implementing WAL in iOS? - ios

Question

The code I placed below works. So my scenario is I have the code below in a class. I use this class simply for merging tables and updating one table. When I call the object that this code lives in the app delegate for example, it works great! But when I call the same object after clicking a button in a tableview controller, I get a database lock error. So here's what I am wondering. After reading sqlite documentation WAL: http://www.sqlite.org/wal.html I am thinking that I cannot read and update concurrently to the sqlite db, right? I am unsure of a solution around this, so what would be a good suggestion around my problem. Remember, keep in mind this code works just fine in the app delegate, it does not work in my tableview controller when I call it using action upon clicking the button. Note: I SELECT data from the SQLITE database to display table cell names etc. Thanks ahead of time!
//Allocates a filemanager object. Ideally, this object is used for searching through the applications context
NSFileManager *fileManager = [NSFileManager defaultManager];
BOOL dbErr = NO;
//Boolean variable to tell if the database exists
BOOL error,mainDbError;
//Looks through all the databases. If there is a database that does not exist, the following error message will appear to the user. If all the databases exist on the system, the database opens respectively
error = [self checkAndOpenSyncDB];
mainDbError = [self checkAndOpenMainDB];
if (!error&&mainDbError) {
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"Oops!"
message:#"We didn't mean for this to happen. Looks like there was a problem loading the sync database. Contact technical support for further assistance."
delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alertView show];
}
else{
//This is I think to check when the last time the sync occured on the system.. not quite sure though1
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
NSLog(#"Erorr syncing the database: Code: %d, message: '%s'", error,sqlite3_errmsg(syncOpenHandle));
char *errorMessage;
int errorNum = 0;
//Atataching the sync db to the master db
NSString *attachSQL = [NSString stringWithFormat:#"ATTACH DATABASE \'%#\' AS sync_db", self->pathForSync];
NSLog(#"PATH FOR SYNC !!!!!!! %#", pathForSync);
NSLog(#"Here's the arratch string: %#", attachSQL);
//
if (sqlite3_exec(syncOpenHandle, [attachSQL UTF8String], NULL, NULL, &errorMessage) == SQLITE_OK) {
NSString *masterQuery = [NSString stringWithFormat:#"SELECT name FROM sqlite_master WHERE type='table';"];
const char *masterStmt = [masterQuery UTF8String];
sqlite3_stmt *statement;
BOOL loopErr;
loopErr = sqlite3_prepare_v2(syncOpenHandle, masterStmt, -1, &statement, NULL);
if (sqlite3_prepare_v2(syncOpenHandle, masterStmt, -1, &statement, NULL)==SQLITE_OK) {
while (sqlite3_step(statement) == SQLITE_ROW) {
NSString * currentTable = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 0)];
NSLog(#"Here's the current table: %#",currentTable);
//This is where the magic happens. If there are any keys matching the database, it will update them. If there are no current keys in the database, the query will insert them.
if ([currentTable isEqualToString:#"USER_DATA"] == NO && [currentTable isEqualToString:#"USER_ACTIVITY"]== NO && [currentTable isEqualToString:#"USER_ITINERARY"] == NO) {
NSString *tblUpdate = [NSString stringWithFormat:#"INSERT or REPLACE INTO main.%# SELECT * FROM sync_db.%#;",currentTable, currentTable];
const char *updateStmt = [tblUpdate UTF8String];
//sqlite3_busy_timeout (mainOpenHandle, 60000);
bool update;
update = sqlite3_exec(syncOpenHandle, updateStmt, NULL, NULL, &errorMessage)== SQLITE_OK;
NSLog(#"Error sync ... '%s'", sqlite3_errmsg(syncOpenHandle));
if (sqlite3_exec(syncOpenHandle, updateStmt, NULL, NULL, &errorMessage)== SQLITE_OK) {
NSLog(#"Error sync ... '%s'", sqlite3_errmsg(syncOpenHandle));
if (errorNum == 1) {
//A database reset is needded
//self->isResetDataBase = YES;
}
dbErr = YES;
}
}
}
NSLog(#"Error sync ... '%s'", sqlite3_errmsg(syncOpenHandle));
}
NSLog(#"Here's the error num %d", errorNum);
NSLog(#"Erorr syncing the database: Code: %d, message: '%s'", error,sqlite3_errmsg(syncOpenHandle));
NSLog(#"Error sync ... '%s'", sqlite3_errmsg(syncOpenHandle));
sqlite3_finalize(statement);
//Detaching the database from the mainDB
NSString *detachSQL = [NSString stringWithFormat:#"DETACH DATABASE sync_db"]; // reference sync db
if ((errorNum = sqlite3_exec(syncOpenHandle, [detachSQL UTF8String], NULL, NULL, &errorMessage))!= SQLITE_OK) {
NSLog(#"Detatched syncDb Failed. ErrorMessage = %s ", errorMessage);
}
}
}
NSLog(#"Error sync ... '%s'", sqlite3_errmsg(syncOpenHandle));
//Closing the database when finished.
if (syncOpenHandle!=nil) {
sqlite3_close(syncOpenHandle);
NSError *err;
int success = [fileManager fileExistsAtPath:pathForSync];
if (success) {
[[NSFileManager defaultManager]removeItemAtPath:pathForSync error:&err];
}
}