Thanks for your kind comments.
I am a bit surprised that this happens in the first place (meaning that Apple haven't found a way to avoid this)
The question is why does it happen? There are any number of reasons why it might.
that there is not a simple command in the menu to start the cache build up,
There is a simple command:
Apple plus command and reopened i Photo.
That's it.
This sound lie your db is damaged.
Download
iPhoto Library Manager and use its rebuild function. This will create a new library based on data in the albumdata.xml file. Not everything will be brought over - no slideshows, books or calendars, for instance - but it should get all your albums and keywords back.
Because this process creates an entirely new library and leaves your old one untouched, it is non-destructive, and if you're not happy with the results you can simply return to your old one.
Regards
TD