gt: 		db.delete(Account.TABLENAME, Account.UUID + "=?", args);
context: package eu.siacs.conversations.persistance;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;
  
  import eu.siacs.conversations.entities.Account;
  import eu.siacs.conversations.entities.Contact;
  import eu.siacs.conversations.entities.Conversation;
  import eu.siacs.conversations.entities.Message;
  import eu.siacs.conversations.entities.Roster;
  import eu.siacs.conversations.xmpp.jid.Jid;
  
  import android.content.Context;
  import android.database.Cursor;
  import android.database.sqlite.SQLiteCantOpenDatabaseException;
  import android.database.sqlite.SQLiteDatabase;
  import android.database.sqlite.SQLiteOpenHelper;
  
  public class DatabaseBackend extends SQLiteOpenHelper {
  
  	private static DatabaseBackend instance = null;
  
  	private static final String DATABASE_NAME = "history";
  	private static final int DATABASE_VERSION = 13;
  
  	private static String CREATE_CONTATCS_STATEMENT = "create table "
  			+ Contact.TABLENAME + "(" + Contact.ACCOUNT + " TEXT, "
  			+ Contact.SERVERNAME + " TEXT, " + Contact.SYSTEMNAME + " TEXT,"
  			+ Contact.JID + " TEXT," + Contact.KEYS + " TEXT,"
  			+ Contact.PHOTOURI + " TEXT," + Contact.OPTIONS + " NUMBER,"
  			+ Contact.SYSTEMACCOUNT + " NUMBER, " + Contact.AVATAR + " TEXT, "
              + Contact.LAST_PRESENCE + " TEXT, " + Contact.LAST_TIME + " NUMBER, "
  			+ Contact.GROUPS + " TEXT, FOREIGN KEY(" + Contact.ACCOUNT + ") REFERENCES "
  			+ Account.TABLENAME + "(" + Account.UUID
  			+ ") ON DELETE CASCADE, UNIQUE(" + Contact.ACCOUNT + ", "
  			+ Contact.JID + ") ON CONFLICT REPLACE);";
  
  	private DatabaseBackend(Context context) {
  		super(context, DATABASE_NAME, null, DATABASE_VERSION);
  	}
  
  	@Override
  	public void onCreate(SQLiteDatabase db) {
  		db.execSQL("PRAGMA foreign_keys=ON;");
  		db.execSQL("create table " + Account.TABLENAME + "(" + Account.UUID
  				+ " TEXT PRIMARY KEY," + Account.USERNAME + " TEXT,"
  				+ Account.SERVER + " TEXT," + Account.PASSWORD + " TEXT,"
  				+ Account.ROSTERVERSION + " TEXT," + Account.OPTIONS
  				+ " NUMBER, " + Account.AVATAR + " TEXT, " + Account.KEYS
  				+ " TEXT)");
  		db.execSQL("create table " + Conversation.TABLENAME + " ("
  				+ Conversation.UUID + " TEXT PRIMARY KEY, " + Conversation.NAME
  				+ " TEXT, " + Conversation.CONTACT + " TEXT, "
  				+ Conversation.ACCOUNT + " TEXT, " + Conversation.CONTACTJID
  				+ " TEXT, " + Conversation.CREATED + " NUMBER, "
  				+ Conversation.STATUS + " NUMBER, " + Conversation.MODE
  				+ " NUMBER, " + Conversation.ATTRIBUTES + " TEXT, FOREIGN KEY("
  				+ Conversation.ACCOUNT + ") REFERENCES " + Account.TABLENAME
  				+ "(" + Account.UUID + ") ON DELETE CASCADE);");
  		db.execSQL("create table " + Message.TABLENAME + "( " + Message.UUID
  				+ " TEXT PRIMARY KEY, " + Message.CONVERSATION + " TEXT, "
  				+ Message.TIME_SENT + " NUMBER, " + Message.COUNTERPART
  				+ " TEXT, " + Message.TRUE_COUNTERPART + " TEXT,"
  				+ Message.BODY + " TEXT, " + Message.ENCRYPTION + " NUMBER, "
  				+ Message.STATUS + " NUMBER," + Message.TYPE + " NUMBER, "
  				+ Message.RELATIVE_FILE_PATH + " TEXT, "
  				+ Message.SERVER_MSG_ID + " TEXT, "
  				+ Message.REMOTE_MSG_ID + " TEXT, FOREIGN KEY("
  				+ Message.CONVERSATION + ") REFERENCES "
  				+ Conversation.TABLENAME + "(" + Conversation.UUID
  				+ ") ON DELETE CASCADE);");
  
