diff -r aff75b69db92 -r 2c48c091b6a2 misc/migration/3.18.0_Any.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/misc/migration/3.18.0_Any.py	Mon Jan 13 13:47:47 2014 +0100
@@ -0,0 +1,129 @@
+driver = config.sources()['system']['db-driver']
+if not (driver == 'postgres' or driver.startswith('sqlserver')):
+    import sys
+    print >>sys.stderr, 'This migration is not supported for backends other than sqlserver or postgres (yet).'
+    sys.exit(1)
+
+sync_schema_props_perms('defaultval')
+
+def convert_defaultval(cwattr, default):
+    from decimal import Decimal
+    import yams
+    from cubicweb import Binary
+    if default is None:
+        return
+    atype = cwattr.to_entity[0].name
+    if atype == 'Boolean':
+        # boolean attributes with default=False were stored as ''
+        assert default in ('True', 'False', ''), repr(default)
+        default = default == 'True'
+    elif atype in ('Int', 'BigInt'):
+        default = int(default)
+    elif atype == 'Float':
+        default = float(default)
+    elif atype == 'Decimal':
+        default = Decimal(default)
+    elif atype in ('Date', 'Datetime', 'TZDatetime', 'Time'):
+        try:
+            # handle NOW and TODAY, keep them stored as strings
+            yams.KEYWORD_MAP[atype][default.upper()]
+            default = default.upper()
+        except KeyError:
+            # otherwise get an actual date or datetime
+            default = yams.DATE_FACTORY_MAP[atype](default)
+    else:
+        assert atype == 'String', atype
+        default = unicode(default)
+    return Binary.zpickle(default)
+
+dbh = repo.system_source.dbhelper
+
+
+sql('ALTER TABLE cw_cwattribute ADD new_defaultval %s' % dbh.TYPE_MAPPING['Bytes'])
+
+for cwattr in rql('CWAttribute X').entities():
+    olddefault = cwattr.defaultval
+    if olddefault is not None:
+        req = "UPDATE cw_cwattribute SET new_defaultval = %(val)s WHERE cw_eid = %(eid)s"
+        args = {'val': dbh.binary_value(convert_defaultval(cwattr, olddefault).getvalue()), 'eid': cwattr.eid}
+        sql(req, args, ask_confirm=False)
+
+sql('ALTER TABLE cw_cwattribute DROP COLUMN cw_defaultval')
+if driver == 'postgres':
+    sql('ALTER TABLE cw_cwattribute RENAME COLUMN new_defaultval TO cw_defaultval')
+else: # sqlserver
+    sql("sp_rename 'cw_cwattribute.new_defaultval', 'cw_defaultval', 'COLUMN'")
+
+
+# Set object type to "Bytes" for CWAttribute's "defaultval" attribute
+rql('SET X to_entity B WHERE X is CWAttribute, X from_entity Y, Y name "CWAttribute", '
+    'X relation_type Z, Z name "defaultval", B name "Bytes"')
+
+from yams import buildobjs as ybo
+schema.add_relation_def(ybo.RelationDefinition('CWAttribute', 'defaultval', 'Bytes'))
+schema.del_relation_def('CWAttribute', 'defaultval', 'String')
+
+commit()
+
+for rschema in schema.relations():
+    if rschema.symmetric:
+        subjects = set(repr(e.type) for e in rschema.subjects())
+        objects = set(repr(e.type) for e in rschema.objects())
+        assert subjects == objects
+        martians = set(str(eid) for eid, in sql('SELECT eid_to FROM %s_relation, entities WHERE eid_to = eid AND type NOT IN (%s)' %
+                                           (rschema.type, ','.join(subjects))))
+        martians |= set(str(eid) for eid, in sql('SELECT eid_from FROM %s_relation, entities WHERE eid_from = eid AND type NOT IN (%s)' %
+                                            (rschema.type, ','.join(subjects))))
+        if martians:
+            martians = ','.join(martians)
+            print 'deleting broken relations %s for eids %s' % (rschema.type, martians)
+            sql('DELETE FROM %s_relation WHERE eid_from IN (%s) OR eid_to IN (%s)' % (rschema.type, martians, martians))
+        with session.deny_all_hooks_but():
+            rql('SET X %(r)s Y WHERE Y %(r)s X, NOT X %(r)s Y' % {'r': rschema.type})
+    commit()
+
+
+# multi columns unique constraints regeneration
+from cubicweb.server import schemaserial
+
+# syncschema hooks would try to remove indices but
+# 1) we already do that below
+# 2) the hook expects the CWUniqueTogetherConstraint.name attribute that hasn't
+#    yet been added
+with session.allow_all_hooks_but('syncschema'):
+    rql('DELETE CWUniqueTogetherConstraint C')
+commit()
+
+add_attribute('CWUniqueTogetherConstraint', 'name')
+
+# low-level wipe code for postgres & sqlserver, plain sql ...
+if driver == 'postgres':
+    for indexname, in sql('select indexname from pg_indexes'):
+        if indexname.startswith('unique_'):
+            print 'dropping index', indexname
+            sql('DROP INDEX %s' % indexname)
+    commit()
+elif driver.startswith('sqlserver'):
+    for viewname, in sql('select name from sys.views'):
+        if viewname.startswith('utv_'):
+            print 'dropping view (index should be cascade-deleted)', viewname
+            sql('DROP VIEW %s' % viewname)
+    commit()
+
+# recreate the constraints, hook will lead to low-level recreation
+for eschema in sorted(schema.entities()):
+    if eschema._unique_together:
+        rql_args = schemaserial.uniquetogether2rqls(eschema)
+        for rql, args in rql_args:
+            args['x'] = eschema.eid
+            session.execute(rql, args)
+        commit()
+
+
+add_relation_definition('CWAttribute', 'add_permission', 'CWGroup')
+add_relation_definition('CWAttribute', 'add_permission', 'RQLExpression')
+
+# all attributes perms have to be refreshed ...
+for rschema in schema.relations():
+    if relation.final:
+        sync_schema_props_perms(rschema.type, syncprops=False)