Rails validates uniqueness while updating object? - very strange -

so, have simple user model, , form updating password.

@user.update_attributes(:password=>params[:password]) 

but didn't work, , figured out:

user load (1.0ms)  select "users".* "users" "users"."auth_token" = 'z7ku4i0ixljirmpdf6sovq' limit 1   user load (0.0ms)  select "users".* "users" "users"."password_reset_token" = 'amojtn0ikpuojo2jmvodtq' limit 1    (0.0ms)  begin   user exists (1.0ms)  select 1 one "users" (lower("users"."email") = lower('somemail@mail.ru') , "users"."id" != 1) limit 1    (0.0ms)  rollback redirected http://localhost:3000/edit_user_by_reset?reset_token=amojtn0ikpuojo2jmvodtq 

by 3rd select can tell, here uniqueness validation failed! , reason rollback. doesn't make sense, of course there such row in db, update action. should do? don't want pass :validate=>false here.

if want update password field only, should not use mass_assignment method update_attributes, should use update_attribute(:password, params[:user][:password]).

there possible error params[:password] hash: if use form_for @user should have params[:user][:password] , in common params[:user] other fields.

you should check if given user valid (did save him db without validation).