diff --git a/src/calibre/devices/usbms/books.py b/src/calibre/devices/usbms/books.py
index cfebe796a3..731d3e2b49 100644
--- a/src/calibre/devices/usbms/books.py
+++ b/src/calibre/devices/usbms/books.py
@@ -204,7 +204,8 @@ class CollectionsBookList(BookList):
                 elif fm['datatype'] == 'text' and fm['is_multiple']:
                     val = orig_val
                 elif fm['datatype'] == 'composite' and fm['is_multiple']:
-                    val = [v.strip() for v in val.split(fm['is_multiple'])]
+                    val = [v.strip() for v in
+                           val.split(fm['is_multiple']['ui_to_list'])]
                 else:
                     val = [val]
 
diff --git a/src/calibre/ebooks/metadata/opf2.py b/src/calibre/ebooks/metadata/opf2.py
index 1d91236757..b83e0f5177 100644
--- a/src/calibre/ebooks/metadata/opf2.py
+++ b/src/calibre/ebooks/metadata/opf2.py
@@ -7,7 +7,7 @@ __docformat__ = 'restructuredtext en'
 lxml based OPF parser.
 '''
 
-import re, sys, unittest, functools, os, uuid, glob, cStringIO, json
+import re, sys, unittest, functools, os, uuid, glob, cStringIO, json, copy
 from urllib import unquote
 from urlparse import urlparse
 
@@ -457,6 +457,14 @@ def serialize_user_metadata(metadata_elem, all_user_metadata, tail='\n'+(' '*8))
 
     for name, fm in all_user_metadata.items():
         try:
+            if fm.get('is_multiple'):
+                # migrate is_multiple back to a character
+                fm = copy.copy(fm)
+                dt = fm.get('datatype', None)
+                if dt == 'composite':
+                    fm['is_multiple'] = ','
+                else:
+                    fm['is_multiple'] =  '|'
             fm = object_to_unicode(fm)
             fm = json.dumps(fm, default=to_json, ensure_ascii=False)
         except:
@@ -585,6 +593,17 @@ class OPF(object): # {{{
             fm = elem.get('content')
             try:
                 fm = json.loads(fm, object_hook=from_json)
+                im = fm.get('is_multiple', None)
+                if im and not isinstance(im, dict):
+                    # Must migrate the is_multiple from char to dict
+                    dt = fm.get('datatype', None)
+                    if dt == 'composite':
+                        im = {'cache_to_list': ',', 'ui_to_list': ',', 'list_to_ui': ', '}
+                    elif fm.get('display', {}).get('is_names', False):
+                        im = {'cache_to_list': '|', 'ui_to_list': '&', 'list_to_ui': ', '}
+                    else:
+                        im = {'cache_to_list': '|', 'ui_to_list': ',', 'list_to_ui': ', '}
+                    fm['is_multiple'] = im
                 temp.set_user_metadata(name, fm)
             except:
                 prints('Failed to read user metadata:', name)
diff --git a/src/calibre/gui2/custom_column_widgets.py b/src/calibre/gui2/custom_column_widgets.py
index c94913ea2c..4706cce4c9 100644
--- a/src/calibre/gui2/custom_column_widgets.py
+++ b/src/calibre/gui2/custom_column_widgets.py
@@ -226,16 +226,14 @@ class Comments(Base):
 class Text(Base):
 
     def setup_ui(self, parent):
-        if self.col_metadata['display'].get('is_names', False):
-            self.sep = u' & '
-        else:
-            self.sep = u', '
+        self.sep = self.col_metadata['multiple_seps']
         values = self.all_values = list(self.db.all_custom(num=self.col_id))
         values.sort(key=sort_key)
+
         if self.col_metadata['is_multiple']:
             w = MultiCompleteLineEdit(parent)
-            w.set_separator(self.sep.strip())
-            if self.sep == u' & ':
+            w.set_separator(self.sep['ui_to_list'])
+            if self.sep['ui_to_list'] == '&':
                 w.set_space_before_sep(True)
                 w.set_add_separator(tweaks['authors_completer_append_separator'])
             w.update_items_cache(values)
@@ -269,12 +267,12 @@ class Text(Base):
         if self.col_metadata['is_multiple']:
             if not val:
                 val = []
-            self.widgets[1].setText(self.sep.join(val))
+            self.widgets[1].setText(self.sep['list_to_ui'].join(val))
 
