I need to include an existing SQLiteDatabase in my Android app and I also want the ability to download and install a new db. I did some research and my first working solution came from here. I didn't like that solution, for one thing, it assumes that the database will always be in a fixed path and other oddities.
So, rather than putting the existing database file in the assets, I exported the database to a SQL file, read it in, and then in the onCreate() method of my SQLiteOpenHelper, I call a new method updateDatabase with an open DataInputStream with the file data.
I ran into a few issues, which I think I solved, but I'm sure I didn't think of all the issues, which are:
When SQLiteOpenHelper's onCreate method is called, the database has been created, it is open, and inTransaction() is true. As a result, if the imported sql file includes BEGIN TRANSACTION, an exception is thrown and if the sql String contains statements creating 'android_metadata' yet another exception. So, I added a simple search using String.contains() looking for these keywords, and set a boolean doExecute to false to avoid executing them. So a question is, is there a better SQL class or method to filter this, or even a better regexp method?
Similar issue with having unexpected line breaks in the SQL file. I read the file with readLine() and to look for line breaks, I simply use String.trim() on the line, then check for endsWith(";"). This puts some constraints on my input file, like not having multiple statements on a single line. So, is there a better way to pre-process SQL from a file?
Here's the code I use to create my db after I've gotten a DataInputStream from the assets resource or from a download:
public boolean updateDatabase(DataInputStream inStream, SQLiteDatabase db, boolean doClear) throws Error {
String sqlStatement = null;
boolean result = true;
boolean inOnCreate = true;
boolean wasInTransaction;
if(doClear) dropDatabase();
// if called from onCreate() db is open and inTransaction, else getWritableDatabase()
if(db == null) {
inOnCreate = false;
db = this.getWritableDatabase();
}
wasInTransaction = db.inTransaction(); // see NB below
boolean doExecute;
try {
while ((sqlStatement = inStream.readLine()) != null) {
// trim, so we can look for ';'
sqlStatement.trim();
if(!sqlStatement.endsWith(";")) {
continue; // line breaks in file, get whole statement
}
// NB - my file (exported from SQLite Database Browser starts with "BEGIN TRANSACTION;".
// executing this throws SQLiteException: cannot start a transaction within a transaction
// According to SQLiteDatabase doc for beginTransaction(), "Transactions can be nested"
// so this is a problem
// but... possibly it is an "exclusive transaction" ?
doExecute = true;
if(wasInTransaction) {
// don't execute BEGIN TRANSACTION; or COMMIT;
if((sqlStatement.contains("BEGIN" ) || sqlStatement.contains("begin" )) &&
(sqlStatement. contains("TRANSACTION") || sqlStatement.contains("transaction" ))) {
doExecute = false;
}
if(sqlStatement.contains("COMMIT") || sqlStatement.contains("commit")) {
doExecute = false;
}
} // inTransaction
// this statement could be in older databases, but this scheme doesn't need, can't have it
if(sqlStatement.contains("android_metadata")) {
doExecute = false;
}
if(doExecute) {
try {
db.execSQL(sqlStatement);
} catch (SQLException e) {
throw(new Error("Error executing SQL " + sqlStatement));
} // try/catch
} // doExecute
} // while()
} catch (IOException e) {
result = false; // which won't matter if we throw
throw(new Error("Error reading " + DB_SQL));
}
if(!inOnCreate) {
db.close();
}
return result;
}
Wouldn't want to have you cop out early on such ambitious and elegant implementations, but if you have your database already made and checked with a database browser and all, have you considered SQLite Asset Helper? If your main issue was being forced to use the asset folder, this method lib let's you use a file from any specified directory. Moreover, it allows for handling the raw .db file. Worth checking out.
Related
I see in the Crashlytics-Logs of my android application a NullPointerException in this code:
try {
mSQLDBreader = this.getReadableDatabase();
} catch (SQLException e) {
if (mSQLDBreader != null) {
mSQLDBreader.close();
mSQLDBreader = this.getReadableDatabase();
}
}
mSQLDBreader... // NPE
As the previous developer isn't available any more, I don't know why it is tried two times, but the code seems to work sometimes, but often not. What can be reasons that this call returns null?
It seems like if this only happens on 2.3.x-devices, in my crashlogs all the affected devices are 2.3.5 and 2.3.6.
Do you have any threading going on of your own creation? Some code that might be resetting mSQLDBreader via another method. Perhaps that thread occasionally runs and trashes the value of mSQLDBreader before you use it?
Have you ever witnessed this on an emulator running 2.3.x?
