In my rails app I have defined in the Kid model a calculation based on the fields from the Kids DB. the method is as follows:
def flip_date
self.dob.advance(months: 10)
end
I want to use this in my controller as I have a method where I am defining something as follows:
new_kids = Kid.where(discharge_date: nil).where('flip_date > ?', Date.current.advance(year: 1).beginning_of_year)
However I keep getting the following error:
SQLite3::SQLException: no such column: flip_date: SELECT "kids".* FROM "kids" WHERE "kids"."discharge_date" IS NULL AND (flip_date < '2017-01-01')
Any ideas on how can I make this work? All help is appreciated!
If you really want to use model methods take a look at http://apidock.com/rails/v4.0.2/ActiveRecord/QueryMethods/select
For your case:
new_kids = Kid.where(discharge_date: nil).select{|k| k.flip_date > Date.current.advance(year: 1).beginning_of_year}
But select method takes every object in memory before returning final result. Hence I will advise to use normal where clause and instead of flip_date take dob (which is a column in database) in consideration.
Like this
new_kids = Kid.where(discharge_date: nil).where('dob > ?', <date criteria>)
The select method (http://apidock.com/rails/v4.0.2/ActiveRecord/QueryMethods/select) works great if you are okay with the return being an Array.
I am still looking for a way to do this with an ActiveRecord_Relation return.
If others know how to do this, it would be much appreciated if you can share.
This example doesn't respond to your specific code, but to the extent it helps someone else with a similar question, here's a very simple example of how .select can be really handy:
#expired_memberships = User.select{|u| u.membership_expired_yesterday?}
In that example you've looped through all your Users and filtered them based on a custom method you defined on the User model (membership_expired_yesterday?). Now you can easily do stuff with that collection like this example in a mailer:
#expirations.each do |user|
MembershipExpirationMailer.with(user: user).first_reminder.deliver_now
end
Related
In my rails app I am fetching a batch of data from the DB with around a million records. I am simply calling the following query combined with some pagination logic, and right now it is working very well. The code is defined in my model, like so:
def find_records(current_page, max_records, start_value, end_value)
where(value_range: start_value..end_value)
.offset((current_page - 1) * max_records).limit(max_records)
end
However, in my previous attempt, I had the following code defined in my model:
def find_records(max_records, start_value, end_value)
where(value_range: start_value..end_value)
end
And I called .offset and .limit inside the controller like so:
def index
current_page = params[:page]
max_records = 3
start_value = 4
end_value = 8
Model.find_records(start_value, end_value).offset((current_page - 1) * max_records).limit(max_records)
end
When I did this, my memory completely gave up on the 3rd or 4th page and my app just crashed. I don't know why calling .limit and .offset in the model solved the issue.
So my question is, how does calling class methods in your model rather than the controller improve code execution performance? I mean this query is obviously data-related so it makes sense to call it inside the model anyways, but I would still like to know the wonders behind the magic.
Thank you!
how does calling class methods in your model rather than the controller improve code execution performance?
It should not. Both your queries return a ActiveRecord::Relation. Both offset and limit are used to build the query, so in both scenarios you should see the same query in your logs. Please check your development.log when in doubt.
Having the code query code in your model makes sense. The controller shouldn't know all those details.
About the pagination, there are a few solutions in the rails world - Kaminari, will_paginate
Is there any better way to find for a record based on custom model method?
def search
payments = all_payments.plans.order('payments.created_at DESC').select do |payment|
payment.plan == query
end
payments.paginate(pagination_params)
end
this takes and loads the entire table so the query is very slow.
payment.plan is an accessor from the model.
I can't afford to put a limit because it's unfair to the old records from the database.
Any idea? Thanks!
How about this:
payments = all_payments.plans.where(plan: query).order('payments.created_at DESC').paginate(pagination_params)
I am trying to search my database before I enter the record, by doing this:
Product.update_or_create_by_name_and_date_and_applicationURL_and_server_and_addi_servers(app_name, app_date,url_app,server_name,addi_servers)
the problem is that I get an undefined method exception!
