Decrementing

In order to decrement values of an instance without running into concurrency issues, you may use decrement.

First of all you can define a field and the value you want to add to it.

User.findByPk(1).then(user => {
  return user.decrement('my-integer-field', {by: 2})
}).then(user => {
  // Postgres will return the updated user by default (unless disabled by setting { returning: false })
  // In other dialects, you'll want to call user.reload() to get the updated instance...
})

Second, you can define multiple fields and the value you want to add to them.

User.findByPk(1).then(user => {
  return user.decrement([ 'my-integer-field', 'my-very-other-field' ], {by: 2})
}).then(/* ... */)

Third, you can define an object containing fields and its decrement values.

User.findByPk(1).then(user => {
  return user.decrement({
    'my-integer-field':    2,
    'my-very-other-field': 3
  })
}).then(/* ... */)