permitted duplicate records

before:
```
SomeModel.ordered_find([1, 3, 2, 1])
=>  [#<SomeModel id: 1>, #<SomeModel id: 3>, #<SomeModel id: 2>]
```

after:
```
SomeModel.ordered_find([1, 3, 2, 1])
=>  [#<SomeModel id: 1>, #<SomeModel id: 3>, #<SomeModel id: 2>, #<SomeModel id: 1>]
```