Is there another way to search for the same record before entering one?
You should use two steps:
#Suggestion 1
obj = Product.find_or_create_by_...
#Suggestion 2
obj = Product.find_or_initialize_by_...
obj.update_attributes hash_here
Rereading, your question, I can't really understand what do you want to update if you try to find an object with known attributes. Anyway, you would just have to adapt my answer a little if some fields are for identifying and some for update.
I would define a function in your model: something like
Product.find_by_everything
where you write out all the parameters of the search, instead of using the the long naming method.
Then, if that returns nil, create the product. This doesn't seem to be a good use case of using the built in activerecord naming methods.
Seems like it should be able to look at a simple tutorial or find an aswer with a quick google, but I can't...
codes = PartnerCode.find_by_sql "SELECT * from partner_codes where product = 'SPANMEX' and isused = 'false' limit 1"
I want the column named code, I want just the value. Tried everything what that seems logical. Driving me nuts because everything I find shows an example without referencing the actual values returned
So what is the object returned? Array, hash, ActiveRecord? Thanks in advance.
For Rails 4+ (and a bit earlier I think), use pluck:
Partner.where(conditions).pluck :code
> ["code1", "code2", "code3"]
map is inefficient as it will select all columns first and also won't be able to optimise the query.
You need this one
Partner.where( conditions ).map(&:code)
is shorthand for
Partner.where( conditions ).map{|p| p.code}
PS
if you are often run into such case you will like this gem valium by ernie
it gives you pretty way to get values without instantiating activerecord object like
Partner.where( conditions ).value_of :code
UPDATED:
if you need access some attribute and after that update record
save instance first in some variable:
instance=Partner.where( conditions ).first
then you may access attributes like instance.code and update some attribute
instance.update_attribute || instance.update_attributes
check documentation at api.rubyonrails.org for details
I'm working on implementing a search form in a ruby on rails application. The general idea is to use form_tag to submit the search fields (via params) to a search function in the model of the class I'm trying to search. The search function will then iterate through each of the params and execute a scoping function if the name of the function appears in params.
The issue is that when I call the search on a collection like so:
#calendar.reservations.search({:search_email => "test"})
I don't know how to refer to the collection of #calendar.reservations from within the search function.
Additionally I'm confused as to why #calendar.reservations.search(...) works, but Reservations.all.search gives me an error saying you can't call an instance method on an array.
I've got the details of the search method over here: https://gist.github.com/783964
Any help would be greatly appreciated!
I don't know how to refer to the
collection of #calendar.reservations
from within the search function.
If you use self (or Reservation, it's the same object) inside the classmethod, you will access the records with the current scope, so in your case you will see only the reservations of a particular calendar.
[edit] I looked at you search function, and I think what you want is:
def self.search(search_fields)
search_fields.inject(self) do |scope, (key, value)|
scope.send(key, value)
end
end
Additionally I'm confused as to why
#calendar.reservations.search(...)
works, but Reservations.all.search
gives me an error saying you can't
call an instance method on an array.
#calendar.reservations does not return a standard array but a (lazy) AssociationCollection, where you can still apply scopes (and classmethods as your filter). On the other hand Reservation.all returns a plain array, so you cannot execute search there (or any scope, for that matter).
You don't really need a search method at all, as far as I can tell.
Simply use where:
#calendar.reservations.where(:search_email => 'test')
I would strongly encourage you to look at the MetaSearch GEM by Ernie Miller. It handles the kind of thing you're working on very elegantly and is quite easy to implement. I suspect that your view code would almost accomplish what the GEM needs already, and this would take care of all your model searching needs very nicely.
Take a look and see if it will solve your problem. Good luck!
Reservation.all.search doesn't work because it returns all the results as an array, while Reservation.where(..) returns an ActiveRecord object (AREL). Reservation.all actually fetches the results instead of just building the query further, which methods like where, limit etc do.