I see that this change is listed in the WIKI, but it still is causing errors for me. Perhaps my upgrade wasn't as successful as it reported to be.
This change should still allow to add a module to a page, right? Mine doesn't. I can add the module if I add the TabPath column back to the TABS table.
Changes to Tab Hierarchy Management»
DotNetNuke 6.2.0 introduces changes to how the Tab (Page) Hierarchy is managed. Due to the limitations of earlier versions of SQL Server, prior to these changes, the business layer managed the handling of the tab hierarchy. Whenever a tab was created or moved in the hierarchy, there was a lot of calculation to calculate the effect on other tabs and update them accordingly.
In a large site like this one - if a tab with a large number of descendants is updated then every descendant is updated so that its "Level" and "TabPath" can be updated in the database.
SQL Server 2005 introduced the concept of "Common Table Expressions" or CTEs, which allow you to create recursive SQL scripts with fairly decent performance. Since we now require at least SQL Server 2005 as our base version of SQL Server, we have removed the Level and TabPath columns from the Tabs table and instead calculate them "on-the-fly" in the Tabs View.
This, in turn means that we don't have to do all the manipulation in the business layer in order to manage these properties.
In addition, we pushed more of the logic for creating and moving tabs into more explicit stored procedures e.g. MoveTabBefore, MoveTabAfter etc. A few methods in TabController that are no longer necessary have been deprecated and a few new ones created.
To give an example of the effect of these changes - consider a tab with 20 child tabs. To move one of those child tabs (in the Page Management module) to the top triggered 166 calls to the database in 6.1.2. In 6.2.0 this move triggers 5 calls to the database, and the guts of the work is done in a single stored procedure MoveTabBefore.
For the most part this change does not affect 3rd party developers unless they are manipulating pages, but the performance (and reliability) of moving tabs is now enhanced significantly.