Start work on legacy custom column API

src/calibre/db/backend.py

@@ -549,6 +549,7 @@ class DB(object):
 
         # Load metadata for custom columns
         self.custom_column_label_map, self.custom_column_num_map = {}, {}
+        self.custom_column_num_to_label_map = {}
         triggers = []
         remove = []
         custom_tables = self.custom_tables
@@ -586,6 +587,7 @@ class DB(object):
 
             self.custom_column_num_map[data['num']] = \
                 self.custom_column_label_map[data['label']] = data
+            self.custom_column_num_to_label_map[data['num']] = data['label']
 
             # Create Foreign Key triggers
             if data['normalized']:
@@ -785,6 +787,11 @@ class DB(object):
                 self._conn = Connection(self.dbpath)
         return self._conn
 
+    def custom_field_name(self, label=None, num=None):
+        if label is not None:
+            return self.field_metadata.custom_field_prefix + label
+        return self.field_metadata.custom_field_prefix + self.custom_column_num_to_label_map[num]
+
     def close(self):
         if self._conn is not None:
             self._conn.close()

src/calibre/db/legacy.py

@@ -70,6 +70,7 @@ class LibraryDatabase(object):
             setattr(self, x, getattr(self.data, x))
 
         self.is_case_sensitive = getattr(backend, 'is_case_sensitive', False)
+        self.custom_field_name = backend.custom_field_name
 
         self.last_update_check = self.last_modified()
 
@@ -638,6 +639,7 @@ for field in ('authors', 'tags', 'publisher', 'series'):
     name = field[:-1] if field in {'authors', 'tags'} else field
     setattr(LibraryDatabase, 'all_%s_names' % name, MT(getter(field)))
 LibraryDatabase.all_formats = MT(lambda self:self.new_api.all_field_names('formats'))
+LibraryDatabase.all_custom = MT(lambda self, label=None, num=None:self.new_api.all_field_names(self.custom_field_name(label, num)))
 
 for func, field in {'all_authors':'authors', 'all_titles':'title', 'all_tags2':'tags', 'all_series':'series', 'all_publishers':'publisher'}.iteritems():
     def getter(field):

src/calibre/db/tests/legacy.py

@@ -604,7 +604,17 @@ class LegacyTest(BaseTest):
         ))
         db.close()
 
-
-
+    # }}}
+
+    def test_legacy_custom(self):  # {{{
+        'Test the legacy API for custom columns'
+        ndb = self.init_legacy(self.cloned_library)
+        db = self.init_old(self.cloned_library)
+        run_funcs(self, db, ndb, (
+            ('all_custom', 'series'),
+            ('all_custom', 'tags'),
+            ('all_custom', 'rating'),
+            ('all_custom', 'authors'),
+        ))
     # }}}