     def getter(self):
         if self.col_metadata['is_multiple']:
             val = unicode(self.widgets[1].text()).strip()
-            ans = [x.strip() for x in val.split(self.sep.strip()) if x.strip()]
+            ans = [x.strip() for x in val.split(self.sep['ui_to_list']) if x.strip()]
             if not ans:
                 ans = None
             return ans
@@ -899,9 +897,10 @@ class BulkText(BulkBase):
         if not self.a_c_checkbox.isChecked():
             return
         if self.col_metadata['is_multiple']:
+            ism = self.col_metadata['multiple_seps']
             if self.col_metadata['display'].get('is_names', False):
                 val = self.gui_val
-                add = [v.strip() for v in val.split('&') if v.strip()]
+                add = [v.strip() for v in val.split(ism['ui_to_list']) if v.strip()]
                 self.db.set_custom_bulk(book_ids, add, num=self.col_id)
             else:
                 remove_all, adding, rtext = self.gui_val
@@ -911,10 +910,10 @@ class BulkText(BulkBase):
                 else:
                     txt = rtext
                     if txt:
-                        remove = set([v.strip() for v in txt.split(',')])
+                        remove = set([v.strip() for v in txt.split(ism['ui_to_list'])])
                 txt = adding
                 if txt:
-                    add = set([v.strip() for v in txt.split(',')])
+                    add = set([v.strip() for v in txt.split(ism['ui_to_list'])])
                 else:
                     add = set()
                 self.db.set_custom_bulk_multiple(book_ids, add=add,
diff --git a/src/calibre/gui2/dialogs/metadata_bulk.py b/src/calibre/gui2/dialogs/metadata_bulk.py
index 66cf55a9b2..a6f7ed8843 100644
--- a/src/calibre/gui2/dialogs/metadata_bulk.py
+++ b/src/calibre/gui2/dialogs/metadata_bulk.py
@@ -520,7 +520,7 @@ class MetadataBulkDialog(ResizableDialog, Ui_MetadataBulkDialog):
             elif not fm['is_multiple']:
                 val = [val]
             elif fm['datatype'] == 'composite':
-                val = [v.strip() for v in val.split(fm['is_multiple'])]
+                val = [v.strip() for v in val.split(fm['is_multiple']['ui_to_list'])]
             elif field == 'authors':
                 val = [v.replace('|', ',') for v in val]
         else:
@@ -655,14 +655,14 @@ class MetadataBulkDialog(ResizableDialog, Ui_MetadataBulkDialog):
 
         if self.destination_field_fm['is_multiple']:
             if self.comma_separated.isChecked():
-                if dest == 'authors' or \
-                        (self.destination_field_fm['is_custom'] and
-                         self.destination_field_fm['datatype'] == 'text' and
-                         self.destination_field_fm['display'].get('is_names', False)):
-                    splitter = ' & '
-                else:
-                    splitter = ','
-
+                splitter = self.destination_field_fm['is_multiple']['ui_to_list']
+#                if dest == 'authors' or \
+#                        (self.destination_field_fm['is_custom'] and
+#                         self.destination_field_fm['datatype'] == 'text' and
+#                         self.destination_field_fm['display'].get('is_names', False)):
+#                    splitter = ' & '
+#                else:
+#                    splitter = ','
                 res = []
                 for v in val:
                     for x in v.split(splitter):
diff --git a/src/calibre/gui2/library/models.py b/src/calibre/gui2/library/models.py
index 72c8e0629f..72655afd12 100644
--- a/src/calibre/gui2/library/models.py
+++ b/src/calibre/gui2/library/models.py
@@ -608,10 +608,11 @@ class BooksModel(QAbstractTableModel): # {{{
 
         def text_type(r, mult=None, idx=-1):
             text = self.db.data[r][idx]
-            if text and mult is not None:
-                if mult:
-                    return QVariant(u' & '.join(text.split('|')))
-                return QVariant(u', '.join(sorted(text.split('|'),key=sort_key)))
+            if text and mult:
+                jv = mult['list_to_ui']
+                sv = mult['cache_to_list']
+                return QVariant(jv.join(
+                    sorted([t.strip() for t in text.split(sv)], key=sort_key)))
             return QVariant(text)
 
