论如何搞定置顶会自动掉下去的问题

其实这是上游写的一个Feature...不过，对于随时会更改的导航贴，这样做显然不是十分妥当。
这论坛的问题已经搞定了，就借上游坛的图加以说明了：

可以看到，置顶已读后会自己掉下去。
我在上游坛找了找，发现了一个解决方案：

然后我就照着这个改了代码。但事实上，这样做会使得第一页加载更多时无限加载置顶。像这样：

我就很头疼了。
不过，读一下这一段代码，不难发现Toby在注释里说明了下面这一段是检测已读状态的：

            // If we are viewing a specific tag, then pin all stickied
            // discussions to the top no matter what.
            $gambits = $search->getActiveGambits();
            if ($count = count($gambits)) {
                if ($count === 1 && $gambits[0] instanceof TagGambit) {
                    if (! is_array($query->orders)) {
                        $query->orders = [];
                    }
                    array_unshift($query->orders, ['column' => 'is_sticky', 'direction' => 'desc']);
                }
                return;
            }
            // Otherwise, if we are viewing "all discussions", only pin stickied
            // discussions to the top if they are unread. To do this in a
            // performant way we create another query which will select all
            // stickied discussions, marry them into the main query, and then
            // reorder the unread ones up to the top.
            $sticky = clone $query;
            $sticky->where('is_sticky', true);
            $sticky->orders = null;
            
            $query->union($sticky);
            
            $read = $query->newQuery()
                ->selectRaw(1)
                ->from('discussion_user as sticky')
                ->whereColumn('sticky.discussion_id', 'id')
                ->where('sticky.user_id', '=', $search->getActor()->id)
                ->whereColumn('sticky.last_read_post_number', '>=', 'last_post_number');
            // Add the bindings manually (rather than as the second
            // argument in orderByRaw) for now due to a bug in Laravel which
            // would add the bindings in the wrong order.
            $query->orderByRaw('is_sticky and not exists ('.$read->toSql().') and last_posted_at > ? desc')
                ->addBinding(array_merge($read->getBindings(), [$search->getActor()->read_time ?: 0]), 'union');
            $query->unionOrders = array_merge($query->unionOrders, $query->orders);
            $query->unionLimit = $query->limit;
            $query->unionOffset = $query->offset;
            $query->limit = $sticky->limit = $query->offset + $query->limit;
            $query->offset = $sticky->offset = null;
        }
    }
}

于是我就从75行开始删，同时照着上面的方法囊括前面判定列表顺序的if一起照前人方法替换成了这样：

            // If we are viewing a specific tag, then pin all stickied
            // discussions to the top no matter what.
            $gambits = $search->getActiveGambits();
            if ($count = count($gambits)) {
                if ($count === 1 && $gambits[0] instanceof TagGambit) {
                    if (! is_array($query->orders)) {
                        $query->orders = [];
                    }
                    array_unshift($query->orders, ['column' => 'is_sticky', 'direction' => 'desc']);
                }
                return;
            }
            // Otherwise, if we are viewing "all discussions", only pin stickied
            // discussions to the top if they are unread. To do this in a
            // performant way we create another query which will select all
            // stickied discussions, marry them into the main query, and then
            // reorder the unread ones up to the top.
            $sticky = clone $query;
            $sticky->where('is_sticky', true);
            $sticky->orders = null;
            
             if (! is_array($query->orders)) {
                        $query->orders = [];
                    }
             array_unshift($query->orders, ['column' => 'is_sticky', 'direction' => 'desc']);
        }
    }
}

然后就完美地解决了这个问题，虽然我一点也不会PHP，对于原理我也没搞懂