room-patterns

Room Database Patterns

Dependencies (build.gradle.kts)

plugins {
    id("com.google.devtools.ksp") version "2.3.10"
    id("androidx.room") version "2.8.4" // Room Gradle plugin: schema location + auto-migration wiring
}

room {
    schemaDirectory("$projectDir/schemas")
}

dependencies {
    val roomVersion = "2.8.4"
    implementation("androidx.room:room-runtime:$roomVersion")
    ksp("androidx.room:room-compiler:$roomVersion")
    testImplementation("androidx.room:room-testing:$roomVersion")
}

Artifacts. room-ktx was merged into room-runtime in 2.7.0 — the artifact is now empty, remove it. room-testing, room-paging, room-rxjava3, room-guava remain separate.

Room 2.x vs Room 3

Room 3.0 is stable (3.0.1, July 2026) under new coordinates: androidx.room3:room3-runtime / room3-compiler, Gradle plugin id androidx.room3 with a room3 { schemaDirectory(...) } extension, package androidx.room3. androidx.room 2.8.x is in maintenance mode — bug-fix patches only, no new features. Stay on 2.8.x for an existing Android-only codebase; start new code, and anything heading to KMP, on androidx.room3.

Room 3 differences that break the snippets below:

• Kotlin-only codegen, KSP-only — no KAPT, no Java annotation processing.
• Coroutines-first: every non-reactive DAO function must be suspend; blocking DAO functions are rejected at compile time.
• SupportSQLite is gone in favor of the androidx.sqlite driver API. Migration.migrate(db: SupportSQLiteDatabase) becomes abstract suspend fun migrate(connection: SQLiteConnection), and openHelper.writableDatabase becomes roomDatabase.getSupportWrapper() from the room3-sqlite-wrapper bridge artifact.
• Non-scalar DAO return types are opt-in: register the converter class with @DaoReturnTypeConverters(...) on the @Dao or @Database (@DaoReturnTypeConverter annotates the converter function itself). PagingSource needs @DaoReturnTypeConverters(PagingSourceDaoReturnTypeConverter::class) from room3-paging; LiveData needs LiveDataDaoReturnTypeConverter from room3-livedata. Without it KSP fails with "Not sure how to convert the query result to this function's return type".