NSData and UIImage not released in iOS7 - ios

Question

I have a big table in SQLite where photos are stored with good resolution so they have a big size… so I am trying to resize these images and updating the DB table in the same process. I am using FMDB wrapper for working with SQLite DB.
Well, with instruments I can see NSData and UIImage is not being released and memory grows quickly so it makes my app close.
What could I do?
Here it is the code:
FMResultSet *aFMResultSet = [database executeQuery:#"SELECT id, image FROM Images WHERE LENGTH(image)> 1000000;" ];
while([aFMResultSet next]){
int aId = [aFMResultSet intForColumn:#"id"];
NSData *aDataImage = [aFMResultSet dataForColumn:#"image"];
UIImage* aImage = [UIImage imageWithData:aDataImage];
UIImage *aResizedImage = [Utils resizedImage:aImage withRect:CGRectMake(0, 0, 324, 242)]; //(2592x1936)/16
NSData *aDataResizedThumbnail = UIImageJPEGRepresentation(aResizedImage,0.5f);
[database executeUpdate:#"UPDATE Images SET image = ? WHERE id = ?;", aDataResizedThumbnail, [NSNumber numberWithInt:aId],nil];
}

Answer 1

Due to the loop, the system might never get a chance to free the memory not needed anymore.
To force the system to do so, wrap the inside of your loop in an autoreleasepool, like this:
FMResultSet *aFMResultSet = [database executeQuery:#"SELECT id, image FROM Images WHERE LENGTH(image)> 1000000;" ];
while([aFMResultSet next]){
int aId = [aFMResultSet intForColumn:#"id"];
#autoreleasepool {
NSData *aDataImage = [aFMResultSet dataForColumn:#"image"];
UIImage* aImage = [UIImage imageWithData:aDataImage];
UIImage *aResizedImage = [Utils resizedImage:aImage withRect:CGRectMake(0, 0, 324, 242)]; //(2592x1936)/16
NSData *aDataResizedThumbnail = UIImageJPEGRepresentation(aResizedImage,0.5f);
[database executeUpdate:#"UPDATE Images SET image = ? WHERE id = ?;", aDataResizedThumbnail, [NSNumber numberWithInt:aId],nil];
}
}