I looked at google's code for getReadableDatabase, and I don't see a way that it could return null. Gory details are below if you are interested. Based on what I see, I would suspect either a multithreading bug in your code, or a bug introduced by customizations to the android code by the manufacturer of the devices you tested (if that is even plausible.)
Gory details All paths through getReadableDatabase invoke methods on the return object after creating it. So the value can't be null at that point. Otherwise the NPE would be raised from inside.
Here is a snippet of the 2.3.6 code for getReadableDatabase. Actual source is available on grepcode.
public synchronized SQLiteDatabase getReadableDatabase() {
if (mDatabase != null && mDatabase.isOpen()) {
return mDatabase; // The database is already open for business
}
if (mIsInitializing) { /* snip throw ISE */ }
try {
return getWritableDatabase();
} catch (SQLiteException e) {
// snip : throws or falls through below
}
SQLiteDatabase db = null;
try {
mIsInitializing = true;
String path = mContext.getDatabasePath(mName).getPath();
db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READONLY);
// *** next line calls method on db. NPE would be here if db was null at this point. ***
if (db.getVersion() != mNewVersion) {
// snip throw.
}
onOpen(db);
Log.w(TAG, "Opened " + mName + " in read-only mode");
mDatabase = db;
return mDatabase;
} finally {
// snip : not relevant
}
}
Notice that getReadableDatabase usually just returns the result of getWritableDatabase. He looks like this:
public synchronized SQLiteDatabase getWritableDatabase() {
if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) {
return mDatabase; // The database is already open for business
}
if (mIsInitializing) {
throw new IllegalStateException("getWritableDatabase called recursively");
}
// snip comment about locking
boolean success = false;
SQLiteDatabase db = null;
if (mDatabase != null) mDatabase.lock();
try {
mIsInitializing = true;
if (mName == null) {
db = SQLiteDatabase.create(null);
} else {
db = mContext.openOrCreateDatabase(mName, 0, mFactory);
}
int version = db.getVersion(); // ** method called on result!
// snip block that has more method calls and never nulls out db
onOpen(db);
success = true;
return db;
} finally {
// snip
mDatabase = db;
// snip rest of finally block that isn't relevant.
}
}
Lastly, it is important to note that both of these methods, as well as the close method of SqliteOpenHelper, are tagged with synchronize, so there is no way for one method to trash the state of the other if you have multiple threads calling these methods at the same time..
I have ran into similar problem in the past. It seems like keep closing and opening the database created this problem for me. If you are using the SQLLiteOpenHelper you should not be closing your database unless you have a really good reason to. See CommonsWare answer here which says
SQLiteOpenHelper holds onto the database you retrieve with
getReadableDatabase()/getWritableDatabase(), and the point is for you
to reuse that opened SQLiteDatabase object, particularly as you do
work across multiple threads.
open dataBase before use
if (mDatabase != null && mDatabase.isOpen()) {
return mDatabase; // The database is already open for business
} else {
return mDatabase.open();
}
I have two databases, one database is the primary. This primary DB is responsible for holding the current data which is up to date and my secondary DB is populated via a cron job, once the primary DB gets obsolete I want to replace it with the secondary DB via a file operation of just over writing the existing DB and refreshing my views. Is it possible to do this, is there a better way?
So far what I have done is:
public void writeToSD() throws IOException {
File f=new File("/mnt/sdcard/dump.db");
FileInputStream fis=null;
FileOutputStream fos=null;
try{
fis=new FileInputStream(f);
fos=new FileOutputStream("/data/data/com.one.two/databases/Bdr");
while(true){
int i=fis.read();
if(i!=-1){
fos.write(i);
}
else{
break;
}
}
fos.flush();
}
catch(Exception e){
e.printStackTrace();
}
finally{
try{
fos.close();
fis.close();
}
catch(IOException ioe){
System.out.println(ioe);
}
}
How about always using the same database files (let's say dbA, dbB) with two instances of SQLiteOpenHelper and using an utility class like this instead of using raw SQLiteOpenHelper:
class Db {
private SQLiteOpenHelper mPrimaryDb;
private SQLiteOpenHelper mSecondaryDb;
public Db(Context context) {
mPrimaryDb = new MyDbHelper(context, "db_a");
mSecondaryDb = new MyDbHelper(context, "db_b");
}
public SQLiteOpenHelper getPrimaryDb() {
return mPrimaryDb;
}
public SQLiteOpenHelper getSecondaryDb() {
return mSecondaryDb;
}
public void swapDb() {
SQLiteOpenHelper tmp = mPrimaryDb;
mPrimaryDb = mSecondaryDb;
mSecondaryDb = tmp;
// TODO: notify data users that data has changed, cleanup the old primary database, etc.