         def decorated_text_type(r, idx=-1):
@@ -665,8 +666,6 @@ class BooksModel(QAbstractTableModel): # {{{
             datatype = self.custom_columns[col]['datatype']
             if datatype in ('text', 'comments', 'composite', 'enumeration'):
                 mult=self.custom_columns[col]['is_multiple']
-                if mult is not None:
-                    mult = self.custom_columns[col]['display'].get('is_names', False)
                 self.dc[col] = functools.partial(text_type, idx=idx, mult=mult)
                 if datatype in ['text', 'composite', 'enumeration'] and not mult:
                     if self.custom_columns[col]['display'].get('use_decorations', False):
@@ -722,9 +721,9 @@ class BooksModel(QAbstractTableModel): # {{{
                 if id_ in self.color_cache:
                     if key in self.color_cache[id_]:
                         return self.color_cache[id_][key]
-                if mi is None:
-                    mi = self.db.get_metadata(id_, index_is_id=True)
                 try:
+                    if mi is None:
+                        mi = self.db.get_metadata(id_, index_is_id=True)
                     color = composite_formatter.safe_format(fmt, mi, '', mi)
                     if color in self.colors:
                         color = QColor(color)
diff --git a/src/calibre/gui2/preferences/coloring.py b/src/calibre/gui2/preferences/coloring.py
index 695adabed8..793d529c92 100644
--- a/src/calibre/gui2/preferences/coloring.py
+++ b/src/calibre/gui2/preferences/coloring.py
@@ -205,7 +205,7 @@ class ConditionEditor(QWidget): # {{{
                 tt = _('Enter a regular expression')
             elif m.get('is_multiple', False):
                 tt += '\n' + _('You can match multiple values by separating'
-                        ' them with %s')%m['is_multiple']
+                        ' them with %s')%m['is_multiple']['ui_to_list']
         self.value_box.setToolTip(tt)
         if action in ('is set', 'is not set', 'is true', 'is false',
                 'is undefined'):
diff --git a/src/calibre/gui2/preferences/create_custom_column.py b/src/calibre/gui2/preferences/create_custom_column.py
index 8eaa2dd7d9..d2f1786ab0 100644
--- a/src/calibre/gui2/preferences/create_custom_column.py
+++ b/src/calibre/gui2/preferences/create_custom_column.py
@@ -13,6 +13,9 @@ from calibre.gui2 import error_dialog
 
 class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
 
+    # Note: in this class, we are treating is_multiple as the boolean that
+    # custom_columns expects to find in its structure. It does not use the dict
+
     column_types = {
                     0:{'datatype':'text',
                         'text':_('Text, column shown in the tag browser'),
diff --git a/src/calibre/library/caches.py b/src/calibre/library/caches.py
index 470bbcdfa8..17bec7e0e8 100644
--- a/src/calibre/library/caches.py
+++ b/src/calibre/library/caches.py
@@ -509,7 +509,7 @@ class ResultCache(SearchQueryParser): # {{{
             valq_mkind, valq = self._matchkind(query)
 
         loc = self.field_metadata[location]['rec_index']
-        split_char = self.field_metadata[location]['is_multiple']
+        split_char = self.field_metadata[location]['is_multiple']['cache_to_list']
         for id_ in candidates:
             item = self._data[id_]
             if item is None:
@@ -665,7 +665,8 @@ class ResultCache(SearchQueryParser): # {{{
                 if fm['is_multiple'] and \
                         len(query) > 1 and query.startswith('#') and \
                         query[1:1] in '=<>!':
-                    vf = lambda item, loc=fm['rec_index'], ms=fm['is_multiple']:\
+                    vf = lambda item, loc=fm['rec_index'], \
+                                ms=fm['is_multiple']['cache_to_list']:\
                             len(item[loc].split(ms)) if item[loc] is not None else 0
                     return self.get_numeric_matches(location, query[1:],
                                                     candidates, val_func=vf)
@@ -703,7 +704,8 @@ class ResultCache(SearchQueryParser): # {{{
                             ['composite', 'text', 'comments', 'series', 'enumeration']:
                         exclude_fields.append(db_col[x])
                     col_datatype[db_col[x]] = self.field_metadata[x]['datatype']
-                    is_multiple_cols[db_col[x]] = self.field_metadata[x]['is_multiple']
+                    is_multiple_cols[db_col[x]] = \
+                        self.field_metadata[x]['is_multiple'].get('cache_to_list', None)
 
