I’m using the DAO and I have an object with a one-to-many relationship. How can I load the list when...

# exposed

[pindab0ter]

I’m using the DAO and I have an object with a one-to-many relationship. How can I load the list when I load that object? And if that’s not possible, when is it better to do more things within the transaction context or to open/close multiple transactions within short succession of each other?

[tapac]

parentEntity.children.toList() ?

[tapac]

Or https://github.com/JetBrains/Exposed/wiki/DAO#eager-loading

[pindab0ter]

I’m still getting No transaction in context errors when using the eager loading.

[tapac]

Could you share a piece of a code?

[pindab0ter]

The toList() solution works, but weird, since I now have a separate list of children that are now separate from their parent

[tapac]

You just ask for it How can I load the list when I load that object? 😄

[pindab0ter]

True, but that list is (supposed to be) part of that object 😉

[pindab0ter]

val discordUser: DiscordUser? = transaction {
    DiscordUser.find { DiscordUsers.discordTag like "$name%" }.firstOrNull()?.load(DiscordUser::farmers)
}

[pindab0ter]

This seems like it should work, but this gives me the No transaction in context error when I try to access .farmers outside of a transaction.

[tapac]

Sad, but all references are transaction-bound, so you can't call for it our of transaction block.

[pindab0ter]

Alright, then I misunderstood what eager loading was about 🙂

[tapac]

It's an approach to prevent N+1 problem on loading multiple entities and their relations

[pindab0ter]

I’m not familiar with that problem, but I can think of what that could mean. Thank you for your time and explanation. I’ll stick to using the .toList() method 🙂