Poor performance with large library

I have not been using calibre for a while, but since maybe version 3.2, the database performance has severely degraded with large databases.

Previously, the size of the database did not seem to be important, but now I have to wait 5 minutes or more for a single change.

OK, we have a ridiculous large database, over 30000 entries.

I am running calibre 3.7, on a Core i7 laptop with plenty memory, The database resides on a file server with a Gb ethernet connection.

With an (almost) empty database, performance is excellent.

Of course I am willing to provide more info if requested.

TIA,

Bart