How can I delete all entries on specific table using Room Persistence Library? I need to drop table, but I cannot to find any information how to do this.
Only when database is migrating or to load all entries and delete them :)
This question is related to
android
android-room
android-architecture-components
You can create a DAO method to do this.
@Dao
interface MyDao {
@Query("DELETE FROM myTableName")
public void nukeTable();
}
As of Room 1.1.0
you can use clearAllTables() which:
Deletes all rows from all the tables that are registered to this database as entities().
Use clearAllTables() with RXJava like below inorder to avoid java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
Completable.fromAction(new Action() {
@Override
public void run() throws Exception {
getRoomDatabase().clearAllTables();
}
}).subscribeOn(getSchedulerProvider().io())
.observeOn(getSchedulerProvider().ui())
.subscribe(new Action() {
@Override
public void run() throws Exception {
Log.d(TAG, "--- clearAllTables(): run() ---");
getInteractor().setUserAsLoggedOut();
getMvpView().openLoginActivity();
}
}, new Consumer<Throwable>() {
@Override
public void accept(Throwable throwable) throws Exception {
Log.d(TAG, "--- clearAllTables(): accept(Throwable throwable) ----");
Log.d(TAG, "throwable.getMessage(): "+throwable.getMessage());
}
});
If want to delete an entry from the the table in Room simply call this function,
@Dao
public interface myDao{
@Delete
void delete(MyModel model);
}
Update: And if you want to delete complete table, call below function,
@Query("DELETE FROM MyModel")
void delete();
Note: Here MyModel is a Table Name.
To make use of the Room without abuse of the @Query
annotation first use @Query
to select all rows and put them in a list, for example:
@Query("SELECT * FROM your_class_table")
List`<`your_class`>` load_all_your_class();
Put his list into the delete annotation, for example:
@Delete
void deleteAllOfYourTable(List`<`your_class`>` your_class_list);
This is how we do it.
fun Fragment.emptyDatabase() {
viewLifecycleOwner.lifecycleScope.launchWhenCreated {
withContext(Dispatchers.IO) {
Database.getInstance(requireActivity()).clearAllTables()
}
}
}
Here is how I have done it in Kotlin.
Inject room db in the activity using DI (Koin).
private val appDB: AppDB by inject()
Then you can simply call clearAllTables()
private fun clearRoomDB() {
GlobalScope.launch {
appDB.clearAllTables()
preferences.put(PreferenceConstants.IS_UPLOADCATEGORIES_SAVED_TO_DB, false)
preferences.put(PreferenceConstants.IS_MEMBERHANDBOOK_SAVED_TO_DB, false)
}
}
I had issues with delete all method when using RxJava to execute this task on background. This is how I finally solved it:
@Dao
interface UserDao {
@Query("DELETE FROM User")
fun deleteAll()
}
and
fun deleteAllUsers() {
return Maybe.fromAction(userDao::deleteAll)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe ({
d("database rows cleared: $it")
}, {
e(it)
}).addTo(compositeDisposable)
}
Combining what Dick Lucas says and adding a reset autoincremental from other StackOverFlow posts, i think this can work:
fun clearAndResetAllTables(): Boolean {
val db = db ?: return false
// reset all auto-incrementalValues
val query = SimpleSQLiteQuery("DELETE FROM sqlite_sequence")
db.beginTransaction()
return try {
db.clearAllTables()
db.query(query)
db.setTransactionSuccessful()
true
} catch (e: Exception){
false
} finally {
db.endTransaction()
}
}
Source: Stackoverflow.com