CODEWITHSUNDEEP
iphonedatabasesqlite
coder
coder

Reputation: 10520

sqlite error database is locked

I am have a sqlite database in the iPhone application I am writing. I get an error with following code that I am running in a background thread. In the background thread, I call this method:

 - (BOOL) songIsInDatabase:(NSString *)songTitle
{
NSString *docsDir;
NSArray *dirPaths;

dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];


//Build the path to the database file
NSString *databasePath = [[NSString alloc] initWithString:[docsDir stringByAppendingPathComponent:@"Database.db"]];

const char *dbpath = [databasePath UTF8String];

sqlite3_stmt *statement;

if(sqlite3_open(dbpath, &DB) == SQLITE_OK){

    NSString *insertSQL = [NSString stringWithFormat:@"select * from Bpm_Table where song_title = '%@'", songTitle];

    const char *insert_stmt = [insertSQL UTF8String];
    if(sqlite3_prepare_v2(DB, insert_stmt, -1, &statement, NULL) == SQLITE_OK)
    {
        while (sqlite3_step(statement) == SQLITE_ROW)
        {
            return YES;
            break;
        }
    }else{
        NSLog(@"the error is %s", sqlite3_errmsg(DB));
    }
    sqlite3_finalize(statement); 
}

[databasePath release];
return NO;
}

Then I call this method:

- (void) addSongToDatabase: (NSString *) songTitle andBPM: (int)bpm andGenre: (NSString *) genre
{
NSString *docsDir;
NSArray *dirPaths;

dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];


//Build the path to the database file
NSString *databasePath = [[NSString alloc] initWithString:[docsDir stringByAppendingPathComponent:@"Database.db"]];

const char *dbpath = [databasePath UTF8String];

sqlite3_stmt *statement;

if(sqlite3_open(dbpath, &DB) == SQLITE_OK){

    NSString *insertSQL = [NSString stringWithFormat:@"insert or replace into Bpm_Table (song_title, bpm, genre) values (\"%@\", \"%d\", \"%@\")", songTitle, bpm, genre];

    const char *insert_stmt = [insertSQL UTF8String];
    if(sqlite3_prepare(DB, insert_stmt, -1, &statement, NULL) == SQLITE_OK){
        if(sqlite3_step(statement) == SQLITE_DONE)
        {

        } else {
            NSLog(@"error: %s", sqlite3_errmsg(DB));
        }
    }sqlite3_finalize(statement);
}

[databasePath release];
}

If I run both these methods, one right after the other, I get an error that says database is locked. I added the sqlite3_finalize statements after poking around google in hopes that would fix the issue. If I comment out either of the methods, I don't get this error.

Does anyone know what's wrong?

Upvotes: 7

Views: 42850

Answers (7)

turingtested
turingtested

Reputation: 7154

If you have tried sqlite3_close(DB) it's probably because your methods are trying to access the same database at the same time. Try this line of code

sqlite3_busy_timeout(DB, 500);

somewhere between sqlite3_open and sqlite3_prepare_v2 in the method from where you get the "database is locked"-error.

The database-connection will then try to write/read in 500 milliseconds before it gives up, which is usually enough time to escape the locking.

Upvotes: 5

Pinkoy Montano
Pinkoy Montano

Reputation: 1

I had the same problem a while ago. I tried copying the database file itself, renamed it to different filename, then checked it - It actually WORKED!

I am using SQLite3.

I hope this will also work for you!

Upvotes: -3

prashant wadi
prashant wadi

Reputation: 41

Your database is open. Close it using sqlite3_close(db).

If you don't close, then the process accessing your database will be running background which will cause database is locked error.

Upvotes: 3

vinayak jadi
vinayak jadi

Reputation: 959

your database is open close it using sqlite3_close(db) if you dont close then the process which accessed your database will be running background which will cause database is locked error.

if you want to remove database is locked error then follow these steps 1.copy your database file to some other location. 2.then replace the database with the copied database 3.this will dereference all processes which were accessing your database file

Upvotes: 5

Hot Licks
Hot Licks

Reputation: 47699

But note that if you access the same SQLite DB from multiple threads, without some sort of separate synchronization (some way to know that you'll never have near-simultaneous accesses from multiple threads) then you're likely to get "database locked" errors even if you close everything correctly on each access.

SQLite does not provide any sort of "lock wait" mechanism.

Your basic options are:

  1. Do all accesses from one thread.
  2. Use a separate lock protocol around all accesses.
  3. If you get a "database locked" error wait a brief period of time and retry.

Upvotes: 6

Saurabh
Saurabh

Reputation: 22873

you must always close the sqlite database after using it ... so add this line sqlite3_close(DB); just after sqlite3_finalize(statement);

Update -

You are returning YES in one of your while loop -

        while (sqlite3_step(statement) == SQLITE_ROW)
        {
            return YES;
            break;
        }

so here you are nither finalizing nor closing the database.. you need to close if everytime you open it

Upvotes: 13

meggar
meggar

Reputation: 1219

For one thing, you're not closing the database connection with sqlite3_close() before you open a new connection

Upvotes: 0

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