             try:
                 rating_query = int(query) * 2
@@ -1045,13 +1047,14 @@ class SortKeyGenerator(object):
 
             elif dt in ('text', 'comments', 'composite', 'enumeration'):
                 if val:
-                    sep = fm['is_multiple']
-                    if sep:
-                        if fm['display'].get('is_names', False):
-                            val = sep.join(
-                                [author_to_author_sort(v) for v in val.split(sep)])
+                    if fm['is_multiple']:
+                        jv = fm['is_multiple']['list_to_ui']
+                        sv = fm['is_multiple']['cache_to_list']
+                        if '&' in jv:
+                            val = jv.join(
+                                [author_to_author_sort(v) for v in val.split(sv)])
                         else:
-                            val = sep.join(sorted(val.split(sep),
+                            val = jv.join(sorted(val.split(sv),
                                               key=self.string_sort_key))
                 val = self.string_sort_key(val)
 
diff --git a/src/calibre/library/coloring.py b/src/calibre/library/coloring.py
index f458b9c04f..0009b4636a 100644
--- a/src/calibre/library/coloring.py
+++ b/src/calibre/library/coloring.py
@@ -88,7 +88,7 @@ class Rule(object): # {{{
         if dt in ('comments', 'series', 'text', 'enumeration', 'composite'):
             ism = m.get('is_multiple', False)
             if ism:
-                return self.multiple_condition(col, action, val, ',' if ism == '|' else ism)
+                return self.multiple_condition(col, action, val, ism['ui_to_list'])
             return self.text_condition(col, action, val)
 
     def identifiers_condition(self, col, action, val):
diff --git a/src/calibre/library/custom_columns.py b/src/calibre/library/custom_columns.py
index 187d718a39..00ecccc78e 100644
--- a/src/calibre/library/custom_columns.py
+++ b/src/calibre/library/custom_columns.py
@@ -78,6 +78,18 @@ class CustomColumns(object):
                     }
             if data['display'] is None:
                 data['display'] = {}
+            # set up the is_multiple separator dict
+            if data['is_multiple']:
+                if data['display'].get('is_names', False):
+                    seps = {'cache_to_list': '|', 'ui_to_list': '&', 'list_to_ui': ' & '}
+                elif data['datatype'] == 'composite':
+                    seps = {'cache_to_list': ',', 'ui_to_list': ',', 'list_to_ui': ', '}
+                else:
+                    seps = {'cache_to_list': '|', 'ui_to_list': ',', 'list_to_ui': ', '}
+            else:
+                seps = {}
+            data['multiple_seps'] = seps
+
             table, lt = self.custom_table_names(data['num'])
             if table not in custom_tables or (data['normalized'] and lt not in
                     custom_tables):
@@ -119,7 +131,7 @@ class CustomColumns(object):
                 if x is None:
                     return []
                 if isinstance(x, (str, unicode, bytes)):
-                    x = x.split('&' if d['display'].get('is_names', False) else',')
+                    x = x.split(d['multiple_seps']['ui_to_list'])
                 x = [y.strip() for y in x if y.strip()]
                 x = [y.decode(preferred_encoding, 'replace') if not isinstance(y,
                     unicode) else y for y in x]
@@ -181,10 +193,7 @@ class CustomColumns(object):
                 is_category = True
             else:
                 is_category = False
-            if v['is_multiple']:
-                is_m = ',' if v['datatype'] == 'composite' else '|'
-            else:
-                is_m = None
+            is_m = v['multiple_seps']
             tn = 'custom_column_{0}'.format(v['num'])
             self.field_metadata.add_custom_field(label=v['label'],
                     table=tn, column='value', datatype=v['datatype'],
@@ -200,7 +209,7 @@ class CustomColumns(object):
         row = self.data._data[idx] if index_is_id else self.data[idx]
         ans = row[self.FIELD_MAP[data['num']]]
         if data['is_multiple'] and data['datatype'] == 'text':
-            ans = ans.split('|') if ans else []
+            ans = ans.split(data['multiple_seps']['cache_to_list']) if ans else []
             if data['display'].get('sort_alpha', False):
                 ans.sort(cmp=lambda x,y:cmp(x.lower(), y.lower()))
         return ans
@@ -571,9 +580,17 @@ class CustomColumns(object):
             if data['normalized']:
                 query = '%s.value'
                 if data['is_multiple']:
-                    query = 'group_concat(%s.value, "|")'
-                    if not display.get('sort_alpha', False):
-                        query = 'sort_concat(link.id, %s.value)'
+#                    query = 'group_concat(%s.value, "{0}")'.format(
+#                                        data['multiple_seps']['cache_to_list'])
+#                    if not display.get('sort_alpha', False):
+                    if data['multiple_seps']['cache_to_list'] == '|':
+                        query = 'sortconcat_bar(link.id, %s.value)'
+                    elif data['multiple_seps']['cache_to_list'] == '&':
+                        query = 'sortconcat_amper(link.id, %s.value)'
+                    else:
+                        prints('WARNING: unknown value in multiple_seps',
+                               data['multiple_seps']['cache_to_list'])
+                        query = 'sortconcat_bar(link.id, %s.value)'
                 line = '''(SELECT {query} FROM {lt} AS link INNER JOIN
                     {table} ON(link.value={table}.id) WHERE link.book=books.id)
                     custom_{num}
diff --git a/src/calibre/library/database2.py b/src/calibre/library/database2.py
index 3a151166e7..9c4c3eb004 100644
--- a/src/calibre/library/database2.py
+++ b/src/calibre/library/database2.py
@@ -1250,7 +1250,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             dex = field['rec_index']
             for book in self.data.iterall():
                 if field['is_multiple']:
-                    vals = [v.strip() for v in book[dex].split(field['is_multiple'])
+                    vals = [v.strip() for v in
+                            book[dex].split(field['is_multiple']['cache_to_list'])
                             if v.strip()]
                     if id_ in vals:
                         ans.add(book[0])
@@ -1378,7 +1379,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
             tcategories[category] = {}
             # create a list of category/field_index for the books scan to use.
             # This saves iterating through field_metadata for each book
-            md.append((category, cat['rec_index'], cat['is_multiple'], False))
+            md.append((category, cat['rec_index'],
+                       cat['is_multiple'].get('cache_to_list', None), False))
 
