Large Calibre Library Slow - Solved

[Mythlandia]

With my very large Calibre library it was taking much to long to open Calibre (over ten minutes) and to do updates. I thought I had done all the suggested options, but found that I had defined custom columns in the "Add your own columns" under "Preferences".
Once I had removed the columns (as opposed to merely unchecking them) Calibre opened in about 30 seconds. With the other excellent database backend improvements particularly with the backend, saved searches, and virtual libraries (and hiding the tag browser unless I really need it), Calibre is now responsive with most operations taking a second or two.