}
{
If you want to use file operations, renaming the data base files is faster. But during file operations all connections have to be closed before any action.
If insertion is too slow, I would not overwrite the database file. I would generate the new database with a temp name and the same table and view structure. After finishing writing to the temp file I would rename the file to the same name as the invariant part of the old database plus a version number or a timestamp . And in my application I would look periodically for a new version, if found I would close all connections to the old file and open the new database.
I'm trying to insert 100000 records in android sqlite database at a time. I'm using following two different methods.
private void bulkInsertDataBySavePoint(final List<User> users) {
log.debug("bulkInsertDataBySavePoint()");
DatabaseConnection conn = null;
Savepoint savepoint = null;
try {
conn = userDao.startThreadConnection();
savepoint = conn.setSavePoint("bulk_insert");
for (User user : users) {
userDao.create(user);
}
} catch (SQLException e) {
log.error("Something went wrong in bulk Insert", e);
} finally {
if (conn != null) {
try {
conn.commit(savepoint);
userDao.endThreadConnection(conn);
} catch (SQLException e) {
log.error("Something went wrong in bulk Insert", e);
}
}
}
}
And
private void bulkInsertDataByCallBatchTasks(final List<User> users) {
log.debug("bulkInsertDataByCallBatchTasks()");
try {
userDao.callBatchTasks(new Callable<Void>() {
#Override
public Void call() throws Exception {
for (User user : users) {
userDao.create(user);
}
return null;
}
});
} catch (Exception e) {
e.printStackTrace();
}
}
Both methods work fine. On average they take 140 seconds and take 60-65% CPU which is not ok, I think.
The idea is, I have to consume an api which will provide json data. I have to parse that json data and then insert into sqlite database for offline usage.
I'm looking for an efficient way to solve this issue.
Any thought?
I'm trying to insert 100000 records in android sqlite database at a time... On average they take 140 seconds and take 60-65% CPU which is not ok in my opinion.
Unfortunately I don't have an easy answer for you. You may have to do this sort of insert directly using raw SQL to achieve faster performance on the limited Android CPU. Once you have the data inserted then you can turn to ORMLite to query or manipulate the data faster.
I've had the same problem, and found a reasonable workaround. This took insert time from 2 seconds to 150ms:
final OrmLiteSqliteOpenHelper myDbHelper = ...;
final SQLiteDatabase db = myDbHelper.getWritableDatabase();
db.beginTransaction();
try{
// do ormlite stuff as usual, no callBatchTasks() needed
db.setTransactionSuccessful();
}
finally {
db.endTransaction();
}
Hrm. Good idea #FarrukhNajmi. I've just added it to trunk. It will be in version 4.49.
#Gray Is it still unstable? when can we see it in maven?
And if com.j256.ormlite.dao.ForeignCollection#addAll make only one request it would be nice too.
I use the following code to add rows to my database :
public void insert(String kern, String woord) {
SQLiteDatabase db = getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KERN, kern);
values.put(WOORD, woord);
db.insertOrThrow(TABLE_NAME, null, values);
return;
Currently, I'm invoking this insert() 3.455 times, to add all words to the database, using : insert("Fruits", "Banana"); It takes forever.
How can I change this code to work faster? I'm thinking in the line of foreach, but don't know how to implement.. Thanks!
/Edit; The solution provided by #hovanessyan works and will do the job. AND.. note that if you have a lot of lines that have to be put in, you might be confronted with the method exceeds max byte limit error. In that case, review the other solution, that suggests packing the database in the actual .APK file.
You can wrap-up those inserts into transaction.
db.beginTransaction();
try {
// do all the inserts here
//method call here, that does 1 insert; For example
addOneEntry(kern,woord);
...
db.setTransactionSuccessful();
} catch (SQLException e) {
//catch exceptions
} finally {
db.endTransaction();
}
private void addOneEntry(String kern, String woord) {
//prepare ContentValues
//do Insert
}
You can use bulkInsert:
ContentValues[] cvArr = new ContentValues[rows.size()];
int i = 0;
for (MyObject row : rows) {
ContentValues values = new ContentValues();
values.put(KERN, myObject.getKern());
values.put(WOORD, myObject.getWoord);
cvArr[i++] = values;
}// end for
resolver.bulkInsert(Tasks.CONTENT_URI, cvArr);
Using the tips of both hovanessyan and Damian (remind me to rep+1 you as soon as I reach 15 ;), I came up with the following solution:
For relatively small databases (<1,5Mb)
I created the database using SQLite Database Browser, and put it in my Assets folder.
