Room multimap LEFT JOIN nullability [201946438]

Fixed

Bug

Status Update

No update yet.

Description

aa...@gmail.com

created issue #1

Oct 4, 2021 02:36PM

Artifact used : Room Version used: 2.4.0-alpha05 Devices/Android versions reproduced on: Emulator

This is more of a feature request, but trying out the new multimap feature I'm having issues with LEFT JOIN queries.

Take this example from the release notes (One-to-Many relationship):

@Query("SELECT * FROM Artist JOIN Album ON Artist.id = Album.artistId")
fun getArtistAndAlbums(): Map<Artist, List<Album>>

Let's say we want all artists, regardless if they have any albums. So we change the query to use a LEFT JOIN:

@Query("SELECT * FROM Artist LEFT JOIN Album ON Artist.id = Album.artistId")
fun getArtistAndAlbums(): Map<Artist, List<Album>>

This won't work if we have an Artist without albums, if Album doesn't have any nullable fields. Because the current implementation will always try and generate an Album object.

Is it possible to let Room return an empty list of 'Albums' in that case? Or Map<Artist, List<Album>?>?

Thanks for your time!

Comments

au...@google.com <au...@google.com> Oct 6, 2021 08:29PM

Assigned to da...@google.com.

el...@google.com <el...@google.com> #2Oct 6, 2021 09:42PM

Reassigned to el...@google.com.

For Kotlin 2.0 and KSP 2.0 the Cannot change attributes of configuration ':composeApp:debugFrameworkIosX64' after it has been locked for mutation really seems like a KSP issue. You should file a bug in their repository with a sample app if possible.

If you downgrade to Kotlin 1.9 then things 'should' work, there are example apps out there with such configuration, like the following one: https://github.com/realityexpander/KMP_Room/tree/main

aa...@gmail.com <aa...@gmail.com> #3Oct 11, 2021 10:56AM

Yes this does seem like a KSP issue however it only starts happening when room is added to the project. As the template project compiles just fine.

Will try to use the example provided by you to check if it fixes the issue.

el...@google.com <el...@google.com> Nov 4, 2021 12:12AM

Marked as fixed.

ap...@google.com <ap...@google.com> #4Nov 4, 2021 12:13AM

Note that this issue happens when applying the Compose, KSP and Room Plugin together in Kotlin 2.0.x, the workaround for now is to not use the Room Gradle Plugin and instead specify the schema location vis KSP arguments:

// In the build.gradle
ksp {
    arg("room.schemaLocation", "${projectDir}/schemas")
}

mr...@crossway.org <mr...@crossway.org> #5Dec 2, 2021 08:50PM

Hi, I encountered a similar problem and was able to resolve it by updating the dependencies

room = "2.7.0-alpha08"
ksp = "2.0.20-1.0.25"

compose-plugin = "1.6.11"
kotlin = "2.0.20"

mr...@crossway.org <mr...@crossway.org> #6Dec 2, 2021 09:51PM

Ah sorry, bad report. After looking at the generated file a bit closer I realized that the problem was a slightly different one. I will file a separate bug report.