多房间迁移导致android报错

Question

I need to migrate the Database version 5 to 6, 6 to 7 and vice versa.

So what I did is.

Room.databaseBuilder(context, MainDatabase::class.java, DB_NAME)
    .addMigrations(
        MIGRATION_7_6,
        MIGRATION_6_5,
        MIGRATION_5_6,
        MIGRATION_6_7)
    .build()

The migration between 5 and 6 was fine. And now I am implementing between 6 and 7.

Here's MIGRATIONs

val MIGRATION_6_7 = object : Migration(6, 7) {
    override fun migrate(database: SupportSQLiteDatabase) {
        database.execSQL("CREATE TABLE ResultConfig(seq INTEGER NOT NULL, json_data TEXT NOT NULL, updated_at TEXT NOT NULL, created_at TEXT NOT NULL, PRIMARY KEY(seq))")
    }
}

val MIGRATION_7_6 = object : Migration(7, 6) {
    override fun migrate(database: SupportSQLiteDatabase) {
        database.execSQL("DROP TABLE ResultConfig")
    }
}

@Parcelize
@Keep
@Entity(tableName = "result_config")
data class ResultConfig(
        @PrimaryKey(autoGenerate = true) val seq: Long,
        @ColumnInfo(name = "json_data") var jsonData: String,
        @ColumnInfo(name = "updated_at") var updatedAt: String,
        @ColumnInfo(name = "created_at") var createdAt: String
) : Parcelable {
}

And here's the error.

Expected:
    TableInfo{name='result_config', columns={created_at=Column{name='created_at', type='TEXT',
affinity='2', notNull=true, primaryKeyPosition=0,
defaultValue='null'}, updated_at=Column{name='updated_at',
type='TEXT', affinity='2', notNull=true, primaryKeyPosition=0,
defaultValue='null'}, seq=Column{name='seq', type='INTEGER',
affinity='3', notNull=true, primaryKeyPosition=1,
defaultValue='null'}, json_data=Column{name='json_data', type='TEXT',
affinity='2', notNull=true, primaryKeyPosition=0,
defaultValue='null'}}, foreignKeys=[], indices=[]}
Found:
    TableInfo{name='result_config', columns={}, foreignKeys=[], indices=[]}

I think the table hasn't created properly.

But the database class is like this:

@Database(entities = [A::class, B::class, ResultConfig::class], version = 7, exportSchema = false)
abstract class MainDatabase : RoomDatabase() {
    // TODO:
}

So, the current version is 7. And older version is 6.

What's the problem?

UPDATE

I found the problem and it causes because of MIGRATION_6_7. This line.

database.execSQL("CREATE TABLE ResultConfig(seq INTEGER NOT NULL, json_data TEXT NOT NULL, updated_at TEXT NOT NULL, created_at TEXT NOT NULL, PRIMARY KEY(seq))")

However, when I try this line, it worked.

database.execSQL("CREATE TABLE `remote_config`(seq INTEGER NOT NULL, json_data TEXT NOT NULL, updated_at TEXT NOT NULL, created_at TEXT NOT NULL, PRIMARY KEY(seq))")

But I really want to use the annotation - @Entity(tableName = "result_config") in the Entity class for integrity. How can I solve and achieve it?

Answer 1

Hum... your code is weird. You don't need to provide a 'downgrade migration' because you must always increase the DB version. Instead, in case of downgrade, it's better to flush the DB with the fallback method

Room.databaseBuilder(context, MainDatabase::class.java, DB_NAME)
    .addMigrations(
        MIGRATION_5_6,
        MIGRATION_6_7)
    .fallbackToDestructiveMigrationOnDowngrade()
    .build()