SQLite Exception: SQLite Busy

Question

Can anyone provide any input on this error. I am trying to insert into table using Objective C.

While I am doing this, I am getting an error SQLite Busy. Why this is happening?

Answer 1

If I get it right, "busy" means that you cannot obtain a lock. Seems that some another process (or thread, etc) has a lock on a database.

File Locking And Concurrency In SQLite Version 3

Answer 2

If you get as a result when invoking an sqlite3 function the error code SQLITE_BUSY, this means as observed by drdaeman that the db has been locked by the same process or by one thread within your process.

The proper way to deal with this situation is o try the operation in a loop, and if the return code is still SQLITE_BUSY, to wait for some time (you decide the timeout value) and then retry the operation in the next loop iteration.

For instance, the following code snippet is taken from the Objective C wrapper FMDB (http://code.google.com/p/flycode/source/browse/trunk/fmdb) shows how to prepare a statement for a query taking into account that some operations may return SQLITE_BUSY:

int numberOfRetries = 0;
BOOL retry          = NO;

if (!pStmt) {
    do {
        retry   = NO;
        rc      = sqlite3_prepare(db, [sql UTF8String], -1, &pStmt, 0);

        if (SQLITE_BUSY == rc) {
            retry = YES;
            usleep(20);

            if (busyRetryTimeout && (numberOfRetries++ > busyRetryTimeout)) {
                NSLog(@"%s:%d Database busy (%@)", __FUNCTION__, __LINE__, [self databasePath]);
                NSLog(@"Database busy");
                sqlite3_finalize(pStmt);
                [self setInUse:NO];
                return nil;
            }
        }
        else if (SQLITE_OK != rc) {


            if (logsErrors) {
                NSLog(@"DB Error: %d \"%@\"", [self lastErrorCode], [self lastErrorMessage]);
                NSLog(@"DB Query: %@", sql);
                if (crashOnErrors) {

                    NSAssert2(false, @"DB Error: %d \"%@\"", [self lastErrorCode], [self lastErrorMessage]);
                }
            }

            sqlite3_finalize(pStmt);

            [self setInUse:NO];
            return nil;
        }
    }
    while (retry);
}

By the way, if you need to access sqlite, FMDB is very handy and much simpler to use with respect to direct access through the native C APIs.