         for category in tb_cats.iterkeys():
             cat = tb_cats[category]
@@ -1386,7 +1388,8 @@ class LibraryDatabase2(LibraryDatabase, SchemaUpgrade, CustomColumns):
                                 cat['display'].get('make_category', False):
                 tids[category] = {}
                 tcategories[category] = {}
-                md.append((category, cat['rec_index'], cat['is_multiple'],
+                md.append((category, cat['rec_index'],
+                           cat['is_multiple'].get('cache_to_list', None),
                            cat['datatype'] == 'composite'))
         #print 'end phase "collection":', time.clock() - last, 'seconds'
         #last = time.clock()
diff --git a/src/calibre/library/field_metadata.py b/src/calibre/library/field_metadata.py
index c884542241..231af23038 100644
--- a/src/calibre/library/field_metadata.py
+++ b/src/calibre/library/field_metadata.py
@@ -50,9 +50,16 @@ class FieldMetadata(dict):
 
     datatype: the type of information in the field. Valid values are listed in
     VALID_DATA_TYPES below.
-    is_multiple: valid for the text datatype. If None, the field is to be
-    treated as a single term. If not None, it contains a string, and the field
-    is assumed to contain a list of terms separated by that string
+    is_multiple: valid for the text datatype. If {}, the field is to be
+    treated as a single term. If not None, it contains a dict of the form
+            {'cache_to_list': ',',
+             'ui_to_list': ',',
+             'list_to_ui': ', '}
+    where the cache_to_list contains the character used to split the value in
+    the meta2 table, ui_to_list contains the character used to create a list
+    from a value shown in the ui (each resulting value must be strip()ed and
+    empty values removed), and list_to_ui contains the string used in join()
+    to create a displayable string from the list.
 
