FMDatabaseQueue Error: database is locked - ios

Question

I have a method that runs in a background thread, and so (as I understand it) I need to use FMDatabaseQueue to safely and reliably access my SQLite database.
I'm doing a query to check for the presence of a record, after which I immediately UPDATE or INSERT depending on the result.
The first query runs fine and I get a count, but then the query that follows doesn't run. Here's the error I get:
Unknown error calling sqlite3_step (5: database is locked) eu
Here is my code:
//Establish database queue
NSString *path = [[PPHelpers documentsPath] stringByAppendingPathComponent:#"PilotPro2.db"];
FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:path];
//Start thread-safe database queue
[queue inDatabase:^(FMDatabase *dbq) {
NSUInteger count;
//The other parameters in this query are provided beforehand
NSString *query = [NSString stringWithFormat:#"SELECT COUNT(%#) AS counter FROM %# WHERE %# = '%#'",columnID, model, columnID, dict[columnID]];
FMResultSet *countResult = [dbq executeQuery:query]; //This works fine
while([countResult next]) {
count = [countResult intForColumn:#"counter"];
}
[countResult close];
if(count > 0){
//--- UPDATE
//-- This is where FMDB throws the error...
[dbq executeUpdate:[PPDatabase editAircraftQuery:dict[columnID]], dict[#"aircraftRegistration"], dict[#"makeModel"], dict[#"categoryClass"], dict[#"highPerformance"], dict[#"complex"], dict[#"turbine"], dict[#"turboprop"], dict[#"tailwheel"], dict[#"active"]];
}else{
//--- INSERT
[dbq executeUpdate:[PPDatabase addAircraftQuery], dict[#"aircraftID"], dict[#"aircraftRegistration"], dict[#"makeModel"], dict[#"categoryClass"], dict[#"highPerformance"], dict[#"complex"], dict[#"turbine"], dict[#"turboprop"], dict[#"tailwheel"], dict[#"active"]];
}
}];
Do I need to separate my SELECT query from the others somehow? Any idea why my database is locked after the first query?

Answer 1

I have the same issue. I made sharedInstance with global queue
context.h
#interface context : NSObject
{
FMDatabaseQueue *_queue;
}
+ (context *)sharedInstance;
#property(strong, nonatomic, readwrite) FMDatabaseQueue *queue;
#end
context.m
#import "context.h"
#implementation context
#synthesize queue = _queue;
+ (context *)sharedInstance {
static dispatch_once_t onceToken;
static context *instance = nil;
dispatch_once(&onceToken, ^{
instance = [[context alloc] init];
});
return instance;
}
- (id)init {
self = [super init];
if (self) {
_queue = [FMDatabaseQueue databaseQueueWithPath:YOUR_SQLITE_FILE_PATH];
}
return self;
}
#end
How to use it
context *appContext = [context sharedInstance];
[appContext.queue inDatabase:^(FMDatabase *db) {
FMResultSet *results = [db executeQuery:#"SELECT * FROM something"];
if([results next]) {
NSLog(#"results dump = %#", [results resultDictionary]);
}
[results close];