I need to calculate values when saving a model in Rails. So I call calculate_averages as a callback for a Survey class:
before_save :calculate_averages
However, occasionally (and initially I have 10k records that need this operation) I need to manually update all the averages for every record. No problem, I have code like the following:
Survey.all.each do |survey|
survey.some_average = (survey.some_value + survey.some_other_value) / 2.to_f
#and some more averages...
survey.save!
end
Before even running this code, I'm worried the calculate_averages is going to get called and duplicate this and probably even cause some problems with the way I'm doing things. Ok, so then I think, well I'll just do nothing and let calculate_averages get called and do its thing. Problem there is, first, is there a way to force callbacks to get called even if you made no changes to the record?
Secondly, the way averages are calculated it's far more efficient to simply not let the callbacks get called at all and do the averages for everything all at once. Is this possible to not let callbacks get called?
I believe what you are asking for can be achieved with ActiveSupport::Callbacks. Have a look at set_callback and skip_callback.
In order to "force callbacks to get called even if you made no changes to the record", you need to register the callback to some event e.g. save, validate etc..
set_callback :save, :before, :my_before_save_callback
To skip the before_save callback, you would do:
Survey.skip_callback(:save, :before, :calculate_average).
Please reference the linked ActiveSupport::Callbacks on other supported options such as conditions and blocks to set_callback and skip_callback.
To disable en-mass callbacks use...
Survey.skip_callback(:save, :before, :calculate_averages)
Then to enable them...
Survey.set_callback(:save, :before, :calculate_average)
This skips/sets for all instances.
update_column is an ActiveRecord function which does not run any callbacks, and it also does not run validation.
Doesn't work for Rails 5
Survey.skip_callback(:save, :before, :calculate_average)
Works for Rails 5
Survey.skip_callback(:save, :before, :calculate_average, raise: false)
https://github.com/thoughtbot/factory_bot/issues/931
If you want to conditionally skip callbacks after checking for each survey you can write your custom method.
For ex.
Modified callback
before_save :calculate_averages, if: Proc.new{ |survey| !survey.skip_callback }
New instance method
def skip_callback(value = false)
#skip_callback = #skip_callback ? #skip_callback : value
end
Script to update surveys
Survey.all.each do |survey|
survey.some_average = (survey.some_value + survey.some_other_value) / 2.to_f
#and some more averages...
survey.skip_callback(true)
survey.save!
end
Its kinda hack but hope will work for you.
Rails 5.2.3 requiring an after party script to NOT trigger model events, update_column(column_name, value) did the trick:
task.update_column(task_status, ReferenceDatum::KEY_COMPLETED)
https://apidock.com/rails/ActiveRecord/Persistence/update_column
hopefully this is what you're looking for.
https://stackoverflow.com/a/6587546/2238259
For your second issue, I suspect it would be better to inspect when this calculation needs to happen, it would be best if it could be handled in batch at a specified time where network traffic is at its trough.
EDIT: Woops. I actually found 2 links but lost the first one, apparently. Hopefully you have it fixed.
For Rails 3 ActiveSupport::Callbacks gives you the necessary control. You can reset_callbacks en-masse, or use skip_callback to disable judiciously like this:
Vote.skip_callback(:save, :after, :add_points_to_user)
…after which you can operate on Vote instances with :add_points_to_user inhibited
Related
CODE
# Item Model
class Item < ActiveRecord::Base
attr_accessor :paid_amount
after_save :amount_processed?
def amount_processed?
if self.try(:paid_amount)
return true
else
return false
end
end
end
# Controller snippet
...
# params = {"paid_amount" => 10}
#item.assign_attributes(params)
if #item.valid?
#item.save
end
...
Currently the callback is not running, i.e., the code never checks amount_processed?. The reason this is happening is because paid_amount isn't a db attribute for Item. But that is by design. The question is ASSUMING this design were to stay, would there be a way for me to run a callback to check amount_processed? simply based on the fact that the attribute was passed? (i.e., if you run #item.paid_amount you'd get "10" after the #item.assign_attributes).
Note that the following callbacks will not work:
after_save or after_touch because as above, the paid_amount is never saved so the #item is never updated
after_find because this runs, by definition, before the attribute assignment. So with this validation, even though amount_processed? is checked, when it is checked, #item.paid_amount = nil
Would love to combine the two...
Since the question asks how to do this GIVEN current design, a perfectly acceptable answer is to say in the current design, it's not possible. The callback will only work if the attribute is actually updated. In that case, I already have 2 strategies to tackle this, the easiest of which being moving amount_processed? to the controller level so I can check the paid_amount after the assign_attributes. The other strategy is to have a Child of Item, but this is dependent on other info about the code that, for simplicity's sake, I have withheld.
