diff --git a/rhodecode/model/db.py b/rhodecode/model/db.py
--- a/rhodecode/model/db.py
+++ b/rhodecode/model/db.py
@@ -35,7 +35,7 @@ import collections
 
 import pyotp
 from sqlalchemy import (
-    or_, and_, not_, func, cast, TypeDecorator, event, select,
+    or_, and_, not_, func, cast, TypeDecorator, event, select, delete,
     true, false, null, union_all,
     Index, Sequence, UniqueConstraint, ForeignKey, CheckConstraint, Column,
     Boolean, String, Unicode, UnicodeText, DateTime, Integer, LargeBinary,
@@ -274,6 +274,22 @@ class BaseModel(object):
         return stmt
 
     @classmethod
+    def delete(cls, custom_cls=None):
+        """
+        stmt = cls.delete().where(cls.user_id==1)
+        # optionally
+        stmt = cls.delete(User).where(cls.user_id==1)
+        result = cls.execute(stmt)
+        """
+
+        if custom_cls:
+            stmt = delete(custom_cls)
+        else:
+            stmt = delete(cls)
+        return stmt
+
+
+    @classmethod
     def execute(cls, stmt):
         return Session().execute(stmt)
 
@@ -1075,28 +1091,26 @@ class User(Base, BaseModel):
     @classmethod
     def get(cls, user_id, cache=False):
         if not user_id:
-            return
+            return None
 
         q = cls.select().where(cls.user_id == user_id)
         if cache:
-            q = q.options(
-                FromCache("sql_cache_short", f"get_users_{user_id}"))
+            q = q.options(FromCache("sql_cache_short", f"get_users_{user_id}"))
         return cls.execute(q).scalar_one_or_none()
 
     @classmethod
-    def get_by_username(cls, username, case_insensitive=False,
-                        cache=False):
+    def get_by_username(cls, username, case_insensitive=False, cache=False):
+        if not username:
+            return None
 
         if case_insensitive:
-            q = cls.select().where(
-                func.lower(cls.username) == func.lower(username))
+            q = cls.select().where(func.lower(cls.username) == func.lower(username))
         else:
             q = cls.select().where(cls.username == username)
 
         if cache:
             hash_key = _hash_key(username)
-            q = q.options(
-                FromCache("sql_cache_short", f"get_user_by_name_{hash_key}"))
+            q = q.options(FromCache("sql_cache_short", f"get_user_by_name_{hash_key}"))
 
         return cls.execute(q).scalar_one_or_none()
 
@@ -1125,6 +1139,8 @@ class User(Base, BaseModel):
 
     @classmethod
     def get_by_email(cls, email, case_insensitive=False, cache=False):
+        if not email:
+            return None
 
         if case_insensitive:
             q = cls.select().where(func.lower(cls.email) == func.lower(email))
@@ -1133,8 +1149,7 @@ class User(Base, BaseModel):
 
         if cache:
             email_key = _hash_key(email)
-            q = q.options(
-                FromCache("sql_cache_short", f"get_email_key_{email_key}"))
+            q = q.options(FromCache("sql_cache_short", f"get_email_key_{email_key}"))
 
         ret = cls.execute(q).scalar_one_or_none()
 
@@ -1147,8 +1162,8 @@ class User(Base, BaseModel):
                 q = q.where(UserEmailMap.email == email)
             q = q.options(joinedload(UserEmailMap.user))
             if cache:
-                q = q.options(
-                    FromCache("sql_cache_short", f"get_email_map_key_{email_key}"))
+                email_key = _hash_key(email)
+                q = q.options(FromCache("sql_cache_short", f"get_email_map_key_{email_key}"))
 
             result = cls.execute(q).scalar_one_or_none()
             ret = getattr(result, 'user', None)
@@ -1642,11 +1657,12 @@ class UserGroup(Base, BaseModel):
         return f"<{self.cls_name}('id:{self.users_group_id}:{self.users_group_name}')>"
 
     @classmethod
-    def get_by_group_name(cls, group_name, cache=False,
-                          case_insensitive=False):
+    def get_by_group_name(cls, group_name, cache=False, case_insensitive=False):
+        if not group_name:
+            return None
+
         if case_insensitive:
-            q = cls.query().filter(func.lower(cls.users_group_name) ==
-                                   func.lower(group_name))
+            q = cls.query().filter(func.lower(cls.users_group_name) == func.lower(group_name))
 
         else:
             q = cls.query().filter(cls.users_group_name == group_name)
@@ -2968,9 +2984,11 @@ class RepoGroup(Base, BaseModel):
 
     @classmethod
     def get_by_group_name(cls, group_name, cache=False, case_insensitive=False):
+        if not group_name:
+            return None
+
         if case_insensitive:
-            gr = cls.query().filter(func.lower(cls.group_name)
-                                    == func.lower(group_name))
+            gr = cls.query().filter(func.lower(cls.group_name) == func.lower(group_name))
         else:
             gr = cls.query().filter(cls.group_name == group_name)
         if cache: