FMDatabaseQueue error: database is locked
I have a method that runs on a background thread and so (as I understand it) I need to use FMDatabaseQueue
to access my SQLite database safely and reliably.
I make a request to check if a record exists, after which I immediately UPDATE
or INSERT
depending on the result.
The first request runs fine and I get an invoice, but then the next request fails. Here is the error I am getting:
Unknown error when calling sqlite3_step (5: database 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 request SELECT
from others in some way ? Any idea why my database is locked after the first request?
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I have the same problem. I did sharedInstance with a 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];
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