Thanks!
Ook I think I have the answer here, thanks for the comments. Willem is right, in the current design, I can ensure amount_processed? is run by using a custom validation, changing the callback to:
validate :amount_processed?
However, doing so then makes the code a bit hacky, since I'm co-opting a validation to do the work of a callback. In other words, I would have to ensure amount_processed? always returned true (at end of the if statement; obviously other work would be done with paid_amount). There are some other considerations as well looking holistically at my code.
Given that, may change the design... but this was still a very helpful exercise
I'm having a weird issue for which I can't find a logical explanation.
I'm investigating a bug and put some logging in place (through Rollbar) so I can see the evolution some instances of one of my models.
Here is what I got:
class Connexion < ActiveRecord::Base
before_validation :save_info_in_rollbar
after_save :save_info_in_rollbar
def save_info_in_rollbar
Rollbar.log("debug", "Connexion save", :connexion_id => self.id, :connexion_details => self.attributes)
end
end
Now I am getting loads of data in rollbar (pretty much 2 rows for every time a connexion is created/updated). But the weird thing is the following: for some connexions (=> exactly the ones with faulty data which I am investigating), I am getting no data at all!
I don't get how it's possible for a connexion to be created and persisted to the DB, and not have any trace of the before_validation logging.
It looks like the callback is not called, but unless I'm mistaken, it's supposed to be the first one in the callback order => what could prevent it from being called?
EDIT >> Copy and paste from a reply, might be relevant:
There are 3 cases in which a connexion is created or updated, and thoses cases are :
.connexions.create()
connexion.attr = "value"; connexion.save!
connexion.update_attributes(attr: "value")
The only cases in which the callback won’t be run are:
Explicitly skipping validations (e.g. with save(validate: false))
Using an update method that skips Ruby-land (either partially or entirely, see each method’s linked docs) and just runs the SQL directly (e.g. update_columns, update_attribute, update_all).
But: I might be missing a case. Also, I’m assuming there isn’t a bug in ActiveRecord/ActiveModel causing this.
Sorry about the stupid question guys, the explanation was that we were having 2 apps working on the same database, and the modification was made by the other app (which of course was not sending the Rollbar updates).
Sometimes the toughest issues have the most simple answers haha
Firstly, you don't need self in instance methods, as the scope of the method is instance.
Secondly, you need to check, how are you saving the data to the database. You can skip callbacks in Rails: Rails 3 skip validations and callbacks
Thirdly, double check the data.
I have a function within a model that performs some actions after_save
Within that function I have the following code
progression = Progression.find_by_id(newprogression)
if progression.participation_id.nil?
progression.participation_id = participation.id
progression.save
else
What I am seeing is that progression is not being updated. Even though the following
if i check progression.participation_id before the save it has been updated
if in debugger I manually run progression.save I get true returned.
any thoughts?
I'm still pretty new to Rails, but every time I save something, I have to use a bang method. Have you tried progression.save!
Ok, I had the same problem and I managed to deal with it.
The problem was with association name. I had a model named User and a child model named Update, which had number of new updates of each user. So, in user.rb I had this line:
has_one :update
After I deleted this line, everything started working again. Looks like this is a rails reserved name and it should not be used when creating models. Perhaps you have some kind of the same problem here. It's a pity that Rails doesn't indicate this problem.
It might be a caching problem. From the rails guide on AR Relations - Sec 3.1, you might want to reload the cache by passing true. You are likely to encounter this, if you are checking it via participation, after establishing the link through progression.
Assuming Progression belongs_to Participation,
Can you try: progression.participation = participation and then progression.save
Also, try: participation.progressions << progression and participation.save ?
Try
progression = Progression.find_by_id(newprogression)
if progression.participation_id.nil?
progression.update_attributes(
:participation_id => participation.id
)
else
save and after_save run in the same transaction. maybe it's a problem. try to use after_commit callback
I have this loop
pages.each{|page| page.update_attribute(:sort_order, self.sort_order.to_i + 1)}
I used update_attribute to skip the before_update or before_save was not being called
before_save :set_data
before_update :set_data
but the set_data is being called again....any ideas on how to avoid this
I even tried the following
pages.each do |page|
page.sort_order = self.sort_order.to_i + 1
page.save(:validate => false)
end
I am trying to update and the later pages to a sort_order + 1 so I can have the pages in some order
Any ideas
The docs say that #update_attribute() and #save() invoke callbacks.
