mathroule/room-delete-entity-sample

Room delete entity sample

Sample project to showcase Room not deleting table when an entity is deleted during destructive migration.

To test the project, run master branch on a device. Then checkout one of the following branch and run it on the same device.

Delete an entity

Branch delete-book-entity: Book entity has been removed from code. The User entity columns has been removed. Room will not drop the table during the database destructive migration, it will lead to invalid foreign key constraint, since referenced column has been removed.

Database schema version 1

Database schema version 2

Convert an entity to a database view

Branch convert-book-entity-to-view: Book entity has been transformed to a database view. Room will not drop the table during the database destructive migration, but will try to delete the view. This lead to crash:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mathroule.sample.room/com.mathroule.sample.room.MainActivity}: android.database.sqlite.SQLiteException: use DROP TABLE to delete table book (code 1 SQLITE_ERROR): , while compiling: DROP VIEW IF EXISTS `book`
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:193)
    at android.app.ActivityThread.main(ActivityThread.java:6669)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
 Caused by: android.database.sqlite.SQLiteException: use DROP TABLE to delete table book (code 1 SQLITE_ERROR): , while compiling: DROP VIEW IF EXISTS `book`
    at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
    at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:903)
    at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:514)
    at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
    at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
    at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1769)
    at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1698)
    at androidx.sqlite.db.framework.FrameworkSQLiteDatabase.execSQL(FrameworkSQLiteDatabase.java:242)
    at com.mathroule.sample.room.database.SampleDatabase_Impl$1.dropAllTables(SampleDatabase_Impl.java:44)
    at androidx.room.RoomOpenHelper.onUpgrade(RoomOpenHelper.java:114)
    at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.onUpgrade(FrameworkSQLiteOpenHelper.java:124)
    at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:398)
    at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:298)
    at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper$OpenHelper.getWritableSupportDatabase(FrameworkSQLiteOpenHelper.java:92)
    at androidx.sqlite.db.framework.FrameworkSQLiteOpenHelper.getWritableDatabase(FrameworkSQLiteOpenHelper.java:53)
    at androidx.room.RoomDatabase.inTransaction(RoomDatabase.java:476)
    at androidx.room.RoomDatabase.assertNotSuspendingTransaction(RoomDatabase.java:281)
    at com.mathroule.sample.room.database.SampleDao_Impl.insert(SampleDao_Impl.java:39)
    at com.mathroule.sample.room.MainActivity.onCreate(MainActivity.kt:19)
    at android.app.Activity.performCreate(Activity.java:7136)
    at android.app.Activity.performCreate(Activity.java:7127)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048) 
    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808) 
    at android.os.Handler.dispatchMessage(Handler.java:106) 
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:6669) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Generated sample database implementation

Version 1	Removed Book entity	Converted Book entity to view