Then, the following code copies the database to the device, if it's not already there:
boolean initialiseDatabase = (new File(DB_DESTINATION)).exists();
public void copyDB() throws IOException{
final String DB_DESTINATION = "/data/data/happyworx.nl.Flitswoorden/databases/WoordData.db";
// Check if the database exists before copying
Log.d("Database exist", "" + initialiseDatabase);
Log.d("Base Context", "" + getBaseContext());
if (initialiseDatabase == false) {
// Open the .db file in your assets directory
InputStream is = getBaseContext().getAssets().open("WoordData.db");
// Copy the database into the destination
OutputStream os = new FileOutputStream(DB_DESTINATION);
byte[] buffer = new byte[1024];
int length;
while ((length = is.read(buffer)) > 0){
os.write(buffer, 0, length);
}
os.flush();
os.close();
is.close();
}}
In my app, a portion of the database is User-customizable.
I call the code above in onStart() with :
try {
copyDB();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
So, when the user presses "reset database to standard" (in preferences screen), I just set the Boolean initialiseDatabase to "false" and wait for the user to go back to the main activity. (thus calling onstart and copying the original database).
I tried to call the Activity.copyDB() from the preferences.java. It's neater, because it doesn't require the user to go back to the main activity to rebuild the database. However, I get an error about not being able to call static references to non-static methods. I don't understand that, but will look into it.
SqliteOpenHelper by default creates database in mode_private. How can we create world readable/writable db using SqliteOpenHelper ?
Or Else Do I need to use Context.openOrCreateDatabase()
How can we create world readable/writable db using SqliteOpenHelper ?
We can't do that. ContextImpl.openOrCreateDatabase() actually opens/creates database using SQLiteDatabase.openOrCreateDatabase() method and then sets the permission for the database file using class android.os.FileUtils which is not part of the public API. So unless you want to use reflection the only possible way to make database world-readable/-writable is to use Context.openOrCreateDatabase().
Opening a Database as world Readable/writable is definitely possible. But then what is the necessity of a Database? You can use files instead..!!
Opening a Database as world Readable/writable is not recommended.
Always remember this:
Open a database only when necessary,
because it is costly.
Open only in the mode necessary either
read or write or both.
Close it as soon as the manipulations
are over.
If you want to share a Database or a resource among your applications you can use SharedUserID. Inorder to use SharedUserID, the applications must be signed by the same Key.
For More info see my post here at sree.cc
http://sree.cc/google/android/sharing-resources-in-different-aplications-using-shareduserid
Here is the code Snippet for the same:
private void getDB() {
//accessing file using SHAREDUSERID
try
{
//creating context from mainAPP for accessing database
ctx = createPackageContext(
"com.schogini.sharedDB.pack",
Context.CONTEXT_IGNORE_SECURITY);
if(ctx==null){
return;
}
}
catch (PackageManager.NameNotFoundException e) {
//package not found
Log.e("Error",e.getMessage());
}
try
{
File myDbFile = ctx.getDatabasePath("sharedDB.db");
if (myDbFile.exists())
{
dbb = openOrCreateDatabase(myDbFile.getPath(), SQLiteDatabase.OPEN_READWRITE, null);
dbb.setVersion(1);
dbb.setLocale(Locale.getDefault());
dbb.setLockingEnabled(true);
try{
cur=dbb.rawQuery("select * from TABLENAME;",null);
try{
cur.moveToFirst();
int k=cur.getColumnCount();
lv_arr=new String[k];
for(int i=0;i<k;i++)
{
lv_arr[i]=""+cur.getString(i);
Toast.makeText(LaunchActivity.this, "Data "+i, Toast.LENGTH_SHORT).show();
}
}
catch(Exception e)
{
//may be an empty database
Log.e("Error",e.getMessage());
dbb.close();
}
}
catch(Exception e)
{
Log.e("Error",e.getMessage());
dbb.close();
}
}
else
{
//database not found
Toast.makeText(LaunchActivity.this, "DataBase Doesnot Exist", Toast.LENGTH_SHORT).show();
}
}
catch(Exception e)
{
Log.i("\n\nTAG",e.toString());
}
}
Not recommended:
If you want the word readable, then create it world readable. Use openFileOutput() or openOrCreateDatabase(). Declare the context that creates the DB as World readable. Note this method is not safe by any means.
Do a reference here.
http://developer.android.com/reference/android/content/Context.html#MODE_WORLD_READABLE