Rails - May 2007 - How do I stop a column being updated by model.save?

One of my models has a column that is updated very frequently from a
separate process, so it is important that when a record is saved in
rails, this column should be left alone. In the update method of the
controller I have:

@record = MyModel.find(params[:id])
@record.update_attributes(params[:my_model])

params[:my_model] doesn''t have a reference to the column I''m
talking
about, however, the UPDATE statement produced by update_attributes will
still assign a value to this column.

Even though its unlikely, if the separate process updates the record in
the time betweent the find, and the update, then the new value will be
lost. Is there a way to prevent this from happening?

p.s. attr_protected doesn''t help me

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On 5/21/07, David Fitzgibbon
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> One of my models has a column that is updated very frequently from a
> separate process, so it is important that when a record is saved in
> rails, this column should be left alone. In the update method of the
> controller I have:
>
> @record = MyModel.find(params[:id])
> @record.update_attributes(params[:my_model])
>
> params[:my_model] doesn''t have a reference to the column
I''m talking
> about, however, the UPDATE statement produced by update_attributes will
> still assign a value to this column.
>
> Even though its unlikely, if the separate process updates the record in
> the time betweent the find, and the update, then the new value will be
> lost. Is there a way to prevent this from happening?
>
One option, not very clean and elegant, and probably prone to
deadlocks if you update several rows during a transaction, is locking
the row & reading its'' current value from a before_save callback.

E.g.:

  def before_save
    unless self.new_record?
      current = self.class.find(self.id, :lock => true) # "select for
update", locking row
      write_attribute(:some_attribute, current.some_attribute)
    end
  end


Isak

> p.s. attr_protected doesn''t help me
>
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On May 21, 2007, at 10:19 AM, David Fitzgibbon wrote:
>
> One of my models has a column that is updated very frequently from a
> separate process, so it is important that when a record is saved in
> rails, this column should be left alone. In the update method of the
> controller I have:
>
> @record = MyModel.find(params[:id])
> @record.update_attributes(params[:my_model])
>
> params[:my_model] doesn''t have a reference to the column
I''m talking
> about, however, the UPDATE statement produced by update_attributes  
> will
> still assign a value to this column.
>
> Even though its unlikely, if the separate process updates the  
> record in
> the time betweent the find, and the update, then the new value will be
> lost. Is there a way to prevent this from happening?
>
> p.s. attr_protected doesn''t help me
The invocation is

   attr_readonly :foo

but according to

   http://dev.rubyonrails.org/ticket/6896

is scheduled for 1.2.4.

-- fxn


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

>   def before_save
>     unless self.new_record?
>       current = self.class.find(self.id, :lock => true) # "select
for
> update", locking row
>       write_attribute(:some_attribute, current.some_attribute)
>     end
>   end
> 
> 
> Isak
Its nasty, but it might work. Thanks!

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

hi david,

have you ever try this:
@record = MyModel.find(params[:id])
@record.update_attribute("your_column", params[:value])

for updating several column, you could use this instead:
@record.update_attribute("your_column1", params[:value1],
"your_column2",
params[:value2])

afaik, if you do somethink like this:
@record.update_attributes(params[:value])

then all your column will be updated using apt column-name with array of
:value, so that you previous value of column will be lost regardles.

regard,

~inung;


On 21/05/07, David Fitzgibbon
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
>
> >   def before_save
> >     unless self.new_record?
> >       current = self.class.find(self.id, :lock => true) #
"select for
> > update", locking row
> >       write_attribute(:some_attribute, current.some_attribute)
> >     end
> >   end
> >
> >
> > Isak
>
> Its nasty, but it might work. Thanks!
>
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>

-- 
in03ng a.k.a inung a.k.a nursamsi a.k.a nur syamsi
Y! in03ng

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

> @record.update_attribute("your_column", params[:value])
This has the same problem, both "update_attribute" and 
"update_attributes" call the "save" method, which in turn,
calls the
"update" method. This is whats setting the values of all the columns
in
the table.

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

sorry david, i''m wrong getting your first message. anyway, have u ever
try
using attr_accessible? n00b here, just trying to help...:D

regards,

~inung;


On 21/05/07, David Fitzgibbon
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
>
> > @record.update_attribute("your_column", params[:value])
>
> This has the same problem, both "update_attribute" and
> "update_attributes" call the "save" method, which in
turn, calls the
> "update" method. This is whats setting the values of all the
columns in
> the table.
>
> --
> Posted via http://www.ruby-forum.com/.
>
> >
>

-- 
in03ng a.k.a inung a.k.a nursamsi a.k.a nur syamsi
Y! in03ng

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

David Fitzgibbon wrote:
> One of my models has a column that is updated very frequently from a
> separate process, so it is important that when a record is saved in
> rails, this column should be left alone. In the update method of the
> controller I have:
>
> @record = MyModel.find(params[:id])
> @record.update_attributes(params[:my_model])
>
> params[:my_model] doesn''t have a reference to the column
I''m talking
> about, however, the UPDATE statement produced by update_attributes will
> still assign a value to this column.
>
> Even though its unlikely, if the separate process updates the record in
> the time betweent the find, and the update, then the new value will be
> lost. Is there a way to prevent this from happening?
>
> p.s. attr_protected doesn''t help me
>
>   
Check out optimistic locking.

-- 
Jack Christensen
jackc-/SOt/BrQZzMOf2zXYvRtkodd74u8MsAO@public.gmane.org


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---