I have query like this:
query = Link.select('url, max(created_at) as created_at, count(*) as url_count').group(:url).order('url_count desc, created_at asc')
Sample results of query.results.first:
2.2.0 :002 > query.first
=> #<Link id: nil, url: "http://1", created_at: "2015-03-10 16:43:54">
Why there is no url_count here, even though I know it is.
2.2.0 :003 > query.first.url_count
=> 17
The count is there all along but the model to_s method does not know about it.
The to_s method which is used when your console logs the result from query.first is defined somewhere in activerecord and it uses the attributes defined for the model in the database. Since your attribute is only defined for this particular instance of Link not for the model Link.
I found this quite interesting. Below is a description of how the message displayed in your console is constructed. It starts out in the gem active_attr with these 3 methods displayed below:
def inspect
attribute_descriptions = attributes.sort.map { |key, value| "#{key}: #{value.inspect}" }.join(", ")
separator = " " unless attribute_descriptions.empty?
"#<#{self.class.name}#{separator}#{attribute_descriptions}>"
end
# ...
def attributes
attributes_map { |name| send name }
end
# ...
def attributes_map
Hash[ self.class.attribute_names.map { |name| [name, yield(name)] } ]
end
the method attributes_names is defined in the gem activerecord
def attribute_names
#attribute_names ||= if !abstract_class? && table_exists?
column_names
else
[]
end
end
# ...
def column_names
#column_names ||= #connection.columns(#table_name).collect { |c| c.name }
end
And that is why your count does not show up.
If you really want it to show up in your console you could override the inspect method and add it there.
Related
I'm intrigued. How User.where(name: 'Foo').where(age: 20) works with only one database call?
Does the method where know if it is the last of the chain and change its behavior? And if so, how that can be done?
It returns self after each time it adds the query to its internal query builder.
where doesn't necessarily know where it's at; ActiveRecord waits for itself to be enumerated on before even querying the database. Example:
users = User.where(active: true)
users.loaded? # false
users.each { }
users.loaded? # true
each, map, first, last, etc. all will trigger the query to be loaded.
Here's an example of a super-naive query builder:
class FakeRecord
include Enumerable
def self.all_args
#all_args ||= []
end
def self.where(*args)
all_args << args
self
end
def self.each
puts "Executing sql #{all_args.join(", ")}"
yield [1, 2, 3]
end
end
FakeRecord.where(potato: true).where(dinosaur: false).each do |thing|
puts thing
end
I'm trying to add some additional functionality to where method in ActiveRecord. I reached half way by doing monkey patch but facing problem with chain queries.
Ex:
User.where(id: 10, name: 'Blob')
When I execute above code my new functionality is working as expected.
It triggers modified where method and gives query params as
query_params = { id: 10, name: 'Blob' }
User.where(id: 10).where(name: 'Blob')
In this case i'm getting only
query_params = { id: 10 }
I'm just printing the query params and delegating to super class:
def where(query, *values)
query.each do |key, value|
if value.is_a?(Array) and value.flatten != value
Rails.logger.debug "Where Clause Params"
Rails.logger.debug "#{query}"
Rails.logger.debug "#{caller.join("\n")}"
break
end
end
super
end
This is how I extend modified where file into ApplicationRecord
ApplicationRecord.extend CoreExtensions::ApplicationRecord::WhereLog
It would be great if anyone helps.
In a Rails 5.1 app, I have a query object (PORO) named CoolProducts.
class CoolProducts
def self.call(relation = Product.all)
...
# return an instance of Product::ActiveRecord_Relation
end
end
Now I need to limit the found Products based on the fact the name matches a string.
The following works
CoolProducts.call.where("name ILIKE ?", "%#{string}%")
However, I'd like to encapsulate the matching login within the CoolProducts class allowing to do something like
CoolProducts.call.including_in_name(string)
But I'm not sure where to start from.
Any ideas?
