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Issue Description and Steps

When you have a ImageView in your tableview cell.
1.The page landing API responds and set image url to the imageView, SD start( T0) to load the picture(100ms).
2. at T0 + 50 ms, some logic trigger tableView reload, the previous picture still in loading, and a same imageUrl was set to it, SD will cancel current operation and restart a new one to load this picture.
3. in Charles you can see below case


it is called by

- (void)sd_cancelImageLoadOperationWithKey:(nullable NSString *)key {
    if (key) {
        // Cancel in progress downloader from queue
        SDOperationsDictionary *operationDictionary = [self sd_operationDictionary];
        id<SDWebImageOperation> operation;
        
        @synchronized (self) {
            operation = [operationDictionary objectForKey:key];
        }
        if (operation) {
            if ([operation conformsToProtocol:@protocol(SDWebImageOperation)]) {
                [operation cancel];
                printf(@"@#@ - cancel");
            }
            @synchronized (self) {
                [operationDictionary removeObjectForKey:key];
            }
        }
    }
}

I can understand it could be used for load different pictures, but for same pictures I think it is better to avoid duplicated loading, it will delay the customer see the image.

Please help correct me, if there is something I misunderstand, thanks.