If you have more recent versions of Cache you will likely benefit by using %PARALLEL especially if you have a large number of cores for your environment.

Might it be simpler to just use the sql function GREATEST.

While not specifically an answer to your question I have used Class Projections  as a way to detect when a class is compiled or removed.  This will not allow you to see the changes between classes but could be useful to see when classes are compiled.

Given that you guys have opened the hood, while not specifically a DOCBOOK request, I would like to see https://www.chromium.org/tab-to-search be supported for DOCBBOOK content.  As an example I'd like to when using Google Chrome be able to type 

docs.intersystems.com [tab] {SearchTerm} 

 and have the page respond with a list of results based on {SearchTerm}

I understand there may be issues with what version of DOCBOOK to show but it might be useful to just show results from the latest version.

Just checking as I still see Technical Articles I assume if you add content to DOCBOOK this additional content will still be part of this new UI?

One aspect that has been lost in the transition is to have the Search Dialog always on the page.  If you go to this page as an example http://docs.intersystems.com/beta/csp/docbook/DocBook.UI.FramePage.cls?K... in order to initiate a new search it appears I have to

1. Select this back button on the top left hand corner 
2. Scroll the left hand side menu, list of books to the very top
3. Place my cursor in the search field and enter a new search term.

Whereas in the old system I could 

1. Press the [Home] key to be taken to the top
2. Enter a new search term.

I would vote to make the search box visible at all times.

If you can share the Show Plan information for each query that will probably add some insight.   Given that the second query has only one column it may be that there are additional adjustments to the query that would yield better performance, although this does not directly address your specific question as to why it is much slower.  At the same time a query that is taking well over 30 minutes seems like there is something not quite right.

Great news.

only comment I would add is I would think the peformance chart in this article would be easier to quickly digest if all of the values were in ms.