From 51989627635cdb9b4ae957db349e00fad7d4d911 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Sun, 9 Nov 2014 21:38:23 +0530
Subject: [PATCH] ...

---
 src/calibre/db/cache.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/calibre/db/cache.py b/src/calibre/db/cache.py
index eaa4bfd718..11ce1de526 100644
--- a/src/calibre/db/cache.py
+++ b/src/calibre/db/cache.py
@@ -1427,7 +1427,7 @@ class Cache(object):
         ''' Return data suitable for use in :meth:`has_book`. This can be used for an
         implementation of :meth:`has_book` in a worker process without access to the
         db. '''
-        return {icu_lower(title):book_id for book_id, title in self.fields['title'].table.book_col_map.itervalues()}
+        return {icu_lower(title) for title in self.fields['title'].table.book_col_map.itervalues()}
 
     @read_api
     def has_book(self, mi):