Here is a snippet that I learned yesterday You can define an index on a collection property but when I tried to use it, I failed. I was using
Select ….. where …. :xx %INLIST collproperty
But this will not use an index, but the equivalent syntax
SELECT .. WHERE ... FOR SOME %ELEMENT(collproperty) (%VALUE=:xx)
will use the index  Check out      http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=RSQL_forsomeelement   Dave