# Locks

### Model lock

You can use lock using `with_lock` method on query collection:

```ruby
Clear::SQL.transaction do
    # SELECT * FROM users WHERE organization = 'Crystal Lang' FOR UPDATE
    User.where(organization: "Crystal Lang").with_lock.each do |user|
        # Do something with your users
    end
end
```

`with_lock` offers optional parameters (default: `"FOR UPDATE"`), to setup the lock options you want (ex: `with_lock("FOR UPDATE SKIP LOCKED")`)

See PostgreSQL [deep explanation about locking here](https://www.postgresql.org/docs/current/explicit-locking.html).

{% hint style="warning" %}
Lock work only inside transaction. Without transaction block, the call might fail.
{% endhint %}


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