Performance on using hierarchical tasks in a huge task list

Question

We combined multiple task lists into one to overcome different difficulties. This resulted in a task list with about 90.000 items. Upon opening a hierarchical task view with an additional filter on an indexed column, SharePoint takes about 60s to render the page. The time consuming operations seem to reside on the server side, as we get our first response inside the network tab of FireBug at about 58s. We think, SharePoint will be getting all list items to sort them properly into the hierarchy.

Does anybody have a clue if SharePoint could be convinced to just load those elements, that would be contained inside the filter? Upon filtering directly or by using a view grouped by the filter element, the page renders in about 2 seconds.

Answer 1

We cannot change SharePoint’s behavior on rending data in a list. “The time-consuming operations”, as you mentioned, is the filtered views with column indexes (and other operations) creating database queries and retrieving data returned.

You can see the section "What happens behind the scenes when you access many items in a list or library?" in this document: Manage large lists and libraries.

Accordingly, the Group By feature and direct filtering should render first, as a valid method to avoid List View Threshold error and related performance issues. Then the hierarchical tasks load all items in a nested structure, which shows in an expanded view by default.