Catalog generation: Work on a copy of the library database so as not to lock it

src/calibre/gui2/convert/gui_conversion.py

@@ -30,7 +30,7 @@ def gui_catalog(fmt, title, dbspec, ids, out_file_name, sync, fmt_options, conne
     from calibre.library import db
     from calibre.utils.config import prefs
     prefs.refresh()
-    db = db()
+    db = db(read_only=True)
     db.catalog_plugin_on_device_temp_mapping = dbspec
 
     # Create a minimal OptionParser that we can append to

src/calibre/library/__init__.py

@@ -2,10 +2,11 @@ __license__   = 'GPL v3'
 __copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 ''' Code to manage ebook library'''
 
-def db(path=None):
+def db(path=None, read_only=False):
     from calibre.library.database2 import LibraryDatabase2
     from calibre.utils.config import prefs
-    return LibraryDatabase2(path if path else prefs['library_path'])
+    return LibraryDatabase2(path if path else prefs['library_path'],
+            read_only=read_only)
 
 
 def generate_test_db(library_path, # {{{

src/calibre/library/database2.py

@@ -113,7 +113,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
     def exists_at(cls, path):
         return path and os.path.exists(os.path.join(path, 'metadata.db'))
 
-    def __init__(self, library_path, row_factory=False, default_prefs=None):
+    def __init__(self, library_path, row_factory=False, default_prefs=None,
+            read_only=False):
         self.field_metadata = FieldMetadata()
         self.dirtied_queue = Queue()
         if not os.path.exists(library_path):
@@ -124,6 +125,12 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
         self.dbpath = os.path.join(library_path, 'metadata.db')
         self.dbpath = os.environ.get('CALIBRE_OVERRIDE_DATABASE_PATH',
                 self.dbpath)
+        if read_only and os.path.exists(self.dbpath):
+            pt = PersistentTemporaryFile('_ro.db')
+            pt.close()
+            shutil.copyfile(self.dbpath, pt.name)
+            self.dbpath = pt.name
+
         if isinstance(self.dbpath, unicode) and not iswindows:
             self.dbpath = self.dbpath.encode(filesystem_encoding)