I had the same issue a few months ago and I don't think you can save a record without the callbacks being invoked.
Edit
I just saw #update_column() in the docs, which skips callbacks.
Seems that update_column might do the trick
What about this?
Page.where(:id => pages.collect(&:id)).update_all('sort_order=sort_order+1')
The advantage to this approach is you issue a single SQL query for an arbitrary number of rows. As a note, though, this will not alter the sort_order property of any models in memory.
This side-steps the entire callback chain. The documentation for update_attribute says that validation is skipped, but callbacks are invoked.
If I add an after_save callback to an ActiveRecord model, and on that callback I use update_attribute to change the object, the callback is called again, and so a 'stack overflow' occurs (hehe, couldn't resist).
Is it possible to avoid this behavior, maybe disabling the callback during it's execution? Or is there another approach?
Thanks!
One workaround is to set a variable in the class, and check its value in the after_save.
Check it first. (if var)
Assign it to a 'false' value before calling update_attribute.
call update_attribute.
Assign it to a 'true' value.
end
This way, it'll only attempt to save twice. This will likely hit your database twice, which may or may not be desirable.
I have a vague feeling that there's something built in, but this is a fairly foolproof way to prevent a specific point of recursion in just about any application.
I would also recommend looking at the code again, as it's likely that whatever you're doing in the after_save should be done in before_save. There are times that this isn't true, but they're fairly rare.
Could you use the before_save callback instead?
I didn't see this answer, so I thought I'd add it in case it helps anyone searching on this topic. (ScottD's without_callbacks suggestion is close.)
ActiveRecord provides update_without_callbacks for this situation, but it is a private method. Use send to get access to it anyway. Being inside a callback for the object you are saving is exactly the reason to use this.
Also there is another SO thread here that covers this pretty well:
How can I avoid running ActiveRecord callbacks?
Also you can look at the plugin Without_callbacks. It adds a method to AR that lets you skip certain call backs for a given block.
Example:
def your_after_save_func
YourModel.without_callbacks(:your_after_save_func) do
Your updates/changes
end
end
Check out how update_attribute is implemented. Use the send method instead:
send(name.to_s + '=', value)
If you use before_save, you can modify any additional parameters before the save is completed, meaning you won't have to explicitly call save.
This code doesn't even attempt to address threading or concurrency issues, much like Rails proper. If you need that feature, take heed!
Basically, the idea is to keep a count at what level of recursive calls of "save" you are, and only allow after_save when you are exiting the topmost level. You'll want to add in exception handling, too.
def before_save
#attempted_save_level ||= 0
#attempted_save_level += 1
end
def after_save
if (#attempted_save_level == 1)
#fill in logic here
save #fires before_save, incrementing save_level to 2, then after_save, which returns without taking action
#fill in logic here
end
#attempted_save_level -= 1 # reset the "prevent infinite recursion" flag
end
Thanks guys, the problem is that I update other objects too (siblings if you will)... forgot to mention that part...
So before_save is out of the question, because if the save fails all the modifications to the other objects would have to be reverted and that could get messy :)
The trick is just to use #update_column:
Validations are skipped.
Callbacks are skipped.
updated_at/updated_on are not updated.
Additionally, it simply issues a single quick update query to the db.
http://apidock.com/rails/ActiveRecord/Persistence/update_columns
I had this problem too. I need to save an attribute which depends upon the object id. I solved it by using conditional invocation for the callback ...
Class Foo << ActiveRecord::Base
after_save :init_bar_attr, :if => "bar_attr.nil?" # just make sure this is false after the callback runs
def init_bar_attr
self.bar_attr = "my id is: #{self.id}"
# careful now, let's save only if we're sure the triggering condition will fail
self.save if bar_attr
end
Sometimes this is because of not specifying attr_accessible in models. When update_attribute wants to edit the attributes, if finds out they are not accessible and create new objects instead.On saving the new objects, it will get into an unending loop.
I had a need to gsub the path names in a block of text when its record was copied to a different context:
attr_accessor :original_public_path
after_save :replace_public_path, :if => :original_public_path
private
def replace_public_path
self.overview = overview.gsub(original_public_path, public_path)
self.original_public_path = nil
save
end
The key to stop the recursion was to assign the value from the attribute and then set the attribute to nil so that the :if condition isn't met on the subsequent save.
You can use after_save in association with if as follows:
after_save :after_save_callback, if: Proc.new {
//your logic when to call the callback
}
or
after_save :after_save_callback, if: :call_if_condition
def call_if_condition
//condition for when to call the :after_save_callback method
end
call_if_condition is a method. Define the scenario when to call the after_save_callback in that method