%SYS.Audit already projects to each namespace, but the data is in a privileged database and requires %Admin_Secure:USE privileges, so better not try to circumvent / confuse that through mappings.

I would not create additional temp tables or mappings to try and cling to SQL as that is meant to run in a single namespace as a query language. This sounds more like a procedural thing for ObjectScript, so a stored procedure that loops through the Production namespaces, retrieves all config items in a local variable and then uses that for querying the audit table after switching to %SYS sounds more appropriate. Rather than a PPG, I'd just collect it in the qHandle local variable passed between Execute() and Fetch() methods for your custom query, unless it risks getting too big

Can you provide a little more context on what your subqueries are trying to accomplish? Conceptually, it feels a little unnatural to force PID awareness into SQL (sub)queries, so maybe this is more an application scenario asking for more direct interaction with the Work Queue Manager. 

In 2022.2, we introduced an Application Metadata Stack that SQL (and in the future other subsystems or application code) uses to stash a little context in the process metadata in order to build things like the SQL Process View. Amongst other things, that metadata helps us tie subquery processes to their parent. Right now we have no public API to interpret this rather technical metadata directly from the stack, but maybe you can convince us there's a use case :-)

Nice visionary article!

Luckily we didn't rush this 13 years ago ;-) as the model described in there would offer some benefits, but not get to the order of magnitude performance improvement we're bringing with this new IRIS feature. Organizing data in separate nodes as proposed there may help somewhat to limit the size of each read (read the column value rather than the full row's $list), but you're still doing NxM small grefs to read M columns for N rows. When you're talking billions of rows, that sheer volume of grefs is the bottleneck we saw preventing us from doing really well on analytics queries. 

With Columnar Storage, the new $vector datatype we introduced that encodes 64k values into a single global node offers much better economies on today's hardware, and also enable SIMD instructions on those, which you couldn't get by keeping values in separate variables. Of course introducing all-new datatypes (and especially internal ones like $vector) isn't something you could do using ObjectScript in user code, but I promise we'll offer Key-Value before IRIS 2036.1! :-)

They're on the WRC preview distribution page and I see enterprise edition ARM64 containers on ICR after logging in. We'll check why the CE containers are not (yet) on ICR for this build.

FWIW, Abstract classes inheriting from %Persistent (or even %SerialObject) do have a storage definition and can define indices too. They just can't be instantiated. To prevent the creation of a storage definition, NoExtent is the keyword to use.

For the record: it's not the Abstract-ness that leads to the index being ignored, it's the fact that the index is not defined in the primary superclass of Test.NewClass1. From secondary superclasses, only parameters, properties and methods are inherited, but not indices. So you can keep Test.NewClass Abstract, but make it inherit from %Persistent itself and then have Test.NewClass1 point to it as its primary superclass. I'll ask the doc team to make this a little clearer, as it's not obvious from this section of the doc nor the one on indices right now.

This said, @Robert Cemper 's suggested use of NoExtent is likely what you wanted to achieve.

Yes, it always behaved like this. Currently, table stats are stored as part of the class definition, based on the idea that they are often kind of static and belong with the application. That holds for certain types of applications, but in many cases it is a little too static and this is especially true for the Message Bank example here, as TuneTable cannot update class definitions for a read-only system class.

We have a project coming up to move the table stats to live with the data rather than keep them in the class definition and hope to bring that to an IRIS release in the course of 2023. In the meantime, the workaround suggested above, marking ENSLIB as writable, running TT and then marking it read-only again is reasonable (though quite a step from an official recommendation). Note that after upgrades, your ENSLIB will be overwritten and your stats will have been lost.

FYI, the last part of this article also touches on this subject