     kind == field: is a db field.
     kind == category: standard tag category that isn't a field. see news.
@@ -97,7 +104,9 @@ class FieldMetadata(dict):
                            'link_column':'author',
                            'category_sort':'sort',
                            'datatype':'text',
-                           'is_multiple':',',
+                           'is_multiple':{'cache_to_list': ',',
+                                          'ui_to_list': '&',
+                                          'list_to_ui': ' & '},
                            'kind':'field',
                            'name':_('Authors'),
                            'search_terms':['authors', 'author'],
@@ -109,7 +118,7 @@ class FieldMetadata(dict):
                            'link_column':'series',
                            'category_sort':'(title_sort(name))',
                            'datatype':'series',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Series'),
                            'search_terms':['series'],
@@ -119,7 +128,9 @@ class FieldMetadata(dict):
             ('formats',   {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':',',
+                           'is_multiple':{'cache_to_list': ',',
+                                          'ui_to_list': ',',
+                                          'list_to_ui': ', '},
                            'kind':'field',
                            'name':_('Formats'),
                            'search_terms':['formats', 'format'],
@@ -131,7 +142,7 @@ class FieldMetadata(dict):
                            'link_column':'publisher',
                            'category_sort':'name',
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Publishers'),
                            'search_terms':['publisher'],
@@ -143,7 +154,7 @@ class FieldMetadata(dict):
                            'link_column':'rating',
                            'category_sort':'rating',
                            'datatype':'rating',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Ratings'),
                            'search_terms':['rating'],
@@ -154,7 +165,7 @@ class FieldMetadata(dict):
                            'column':'name',
                            'category_sort':'name',
                            'datatype':None,
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'category',
                            'name':_('News'),
                            'search_terms':[],
@@ -166,7 +177,9 @@ class FieldMetadata(dict):
                            'link_column': 'tag',
                            'category_sort':'name',
                            'datatype':'text',
-                           'is_multiple':',',
+                           'is_multiple':{'cache_to_list': ',',
+                                          'ui_to_list': ',',
+                                          'list_to_ui': ', '},
                            'kind':'field',
                            'name':_('Tags'),
                            'search_terms':['tags', 'tag'],
@@ -176,7 +189,9 @@ class FieldMetadata(dict):
             ('identifiers',   {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':',',
+                           'is_multiple':{'cache_to_list': ',',
+                                          'ui_to_list': ',',
+                                          'list_to_ui': ', '},
                            'kind':'field',
                            'name':_('Identifiers'),
                            'search_terms':['identifiers', 'identifier', 'isbn'],
@@ -186,7 +201,7 @@ class FieldMetadata(dict):
             ('author_sort',{'table':None,
                             'column':None,
                             'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Author Sort'),
                            'search_terms':['author_sort'],
@@ -196,7 +211,9 @@ class FieldMetadata(dict):
             ('au_map',    {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':',',
+                           'is_multiple':{'cache_to_list': ',',
+                                          'ui_to_list': None,
+                                          'list_to_ui': None},
                            'kind':'field',
                            'name':None,
                            'search_terms':[],
@@ -206,7 +223,7 @@ class FieldMetadata(dict):
             ('comments',  {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Comments'),
                            'search_terms':['comments', 'comment'],
@@ -216,7 +233,7 @@ class FieldMetadata(dict):
             ('cover',     {'table':None,
                            'column':None,
                            'datatype':'int',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':None,
                            'search_terms':['cover'],
@@ -226,7 +243,7 @@ class FieldMetadata(dict):
             ('id',        {'table':None,
                            'column':None,
                            'datatype':'int',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':None,
                            'search_terms':[],
@@ -236,7 +253,7 @@ class FieldMetadata(dict):
             ('last_modified', {'table':None,
                            'column':None,
                            'datatype':'datetime',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Modified'),
                            'search_terms':['last_modified'],
@@ -246,7 +263,7 @@ class FieldMetadata(dict):
             ('ondevice',  {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('On Device'),
                            'search_terms':['ondevice'],
@@ -256,7 +273,7 @@ class FieldMetadata(dict):
             ('path',      {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Path'),
                            'search_terms':[],
@@ -266,7 +283,7 @@ class FieldMetadata(dict):
             ('pubdate',   {'table':None,
