the related entities, or at least produce some error/warning. Is this intended behavior or am I perhaps missing something?
Thanks for Your time, Martin
Hello @martinkala1,
Ebean has several fetch strategies: https://ebean.io/docs/query/fetch
in general, ebean can only fetch one many-relation in one query. In your example it will buld select * from person left join cars ... which results in person x cars rows. If you will also join pets, the result may "explode"
Normally additional manys are loaded batch wise. You may try an explicit "fetchQuery" here. (although the docs say, that fetch is converted automatically to fetchQuery. But I'm unsure if this is correct or if this means, that everything is fetched at once)
If the OneToMany collections are moved out of the constructor then it works.
I'm not sure why until I look closer. I'm not sure if this is kotlin specific yet.
On Tue, 17 Jun 2025, 5:40 am Roland Praml, @.***> wrote:
rPraml left a comment (ebean-orm/ebean#3642) https://github.com/ebean-orm/ebean/issues/3642#issuecomment-2977477874
Hello @martinkala1 https://github.com/martinkala1,
Ebean has several fetch strategies: https://ebean.io/docs/query/fetch
in general, ebean can only fetch one many-relation in one query. In your example it will buld select * from person left join cars ... which results in person x cars rows. If you will also join pets, the result may "explode"
Normally additional manys are loaded batch wise. You may try an explicit "fetchQuery" here. (although the docs say, that fetch is converted automatically to fetchQuery. But I'm unsure if this is correct or if this means, that everything is fetched at once)
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Hello, https://github.com/ebean-orm/ebean/issues/3642#issuecomment-2979323949 fixes it, thanks!