I'm trying to create a backup of my sqlite database and I want to flush the content of the WAL file in the db first.
Here is my SQLiteOpenHelper:
public class MyDBHelper extends SQLiteOpenHelper {
private Context mContext;
private static MyDBHelper mInstance = null;
private MyDBHelper(final Context context, String databaseName) {
super(new MYDB(context), databaseName, null, DATABASE_VERSION);
this.mContext = context;
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
public static MyDBHelper getInstance(Context context) {
if (mInstance == null) {
mInstance = new MyDBHelper(context, DATABASE_NAME);
}
return mInstance;
}
private void closeDataBase(Context context) {
getInstance(context).close();
}
}
Now, my understanding is that after a checkpoint is completed, the mydb.db-wal file should be empty. Is that correct?
Here is what I've tried so far: 1.
public Completable flushWalInDB() {
return Completable.fromAction(new Action() {
@Override
public void run() throws Exception {
getInstance(mContext).getReadableDatabase().rawQuery("pragma wal_checkpoint;", null);
}
});
}
This doesn't throw an error but doesn't seem to do anything. After running this, I physically checked my mydb.db-wal file and had the same size. I also checked the db on the device and nothing was added in the database
After some digging around I found this [https://stackoverflow.com/a/30278485/2610933][1] and tried this:
2.
public Completable flushWalInDB() {
return Completable.fromAction(new Action() {
@Override
public void run() throws Exception {
getInstance(mContext).getReadableDatabase().execSQL("pragma wal_checkpoint;");
}
});
}
When running this it throws an error:
unknown error (code 0): Queries can be performed using SQLiteDatabase query or rawQuery methods only.
And based on this answer [https://stackoverflow.com/a/19574341/2610933][1] , I also tried to VACUUM the DB but nothing seems to happen.
public Completable vacuumDb() {
return Completable.fromAction(new Action() {
@Override
public void run() throws Exception {
getInstance(mContext).getReadableDatabase().execSQL("VACUUM");
}
});
}
}
Whats is the correct way of flushing the WAL file in the DB before creating a backup?
Thank you.
