get_id_from_uuid()

src/calibre/db/cache.py

@@ -1353,6 +1353,11 @@ def set_link_for_authors(self, author_id_to_link_map):
         self._mark_as_dirty(changed_books)
         return changed_books
 
+    @read_api
+    def lookup_by_uuid(self, uuid):
+        return self.fields['uuid'].table.lookup_by_uuid(uuid)
+
+
     # }}}
 
 class SortKey(object):  # {{{

src/calibre/db/legacy.py

@@ -153,6 +153,10 @@ def field_id_map(self, field):
     def refresh(self, field=None, ascending=True):
         self.data.refresh(field=field, ascending=ascending)
 
+    def get_id_from_uuid(self, uuid):
+        if uuid:
+            return self.new_api.lookup_by_uuid(uuid)
+
     def add_listener(self, listener):
         '''
         Add a listener. Will be called on change events with two arguments.

src/calibre/db/tables.py

@@ -137,6 +137,9 @@ def remove_books(self, book_ids, db):
                 clean.add(val)
         return clean
 
+    def lookup_by_uuid(self, uuid):
+        return self.uuid_to_id_map.get(uuid, None)
+
 class CompositeTable(OneToOneTable):
 
     def read(self, db):

src/calibre/db/tests/legacy.py

@@ -163,6 +163,7 @@ def test_legacy_direct(self):  # {{{
 
         for meth, args in {
             'get_next_series_num_for': [('A Series One',)],
+            'get_id_from_uuid':[('ddddd',), (db.uuid(1, True),)],
             'get_author_id': [('author one',), ('unknown',), ('xxxxx',)],
             'series_id': [(0,), (1,), (2,)],
             'publisher_id': [(0,), (1,), (2,)],