Android Room Persistence Library: Upsert

Question

Android\'s Room persistence library graciously includes the @Insert and @Update annotations that work for objects or collections. I however have a use case (push notificatio

Answer 1

Just an update for how to do this with Kotlin retaining data of the model (Maybe to use it in a counter as in example):

//Your Dao must be an abstract class instead of an interface (optional database constructor variable)
@Dao
abstract class ModelDao(val database: AppDatabase) {

@Insert(onConflict = OnConflictStrategy.FAIL)
abstract fun insertModel(model: Model)

//Do a custom update retaining previous data of the model 
//(I use constants for tables and column names)
 @Query("UPDATE $MODEL_TABLE SET $COUNT=$COUNT+1 WHERE $ID = :modelId")
 abstract fun updateModel(modelId: Long)

//Declare your upsert function open
open fun upsert(model: Model) {
    try {
       insertModel(model)
    }catch (exception: SQLiteConstraintException) {
        updateModel(model.id)
    }
}
}

You can also use @Transaction and database constructor variable for more complex transactions using database.openHelper.writableDatabase.execSQL("SQL STATEMENT")