Swift 5 UISearchController Firebase数据库非常慢/缓慢

Question

使用UISearchController搜索包含Firebase数据的UITableView较慢/慢，表中的单元格更多。我尝试观察单个事件，而不是连续观察数据库，但这并没有任何改变。

我在这里遵循了Ray Wenderlich的指南：https://www.raywenderlich.com/472-uisearchcontroller-tutorial-getting-started

下载的示例代码不会滞后。我不知道为什么我的这么慢。例如，点击搜索栏需要1-2秒才能加载。

这是我的一些代码： 搜索控制器：

extension SubCategoryViewController: UISearchResultsUpdating {
func updateSearchResults(for searchController: UISearchController){
    filterContentForSearchText(searchController.searchBar.text!)
 }
}

 override func viewDidLoad() {
    super.viewDidLoad()
    searchBarSetup()
 ....
 }

let searchController = UISearchController(searchResultsController: nil)
var filtered = [SubCategoryCellInfo]()

func searchBarIsEmpty() -> Bool {
    return searchController.searchBar.text?.isEmpty ?? true
}
func filterContentForSearchText(_ searchText: String) {
    filtered = subCategories.filter({( cellInfo : SubCategoryCellInfo) -> Bool in
        return cellInfo.itemBrand!.lowercased().contains(searchText.lowercased())
    })
    subCategoryTable.reloadData()
}
func isFiltering() -> Bool {
    return searchController.isActive && !searchBarIsEmpty()
}

func searchBarSetup() {

    navigationItem.searchController = searchController
    navigationItem.hidesSearchBarWhenScrolling = false

    searchController.searchResultsUpdater = self
    searchController.obscuresBackgroundDuringPresentation = false
    searchController.searchBar.placeholder = "Search"
    navigationItem.searchController = searchController
    definesPresentationContext = true
}