Hey Mirko, thank you very much for taking the time to give me such a detailed and easy to understand answer.
I think that I already have implemented my code the way you describe as I originally started out with the Notepad example<http://developer.android.com/guide/tutorials/notepad/notepad-ex1.html>and that does it the same way. Except that I don't use transactions. However in the lock situation from above (see the two stack traces I quoted above) the concurrent accesses were reads, so the transactions idea doesn't apply, or does it? Reading your mail I thought of something else. Maybe I should open a read only database? That would be a separate instance then. mAllPurposeDatabase = dbOpenerHelper.getWritableDatabase(); mSlowQueryDatabase = dbOpenerHelper.getReadableDatabase(); And then I will direct the slow queries always to the 2nd instance. It wouldn't matter much if the database contains old data, it's just used for search. I may setLockingEnabled()<http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html#setLockingEnabled(boolean)>to false, but as the queries are slow it probably won't matter much. Something completely different. Do you use close() on the database at all? If so, when? Cheers, Mariano On Fri, Oct 23, 2009 at 7:16 PM, mirko <[email protected]> wrote: > > Hi Mariano, > > I had the same problems with my app. After reading a little bit on the > SQLite Website my understanding was that locking is done with process > (thread) locks. So there are many reader treads possible, but only one > writer thread. For this reason your SQLiteDatabase object needs to be > a singleton. I think otherwise the database file will be opened > several times. In my app I get the singleton with: > > mDatabase = dbOpenerHelper.getWritableDatabase(); > > This is only called once and every call to the Database uses the same > mDatabase object, > > Every time I read in the database I do not open a transaction, only a > cursor, like this: > > public static PlaylistItem queryCurrentTrackInDB(SQLiteDatabase db, > String playlistID) { > PlaylistItem ret = null; > String whereClause = PlaylistItem.COL_PLAYLIST_ID + "=?"; > String[] whereValues = new String[] { playlistID }; > String orderClause = PlaylistItem.COL_CURRENT_TRACK + " > DESC," + > PlaylistItem.COL_NUMBER; > Cursor cur = db.query(IConstants.PLAYLIST_TABLE, null, > whereClause, > whereValues, null, null, orderClause, "2"); > if (cur.moveToFirst()) { > ret = new PlaylistItem(cur); > } > cur.close(); > return ret; > } > > > Every time I write to the database I use a transaction: > > public static boolean deletePlaylistByID(SQLiteDatabase db, String > playlistID) { > db.beginTransaction(); > int r = 0; > try { > String whereClause = PlaylistItem.COL_PLAYLIST_ID + > "=?"; > String[] whereValues = new String[] { playlistID}; > r = db.delete(IConstants.PLAYLIST_TABLE, > whereClause, whereValues); > db.setTransactionSuccessful(); > } finally { > db.endTransaction(); > } > return r > 0; > } > > I have a lot of concurrency in my app and after changing it the > described way it works quite well. > > Mirko > > On 23 Okt., 18:14, Mariano Kamp <[email protected]> wrote: > > Hi, > > > > I have implemented a slow search provider that queries my database. Now > > when at the same time I do another read access my applications stalls > (ANR). > > > > It's both read and I don't see why there should be a lock. What are my > > options to get a little more concurrency here? > > > > Cheers, > > Mariano > > > > Here are the two threads that block each other. > > > > One: > > "main" prio=5 tid=3 WAIT > > | group="main" sCount=1 dsCount=0 s=N obj=0x4001db08 self=0xbc48 > > | sysTid=2680 nice=0 sched=0/0 handle=-1343996920 > > at java.lang.Object.wait(Native Method) > > - waiting on <0x271f30> (a java.lang.VMThread) > > at java.lang.Thread.parkFor(Thread.java:1499) > > at java.lang.LangAccessImpl.parkFor(LangAccessImpl.java:48) > > at sun.misc.Unsafe.park(Unsafe.java:319) > > at java.util.concurrent.locks.LockSupport.park(LockSupport.java:117) > > at > > > java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:680) > > at > > > java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:710) > > at > > > java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1040) > > at > > > java.util.concurrent.locks.ReentrantLock$FairSync.lock(ReentrantLock.java:193) > > at > java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:252) > > at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:292) > > at > > > android.database.sqlite.SQLiteDatabase.addSQLiteClosable(SQLiteDatabase.java:221) > > at android.database.sqlite.SQLiteProgram.<i > > nit>(SQLiteProgram.java:57) > > at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:49) > > at > > > android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:49) > > at > > > android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1118) > > at > > android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1092) > > at com.newsrob.DB.findCursorByQueryString(DB.java:419) > > at com.newsrob.EntryManager.getArticleAsCursor(EntryManager.java:1010) > > at > > > com.newsrob.activities.ShowArticleActivity.onCreate(ShowArticleActivity.java:81) > > at > > > android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123) > > at > > > android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364) > > at > > android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417) > > at android.app.ActivityThread.access$2100(ActivityThread.java:116) > > at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794) > > at android.os.Handler.dispatchMessage(Handler.java:99) > > at android.os.Looper.loop(Looper.java:123) > > at android.app.ActivityThread.main(ActivityThread.java:4203) > > at java.lang.reflect.Method.invokeNative(Native Method) > > at java.lang.reflect.Method.invoke(Method.java:521) > > at > > > com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) > > at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) > > at dalvik.system.NativeStart.main(Native Method) > > > > Two: > > "Binder Thread #4" prio=5 tid=17 NATIVE > > | group="main" sCount=1 dsCount=0 s=N obj=0x432685c8 self=0x231ee8 > > | sysTid=2690 nice=10 sched=0/0 handle=2315224 > > at android.database.sqlite.SQLiteQuery.native_fill_window(Native > Method) > > at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:75) > > at > android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:288) > > at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:269) > > at > android.database.AbstractCursor.moveToPosition(AbstractCursor.java:171) > > at android.database.AbstractCursor.moveToNext(AbstractCursor.java:256) > > at > > com.newsrob.search.SearchProvider.getSuggestions(SearchProvider.java:80) > > at com.newsrob.search.SearchProvider.query(SearchProvider.java:68) > > at > > > android.content.ContentProvider$Transport.bulkQuery(ContentProvider.java:116) > > at > > > android.content.ContentProviderNative.onTransact(ContentProviderNative.java:97) > > at android.os.Binder.execTransact(Binder.java:287) > > at dalvik.system.NativeStart.run(Native Method) > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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