iOS Large SQLite data set slow performance - ios

Question

I have an application that I am working on for iOS that is to display trails on a map based on the bounding box of the current view. So as the user moves around the map it will load the appropriate set of trails.
The SQLite table is LARGE, 260k rows, where each row is a point on a trail. The table has a primary key (int), latitude (float), longitude (float) and a name (varchar). The latitude and longitude columns are indexed. When I query I am looking for where the latitude is between the lower right and upper left latitude and the longitude is between the upper left and lower right longitude. The query works flawlessly on desktop as well as on the phones as it returns the expected results. The issue is that on my Mac the query returns instantaniously where as on the phone it may take as little as 4 seconds before returning anything. The bottle neck does appear to be the database query and I'm starting to think its a limitation of the hardware.
I have tried using CoreData which is where I noticed the issue first. Then I moved to using FMDB to access the database and am still having issues.
I have done no tweaking to the database or to the connection.
The guts of the queryForTrails method
if( ![db open] ) {
[db release];
NSLog(#"Error opening DB: %#", dbPath);
}
FMResultSet *trails = [db executeQueryWithFormat:#"SELECT zname, zlatitude, zlongitude FROM ztrail WHERE ztype = 1 and zlatitude BETWEEN %# and %# AND zlongitude BETWEEN %# and %# order by zname", lrLat, ulLat, ulLon,lrLon];
//Start to load the map with data
NSString *lastTrailName=#"";
int idx = 0;
CLLocationCoordinate2D *trailCoords = nil;
NSUInteger coordSize = 20;
trailCoords = malloc(sizeof(CLLocationCoordinate2D)*coordSize);
while( [trails next] ) {
NSString *trailName = [trails stringForColumnIndex:0];
NSString *lat = [trails stringForColumnIndex:1];
NSString *lon = [trails stringForColumnIndex:2];
if( [lastTrailName compare:trailName] != NSOrderedSame ) {
if(idx > 0) {
[trailLines addObject:[MKPolyline polylineWithCoordinates:trailCoords count:idx]];
free(trailCoords);
idx = 0;
coordSize = 20;
}
lastTrailName = trailName;
trailCoords = malloc(sizeof(CLLocationCoordinate2D)*coordSize);
}
if(idx == coordSize) {
coordSize *= 2;
trailCoords = realloc(trailCoords, sizeof(CLLocationCoordinate2D) * coordSize);
}
trailCoords[idx++] = CLLocationCoordinate2DMake([lat doubleValue], [lon doubleValue]);
}
//Build the new polyline
[trailLines addObject:[MKPolyline polylineWithCoordinates:trailCoords count:idx]];
//NSLog(#"Num Trails: %d", [trailLines count]);
free(trailCoords);
//NSLog(#"Num of Points %d for %#",idx, lastTrailName);
if( [trailLines count] > 0 ) {
dispatch_async(dispatch_get_main_queue(),^{
[mapView addOverlays:trailLines];
});
}
I can provide some NSLog data if needed. I will also be doing the same application for Android so I'd like to try and work out the performance issues now.