  		db.execSQL(CREATE_CONTATCS_STATEMENT);
  	}
  
  	@Override
  	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  		if (oldVersion < 2 && newVersion >= 2) {
  			db.execSQL("update " + Account.TABLENAME + " set "
  					+ Account.OPTIONS + " = " + Account.OPTIONS + " | 8");
  		}
  		if (oldVersion < 3 && newVersion >= 3) {
  			db.execSQL("ALTER TABLE " + Message.TABLENAME + " ADD COLUMN "
  					+ Message.TYPE + " NUMBER");
  		}
  		if (oldVersion < 5 && newVersion >= 5) {
  			db.execSQL("DROP TABLE " + Contact.TABLENAME);
  			db.execSQL(CREATE_CONTATCS_STATEMENT);
  			db.execSQL("UPDATE " + Account.TABLENAME + " SET "
  					+ Account.ROSTERVERSION + " = NULL");
  		}
  		if (oldVersion < 6 && newVersion >= 6) {
  			db.execSQL("ALTER TABLE " + Message.TABLENAME + " ADD COLUMN "
  					+ Message.TRUE_COUNTERPART + " TEXT");
  		}
  		if (oldVersion < 7 && newVersion >= 7) {
  			db.execSQL("ALTER TABLE " + Message.TABLENAME + " ADD COLUMN "
  					+ Message.REMOTE_MSG_ID + " TEXT");
  			db.execSQL("ALTER TABLE " + Contact.TABLENAME + " ADD COLUMN "
  					+ Contact.AVATAR + " TEXT");
  			db.execSQL("ALTER TABLE " + Account.TABLENAME + " ADD COLUMN "
  					+ Account.AVATAR + " TEXT");
  		}
  		if (oldVersion < 8 && newVersion >= 8) {
  			db.execSQL("ALTER TABLE " + Conversation.TABLENAME + " ADD COLUMN "
  					+ Conversation.ATTRIBUTES + " TEXT");
  		}
          if (oldVersion < 9 && newVersion >= 9) {
              db.execSQL("ALTER TABLE " + Contact.TABLENAME + " ADD COLUMN "
                      + Contact.LAST_TIME + " NUMBER");
              db.execSQL("ALTER TABLE " + Contact.TABLENAME + " ADD COLUMN "
                      + Contact.LAST_PRESENCE + " TEXT");
          }
  		if (oldVersion < 10 && newVersion >= 10) {
  			db.execSQL("ALTER TABLE " + Message.TABLENAME + " ADD COLUMN "
  					+ Message.RELATIVE_FILE_PATH + " TEXT");
  		}
  		if (oldVersion < 11 && newVersion >= 11) {
  			db.execSQL("ALTER TABLE " + Contact.TABLENAME + " ADD COLUMN "
  					+ Contact.GROUPS + " TEXT");
  			db.execSQL("delete from "+Contact.TABLENAME);
  			db.execSQL("update "+Account.TABLENAME+" set "+Account.ROSTERVERSION+" = NULL");
  		}
  		if (oldVersion < 12 && newVersion >= 12) {
  			db.execSQL("ALTER TABLE " + Message.TABLENAME + " ADD COLUMN "
  					+ Message.SERVER_MSG_ID + " TEXT");
  		}
  		if (oldVersion < 13 && newVersion >= 13) {
  			db.execSQL("delete from "+Contact.TABLENAME);
  			db.execSQL("update "+Account.TABLENAME+" set "+Account.ROSTERVERSION+" = NULL");
  		}
  	}
  
  	public static synchronized DatabaseBackend getInstance(Context context) {
  		if (instance == null) {
  			instance = new DatabaseBackend(context);
  		}
  		return instance;
  	}
  
  	public void createConversation(Conversation conversation) {
  		SQLiteDatabase db = this.getWritableDatabase();
  		db.insert(Conversation.TABLENAME, null, conversation.getContentValues());
  	}
  
  	public void createMessage(Message message) {
  		SQLiteDatabase db = this.getWritableDatabase();
  		db.insert(Message.TABLENAME, null, message.getContentValues());
  	}
  
  	public void createAccount(Account account) {
  		SQLiteDatabase db = this.getWritableDatabase();
  		db.insert(Account.TABLENAME, null, account.getContentValues());
  	}
  
  	public void createContact(Contact contact) {
  		SQLiteDatabase db = this.getWritableDatabase();
  		db.insert(Contact.TABLENAME, null, contact.getContentValues());
  	}
  
