The original question is at the very bottom. I have created a minimal (non-)working example of my problem which is hopefully easier to read through. The example is here at gitlab. There is a readme describing the problem. I am pasting some parts of the project here.
The data model is plain simple:
Owner <--(1:N)-- Child --(N:1)--> ReferencedByChild
All I want to do is to read an Owner from the database with all its associated Child objects and for each Child object
also the ReferencedByChild object that it references.
The whole code that reproduces my problem is below. What I am not 100% sure about is the @Relation on the OwnerWithEverything POJO. See below please.
@Database(
entities = [
Owner::class,
Child::class,
ReferencedByChild::class
],
version = 1
)
abstract class AppDatabase : RoomDatabase() {
abstract fun appDao(): AppDao
}
@Dao
abstract class AppDao {
@Insert
abstract fun insertOwner(owner: Owner): Long
@Insert
abstract fun insertChild(child: Child): Long
@Insert
abstract fun insertReferencedByChild(referencedByChild: ReferencedByChild): Long
@Query("SELECT * FROM Child INNER JOIN ReferencedByChild ON Child.referencedByChildId = ReferencedByChild.refByChildId ORDER BY Child.childText")
abstract fun findAllChildrenWithReferencedClasses(): List<ChildWithReferenced>
// Commenting this query out makes the build pass, so something here is incorrect.
@Query("SELECT * FROM Owner")
abstract fun findOwnersWithEverything(): List<OwnerWithEverything>
}
// ENTITIES
@Entity
data class Owner(
@PrimaryKey(autoGenerate = true)
val ownerId: Long,
val ownerText: String
)
@Entity(
foreignKeys = [
ForeignKey(
entity = Owner::class,
parentColumns = arrayOf("ownerId"),
childColumns = arrayOf("referencedOwnerId"),
onDelete = ForeignKey.CASCADE
),
ForeignKey(
entity = ReferencedByChild::class,
parentColumns = arrayOf("refByChildId"),
childColumns = arrayOf("referencedByChildId"),
onDelete = ForeignKey.CASCADE
)
]
)
data class Child(
@PrimaryKey(autoGenerate = true)
val childId: Long,
val childText: String,
val referencedOwnerId: Long,
val referencedByChildId: Long
)
@Entity
data class ReferencedByChild(
@PrimaryKey(autoGenerate = true)
val refByChildId: Long,
val refText: String
)
// POJOS
// The Child has exactly one ReferencedByChild reference. This POJO joins those two
class ChildWithReferenced(
@Embedded
var child: Child,
@Embedded
var referencedByChild: ReferencedByChild
)
class OwnerWithEverything {
@Embedded
var owner: Owner? = null
@Relation(
parentColumn = "ownerId",
entityColumn = "referencedOwnerId",
entity = Child::class // which entity should be defined here?
)
var childrenWithReferenced: List<ChildWithReferenced>? = null
}
Building this code results in this error message:
error: There is a problem with the query: [SQLITE_ERROR] SQL error or missing database (no such column: refByChildId)
I think that the Owner query is badly constructed, but I am not entirely sure. If that is the problem, what is the correct way to construct the query?
This is the original question
I have a nested POJO structure that should represent a single Game having multiple Rounds and each Round has a single Topic associated with it:
class GameWithRounds {
@Embedded
var game: Game? = null
@Relation(
parentColumn = "id",
entityColumn = "gameId",
entity = RoundRoom::class
)
var rounds: List<RoundWithTopic>? = null
}
class RoundWithTopic(
@Embedded
var round: RoundRoom,
@Embedded(prefix = "topic_")
var topic: Topic
)
The embedded annotation on Topic specifies a prefix because there are clashing id properties.
The Room Query that can fetch those classes is:
@Query("SELECT Topic.id as topic_id, Topic.name as topic_name, (...), RoundRoom.* FROM RoundRoom INNER JOIN Topic ON RoundRoom.topicId = Topic.id")
abstract fun findRoundsWithTopics(): List<RoundWithTopic>
However, building the project gives me Room errors:
There is a problem with the query: [SQLITE_ERROR] SQL error or missing database (no such column: topic_id)
Even though when I induce a warning about which fields are actually present, this is what Room tells me:
Columns returned by the query: topic_id, topic_name, topic_description, topic_language, topic_keywords, topic_sourceUrls, topic_furtherUrls, topic_questions, order, gameId, topicId, status, id. Fields in cz.melkamar.sklapecka.model.RoundWithTopic: order, gameId, topicId, status, id, topic_id, topic_name, topic_description, topic_language, topic_keywords, topic_sourceUrls, topic_furtherUrls, topic_questions, topic_image.
The topic_id column is there in the query result! Why am I getting this error?
For completeness, this is the entities:
@Entity
data class Game(
@PrimaryKey(autoGenerate = true)
val id: Long = 0,
@Embedded
val gameConfigurationEmbed: GameConfigurationEmbed
)
data class GameConfigurationEmbed(
var secondsPerTurn: Int,
var maxSecondsPerTurn: Int,
var bonusSecondsPerAnswer: Int
)
@Entity(
foreignKeys = [
ForeignKey(
entity = Game::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("gameId"),
onDelete = ForeignKey.CASCADE
),
ForeignKey(
entity = Topic::class,
parentColumns = arrayOf("id"),
childColumns = arrayOf("topicId"),
onDelete = ForeignKey.CASCADE
)
]
)
@TypeConverters(RoomConverters::class)
data class RoundRoom(
val order: Int,
var gameId: Long,
val topicId: String,
var status: RoundStatus = RoundStatus.CREATED,
@PrimaryKey(autoGenerate = true)
val id: Long = 0
) {
enum class RoundStatus {
CREATED, UPCOMING, IN_PROGRESS, FINISHED
}
}
@Entity
data class Topic(
@PrimaryKey val id: String,
val name: String,
val description: String,
val language: String,
val keywords: List<String>,
val sourceUrls: List<String>,
val furtherUrls: List<String>,
val questions: List<String>,
val image: ByteArray?
)
