Q:

Why Rails update_attributes is calling validation before saving

I am having a very strange problem in Rails. I am using update_attributes on a Parent Object to update all the children objects. The children objects have (custom) validation and indeed this works ok, meaning that if I give wrong values the validation trigger and I get an error back.
Now I am in a strange situation where one of the model is invalid in the database (let's not question why, let's just say I can go in the DB and run some SQL to make the model invalid). If I go in my app I can see the invalid values and this is fine. I fix the values and save again and I can see, stepping in the ruby code that the validation is called also BEFORE saving the new values, meaning that I will get an error and Rails will never execute the SQL to actually update the values to the correct ones.
I hope the above makes sense. Do you have any idea or do you think there is something I am overlooking?
SOLUTION:
What was happening was that a many-to-many relationship was validating the existing DB data before being replaced by the new data. Basically the structure was like this:
class User
    has_many :user_permissions
    has_many :permissions, :through => :model_permissions

class Permission
    has_many :user_permissions
    has_many :users, :through => :user_permissions

class UserPermission
    belongs_to :user
    belongs_to :permission
    validates_associated :user       # THIS was causing the problem
    validates_associated :permission # and THIS as well

I simply removed the validates_associated directive, since I am validating the linked records independently anyway.

A:

Well, Rails does run your validation prior to writing the data to the database (please refer to Active Record callback sequence), so having validation errors means that some piece of the model you are trying to save is not valid. It might an associated model containing errors with the validation turned on or just some missing part – in any case, just have a look at what are the errors you are getting.
In case (let's no question why either :) you want to skip validation - you are open to choose from #update_attribute (to update just one attribute), calling #save(false), using +udpate_all method of the model class or even go down to ActiveRecord::Base.connection.execute – none of these will ever bother you with validation errors :)