  	public int getConversationCount() {
  		SQLiteDatabase db = this.getReadableDatabase();
  		Cursor cursor = db.rawQuery("select count(uuid) as count from "
  				+ Conversation.TABLENAME + " where " + Conversation.STATUS
  				+ "=" + Conversation.STATUS_AVAILABLE, null);
  		cursor.moveToFirst();
  		int count = cursor.getInt(0);
  		cursor.close();
  		return count;
  	}
  
  	public CopyOnWriteArrayList<Conversation> getConversations(int status) {
  		CopyOnWriteArrayList<Conversation> list = new CopyOnWriteArrayList<>();
  		SQLiteDatabase db = this.getReadableDatabase();
  		String[] selectionArgs = { Integer.toString(status) };
  		Cursor cursor = db.rawQuery("select * from " + Conversation.TABLENAME
  				+ " where " + Conversation.STATUS + " = ? order by "
  				+ Conversation.CREATED + " desc", selectionArgs);
  		while (cursor.moveToNext()) {
  			list.add(Conversation.fromCursor(cursor));
  		}
  		cursor.close();
  		return list;
  	}
  
  	public ArrayList<Message> getMessages(Conversation conversations, int limit) {
  		return getMessages(conversations, limit, -1);
  	}
  
  	public ArrayList<Message> getMessages(Conversation conversation, int limit,
  			long timestamp) {
  		ArrayList<Message> list = new ArrayList<>();
  		SQLiteDatabase db = this.getReadableDatabase();
  		Cursor cursor;
  		if (timestamp == -1) {
  			String[] selectionArgs = { conversation.getUuid() };
  			cursor = db.query(Message.TABLENAME, null, Message.CONVERSATION
  					+ "=?", selectionArgs, null, null, Message.TIME_SENT
  					+ " DESC", String.valueOf(limit));
  		} else {
  			String[] selectionArgs = { conversation.getUuid(),
  					Long.toString(timestamp) };
  			cursor = db.query(Message.TABLENAME, null, Message.CONVERSATION
  					+ "=? and " + Message.TIME_SENT + "<?", selectionArgs,
  					null, null, Message.TIME_SENT + " DESC",
  					String.valueOf(limit));
  		}
  		if (cursor.getCount() > 0) {
  			cursor.moveToLast();
  			do {
  				Message message = Message.fromCursor(cursor);
  				message.setConversation(conversation);
  				list.add(message);
  			} while (cursor.moveToPrevious());
  		}
  		cursor.close();
  		return list;
  	}
  
  	public Conversation findConversation(final Account account, final Jid contactJid) {
  		SQLiteDatabase db = this.getReadableDatabase();
  		String[] selectionArgs = { account.getUuid(),
  				contactJid.toBareJid().toString() + "/%",
  				contactJid.toBareJid().toString()
  				};
  		Cursor cursor = db.query(Conversation.TABLENAME, null,
  				Conversation.ACCOUNT + "=? AND (" + Conversation.CONTACTJID
  						+ " like ? OR "+Conversation.CONTACTJID+"=?)", selectionArgs, null, null, null);
  		if (cursor.getCount() == 0)
  			return null;
  		cursor.moveToFirst();
  		Conversation conversation = Conversation.fromCursor(cursor);
  		cursor.close();
  		return conversation;
  	}
  
  	public void updateConversation(final Conversation conversation) {
  		final SQLiteDatabase db = this.getWritableDatabase();
  		final String[] args = { conversation.getUuid() };
  		db.update(Conversation.TABLENAME, conversation.getContentValues(),
  				Conversation.UUID + "=?", args);
  	}
  
  	public List<Account> getAccounts() {
  		List<Account> list = new ArrayList<>();
  		SQLiteDatabase db = this.getReadableDatabase();
  		Cursor cursor = db.query(Account.TABLENAME, null, null, null, null,
  				null, null);
  		while (cursor.moveToNext()) {
  			list.add(Account.fromCursor(cursor));
  		}
  		cursor.close();
  		return list;
  	}
  
  	public void updateAccount(Account account) {
  		SQLiteDatabase db = this.getWritableDatabase();
  		String[] args = { account.getUuid() };
  		db.update(Account.TABLENAME, account.getContentValues(), Account.UUID
  				+ "=?", args);
  	}
  
  	public void deleteAccount(Account account) {
  		SQLiteDatabase db = this.getWritableDatabase();
  		String[] args = { account.getUuid() };
  