It will be difficult if you want any of your methods to be chainable or return ActiveRecord::Relation.
If you consider explicitly fetching the records when you're done chaining being ok, this should work:
class CoolProducts
def initialize(relation)
#relation = relation
end
def self.call(relation = Product.all)
new(relation).apply_scopes
end
attr_reader :relation
alias_method :fetch, :relation
def including_in_name(string)
tap { #relation = relation.where("name ILIKE ?", string) }
end
def apply_scopes
tap { #relation = relation.where(price: 123) }
end
end
Usage:
CoolProducts.call.including_in_name(string).fetch
I want to filter jobs on the parameter passed onto the model, currently search works flawlessly without query passed into the model, but when I type query it doesn't return anything. How can I perform this query with query and criteria.
results << model.with_query(query).where(criteria). any idea would be really appreciated.
module Refinery
class SearchEngine
# How many results should we show per page
RESULTS_LIMIT = 100
# Perform search over the specified models
def self.search(query, job_region, job_division, country, job_type, page = 1)
results = []
Refinery.searchable_models.each do |model|
criteria = {:job_region => job_region,
:job_division => job_division,
:country => country,
:job_type => job_type
}.select { |key, value| value.present? }
if query.present?
results << model.with_query(query).where(criteria)
else
results << model.limit(RESULTS_LIMIT).where(criteria)
end
end
results.flatten[0..(RESULTS_LIMIT - 1)]
end
end
end
The problem here is that the method .with_query(qry) returns an Array. You want to do chain-scoping, so you must use scopes that returns ActiveRecord::Relation objects.
model.with_query(query)
# returns an Array
model.with_query(query).where(criteria)
# calling .where on an Array object => NoMethodError
model.where(criteria)
# returns an ActiveRecord::Relation
model.where(criteria).with_query(query)
# calls the query on an AR::Relation object, which is doable
Short version: Change this:
results << model.with_query(query).where(criteria)
To this:
results << model.where(criteria).with_query(query)
What I'm trying to do: I have a model "Recipe" in which I defined a method "search" that takes an array of strings from checkboxes (I call them tags), and a single string. The idea is to search the db for recipes that has anything in it's 'name' or 'instructions' that contains the string, AND also has any of the tags matching it's 'tags' property.
Problem: The search method return all the recipes in my db, and doesn't seem to work at all at finding by the specific parameters.
The action method in the controller:
def index
#recipes = Recipe.search(params[:search], params[:tag])
if !#recipes
#recipes = Recipe.all
end
respond_to do |format|
format.html
format.json { render json: #recipe }
end
end
The search method in my model:
def self.search(search, tags)
conditions = ""
search.present? do
# Condition 1: recipe.name OR instruction same as search?
conditions = "name LIKE ? OR instructions LIKE ?, '%#{search[0].strip}%', '%#{search[0].strip}%'"
# Condition 2: if tags included, any matching?
if !tags.empty?
tags.each do |tag|
conditions += "'AND tags LIKE ?', '%#{tag}%'"
end
end
end
# Hämtar och returnerar alla recipes där codition 1 och/eller 2 stämmer.
Recipe.find(:all, :conditions => [conditions]) unless conditions.length < 1
end
Any ideas why it return all records?
if you are using rails 3, then it is easy to chain find conditions
def self.search(string, tags)
klass = scoped
if string.present?
klass = klass.where('name LIKE ? OR instructions LIKE ?', "%#{string}%", "%#{string}%")
end
if tags.present?
tags.each do |tag|
klass = klass.where('tags LIKE ?', "%#{tag}%")
end
end
klass
end
When you do
search.present? do
...
end
The contents of that block are ignored - it's perfectly legal to pass a block to a function that doesn't expect one, however the block won't get called unless the functions decides to. As a result, none of your condition building code is executed. You probably meant
if search.present?
...
end
As jvnill points out, it is in general much nicer (and safer) to manipulate scopes than to build up SQL fragments by hand