It's weird that your extent size is showing up as 3521840 but your SELECT COUNT(*) says 49468

Maybe you need to rebuild pxfactidIndex?

I think the difference in relative costs makes sense. In the "WHERE pxfactid IS NULL" query, you are only looping over a specific subsection of the global. This is similar if you have a query that says SELECT COUNT(*) FROM SomeTable WHERE pxfactid  = 'hello'

In the second query, you are not looping over subrange of nodes that have a specific value, instead you are looping over the entirety of the index and testing whether its content do not match null. This is equivalent to SELECT COUNT(*) FROM SomeTable WHERE pxfactid  != 'hello'

Hi Anthony,

Preparation material are listed in the exam page of each exam. You can find the list of exam pages here.

Let's say for example that you are taking the InterSystems HL7 Interface Specialist, then a list of applicable preparation material are found in this page, under the heading "Recommended Preparation".