                            'column':None,
                            'datatype':'datetime',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Published'),
                            'search_terms':['pubdate'],
@@ -276,7 +293,7 @@ class FieldMetadata(dict):
             ('marked',    {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name': None,
                            'search_terms':['marked'],
@@ -286,7 +303,7 @@ class FieldMetadata(dict):
             ('series_index',{'table':None,
                              'column':None,
                              'datatype':'float',
-                             'is_multiple':None,
+                             'is_multiple':{},
                              'kind':'field',
                              'name':None,
                              'search_terms':['series_index'],
@@ -296,7 +313,7 @@ class FieldMetadata(dict):
             ('sort',      {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Title Sort'),
                            'search_terms':['title_sort'],
@@ -306,7 +323,7 @@ class FieldMetadata(dict):
             ('size',      {'table':None,
                            'column':None,
                            'datatype':'float',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Size'),
                            'search_terms':['size'],
@@ -316,7 +333,7 @@ class FieldMetadata(dict):
             ('timestamp', {'table':None,
                            'column':None,
                            'datatype':'datetime',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Date'),
                            'search_terms':['date'],
@@ -326,7 +343,7 @@ class FieldMetadata(dict):
             ('title',     {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':_('Title'),
                            'search_terms':['title'],
@@ -336,7 +353,7 @@ class FieldMetadata(dict):
             ('uuid',      {'table':None,
                            'column':None,
                            'datatype':'text',
-                           'is_multiple':None,
+                           'is_multiple':{},
                            'kind':'field',
                            'name':None,
                            'search_terms':[],
@@ -508,7 +525,7 @@ class FieldMetadata(dict):
         if datatype == 'series':
             key += '_index'
             self._tb_cats[key] = {'table':None,        'column':None,
-                                 'datatype':'float',   'is_multiple':None,
+                                 'datatype':'float',   'is_multiple':{},
                                  'kind':'field',       'name':'',
                                  'search_terms':[key], 'label':label+'_index',
                                  'colnum':None,        'display':{},
@@ -560,7 +577,7 @@ class FieldMetadata(dict):
         if icu_lower(label) != label:
             st.append(icu_lower(label))
         self._tb_cats[label] = {'table':None,          'column':None,
-                                'datatype':None,       'is_multiple':None,
+                                'datatype':None,       'is_multiple':{},
                                 'kind':'user',         'name':name,
                                 'search_terms':st,     'is_custom':False,
                                 'is_category':True,    'is_csp': False}
@@ -570,7 +587,7 @@ class FieldMetadata(dict):
         if label in self._tb_cats:
             raise ValueError('Duplicate user field [%s]'%(label))
         self._tb_cats[label] = {'table':None,        'column':None,
-                                'datatype':None,     'is_multiple':None,
+                                'datatype':None,     'is_multiple':{},
                                 'kind':'search',     'name':name,
                                 'search_terms':[],   'is_custom':False,
                                 'is_category':True,  'is_csp': False}
diff --git a/src/calibre/library/restore.py b/src/calibre/library/restore.py
index e03edd449a..20065309aa 100644
--- a/src/calibre/library/restore.py
+++ b/src/calibre/library/restore.py
@@ -171,7 +171,7 @@ class Restore(Thread):
                 for x in fields:
                     if x in cfm:
                         if x == 'is_multiple':
-                            args.append(cfm[x] is not None)
+                            args.append(bool(cfm[x]))
                         else:
                             args.append(cfm[x])
                 if len(args) == len(fields):
diff --git a/src/calibre/library/sqlite.py b/src/calibre/library/sqlite.py
index 511106fe7b..96874d2c27 100644
--- a/src/calibre/library/sqlite.py
+++ b/src/calibre/library/sqlite.py
@@ -121,9 +121,12 @@ class SortedConcatenate(object):
             return None
         return self.sep.join(map(self.ans.get, sorted(self.ans.keys())))
 
-class SafeSortedConcatenate(SortedConcatenate):
+class SortedConcatenateBar(SortedConcatenate):
     sep = '|'
 
+class SortedConcatenateAmper(SortedConcatenate):
+    sep = '&'
+
 class IdentifiersConcat(object):
     '''String concatenation aggregator for the identifiers map'''
     def __init__(self):
@@ -220,7 +223,8 @@ class DBThread(Thread):
         self.conn.execute('pragma cache_size=5000')
         encoding = self.conn.execute('pragma encoding').fetchone()[0]
         self.conn.create_aggregate('sortconcat', 2, SortedConcatenate)
-        self.conn.create_aggregate('sort_concat', 2, SafeSortedConcatenate)
+        self.conn.create_aggregate('sortconcat_bar', 2, SortedConcatenateBar)
+        self.conn.create_aggregate('sortconcat_amper', 2, SortedConcatenateAmper)
         self.conn.create_aggregate('identifiers_concat', 2, IdentifiersConcat)
         load_c_extensions(self.conn)
         self.conn.row_factory = sqlite.Row if self.row_factory else  lambda cursor, row : list(row)