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.

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?… 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.

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?

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.

While the cost may be high, the real question might be better focused on the performance.  Relative cost is just that, relative. 

What does the rest of the query look like?

What is the time to first row, time for all of the data? 

Does the query plan utilize the index on the StartDate column?

I'm generally looking at the query plans either from the SMP or from the context menu in Studio while writing class queries/embedded sql statements.

One issue that I've seen is that while the query plan is very good, an in many cases better than what other dbms's provide, when a sub-query is part of your query statement it's not exactly clear when it is utilized in the query plan.  For example, I have this query plan

I cannot tell with 100% certainty where "subquery" is called.

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.

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.

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

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.

A couple ideas

If it's for debugging I use $System .OBJ.Dump(oRef)

If it's in application code I ran across something that looked like

While prop '= "" {
//  Use global lookup instead of %Dictionary.Class query so users don't need privileges on that table
Set tPropClass = $$$comMemberKeyGet(sourceClass,$$$cCLASSproperty,prop,$$$cPROPtype)
 

I would be interested in the English version as well.

Depending on what you exactly mean by the same structure you consider using a Serial Class definition that is embedded in both of your classes.  However, if the structure is stored across several global nodes I do not think you could use this as the Serial class would define the pieces(whether delimited or $ListBuild pieces) and then the serial property is described in your 2 classes to occupy a single node.

You could also consider defining a single abstract class that describes the properties and have your 2 classes inherit from your abstract class.

With regards to having a variable defining the data location I suspect that it may not be doable, even if it were I don't see how it improves things in a significant way.

You wrote

BUT the server is 6 times faster if OpenId replaced with simple read of a large global (s p=^someLargeGlobal). Any ideas what makes OpenId so slow only on the server?

while not specifically answering your general question, note that opening an object is very different than 

Set p=^SomeLargeGlobal.

When you call %OpenId

1. Concurrency is checked.  While not widely used there is a second parameter to the %OpenId method that controls the behavior of concurrency  and you may want to consider providing the desired concurrency option.  In the past if I was not concerned with concurrency as I just wanted to read data I would use option 0.
2. Each and every property defined in your class is loaded into memory, ie the data is read from the global and then the individual properties are set accordingly.  Depending on how complex your class is the difference between 

Set p=^SomeLargeGlobal 

and %OpenId can be quite different, at least academically.

If your class as relationships and/or serial/embedded classes I do not believe those properties are fully loaded into memory, but I could be incorrect.

In practice, if I need an object I use objects, if I need only a small part of the object/row I'll use embedded SQL for better performance.

Again this does not specifically answer your general question but I think it is useful to understand what %OpenId does and why it's not the same as 

Set p=^SomeLargeGlobal.

I used to work at IDX under the division that produced what was called IDX Flowcast.  IDX Flowcast is a practice management system for large practice/academic medical centers.  Groupcast on the other hand was for the small practice environment, I don't recall the exact # of doctors as the threshold cutoff.  I do not believe Groupcast is based on Intersystems Cache, but I could be incorrect.  If the system is Flowcast aka GE Centricity Business, then most all of the data is exposed via Cache classes that are based on %SQLStorage and hence would be exposed via any SQL client interface connecting to Flowcast/GE Centricity Business using ODBC/JDBC.

Some of the reasons why I focus on utilizing class queries include

• Studio and other editors are much better at providing coloring/syntax checking vs a strategy of setting a tSQL string as some arbitrary SQL statement
• As mentioned in the original post it provides the separation that allows for easy re-use and testing.  If I have a class query I can decide to allow it to be reflected as a stored procedure, I can expose it to ZEN reports, ODBC/JDBC, JSON projection, %XML.DataSet, I can use it to satisfy a control in ZEN that allows for binding to a class query,  as well as others.  Basically, it provides for great separation.
• I also like the idea of considering writing the statement using SQL as %Query.  If for some reason I run into performance issues that I cannot overcome I can change the implementation to %SQLQuery and implement COS code, the calling application would see the improved performance but does not have to understand the internal implementation.  However, I've only done this on extremely rare occasions.
• I think one of the most important aspects of SQL to always read the query plan, it's there where you can understand what the optimizer is going to do.  I care all about the query plan and almost always validate what it reports.  Having a class query allows for easy Show Plan examination whereas it's generally hard to do if you take the approach of setting a tSQL string(sometimes with concatenation over several lines).

Class Queries are really worth investing in IMHO.

The IDX system is oftentimes partitioned by Group(GRP).   Additionally I suspect the 86M records do not represent invoices for a single year.  Using %SYSTEM.WorkMgr you could break the job up in to smaller jobs by GRP and or InvCrePd or YEAR(BAR.Invoice.SerDt) 

This article refers to https://github.com/es-comunidad-intersystems/IRIS-in-Astronomy but when I tried going there you get a 404 Page not found.  Maybe the repo is not public?