I'd like to create a 'timeline' feature for an existing Card model. The Card already has_many Notes and has_many Attachments. I'd like to be able to:
access notes, attachments (and other models eventually) in a unified collection with a nice method like: card.timeline
still be able to access a card's notes and attachments like: card.notes
still be able to access a note's parent card like: note.card
be able to add items to the card's timeline, with an API like: card.timeline << note
I think I have my DB set up correctly, it's the association declaration I can't seem to get right. Here's my schema:
create_table "cards", :force => true do |t|
t.string "name"
end
create_table "timeline_items", :force => true do |t|
t.integer "card_id", :null => false # FK from cards table
t.integer "item_id", :null => false # FK from notes or attachments table
t.string "item_type", :null => false # either 'Note' or 'Attachment'
end
create_table "notes", :force => true do |t|
t.text "content"
end
create_table "attachments", :force => true do |t|
t.string "file_file_name"
end
Anyone know how I can achieve this using ActiveRecord? It's driving me fudging mental!
A starting point is:
class Card < ActiveRecord::Base
has_many :timeline_items
has_many :notes, :through => :timeline_items, :source => :item, :source_type => 'Note', :order => 'updated_at DESC'
has_many :attachments, :through => :timeline_items, :source => :item, :source_type => 'Attachment', :order => 'updated_at DESC'
end
class TimelineItem < ActiveRecord::Base
belongs_to :card
belongs_to :item, :polymorphic => true
end
class Note < ActiveRecord::Base
has_one :card, :through => :timeline_items
has_one :timeline_item, :as => :item
end
Thanks in advance
~Stu
Okay - after struggling on and off with this, I crack it within 10mins of posting to stackoverflow! Typical.
To save others from banging their heads against walls, here's what I had wrong:
Note should have been:
class Note < ActiveRecord::Base
has_one :card, :through => :timeline_item #not timeline_items
has_one :timeline_item, :as => :item
end
And that was it! I was trying to use the creation methods used in this article, but actually that's not required.
Here's the console output, showing that the sql statements are all using the timeline_items table:
1.9.2-p290 :009 > c = Card.find(547)
Card Load (0.3ms) SELECT `cards`.* FROM `cards` WHERE `cards`.`id` = 547 LIMIT 1
=> #<Card id: 547, name: "Duplicates appearing">
1.9.2-p290 :010 > c.notes.count
(0.3ms) SELECT COUNT(*) FROM `notes` INNER JOIN `timeline_items` ON `notes`.`id` = `timeline_items`.`item_id` WHERE `timeline_items`.`card_id` = 547 AND `timeline_items`.`item_type` = 'Note'
=> 4
1.9.2-p290 :011 > c.notes.last.card
Note Load (2.7ms) SELECT `notes`.* FROM `notes` INNER JOIN `timeline_items` ON `notes`.`id` = `timeline_items`.`item_id` WHERE `timeline_items`.`card_id` = 547 AND `timeline_items`.`item_type` = 'Note' ORDER BY updated_at ASC LIMIT 1
Card Load (3.2ms) SELECT `cards`.* FROM `cards` INNER JOIN `timeline_items` ON `cards`.`id` = `timeline_items`.`card_id` WHERE `timeline_items`.`item_id` = 620 AND `timeline_items`.`item_type` = 'Note' LIMIT 1
=> #<Card id: 547, name: "Duplicates appearing">
1.9.2-p290 :013 > c.notes << Note.new(:content => 'Holee Sheeet Dawg', :user_id => 1)
(0.2ms) BEGIN
SQL (0.6ms) INSERT INTO `notes` (`content`, `created_at`, `updated_at`, `user_id`) VALUES ('Holee Sheeet Dawg', '2012-09-07 11:38:55', '2012-09-07 11:38:55', 1)
(0.1ms) COMMIT
(0.1ms) BEGIN
SQL (0.3ms) INSERT INTO `timeline_items` (`card_id`, `created_at`, `item_id`, `item_type`, `updated_at`) VALUES (547, '2012-09-07 11:38:55', 625, 'Note', '2012-09-07 11:38:55')
(0.5ms) COMMIT
Note Load (1.8ms) SELECT `notes`.* FROM `notes` INNER JOIN `timeline_items` ON `notes`.`id` = `timeline_items`.`item_id` WHERE `timeline_items`.`card_id` = 547 AND `timeline_items`.`item_type` = 'Note' ORDER BY updated_at DESC
=> [#<Note id: 625, content: "Holee Sheeet Dawg", user_id: 1, created_at: "2012-09-07 11:38:55", updated_at: "2012-09-07 11:38:55">, .....]
1.9.2-p290 :014 > c.notes.count
(0.7ms) SELECT COUNT(*) FROM `notes` INNER JOIN `timeline_items` ON `notes`.`id` = `timeline_items`.`item_id` WHERE `timeline_items`.`card_id` = 547 AND `timeline_items`.`item_type` = 'Note'
=> 5
EDIT:
I just noticed that my requirement of having card.timeline wasn't met yet. Because the join is coming from multiple tables, I wasn't able to get AR to handle the join for me (ideally *card.timeline_items.join(:notes, :attachments)* would have done the trick).
To solve this, I added the following method to my card class:
def timeline
(self.notes + self.attachments).sort { |a,b| a.updated_at <=> b.updated_at }
end
Related
I've got an association that needs a few joins / custom queries. When trying to figure out how to implement this the repeated response is finder_sql. However in Rails 4.2 (and above):
ArgumentError: Unknown key: :finder_sql
My query to do the join looks like this:
'SELECT DISTINCT "tags".*' \
' FROM "tags"' \
' JOIN "articles_tags" ON "articles_tags"."tag_id" = "tags"."id"' \
' JOIN "articles" ON "article_tags"."article_id" = "articles"."id"' \
' WHERE articles"."user_id" = #{id}'
I understand that this can be achieved via:
has_many :tags, through: :articles
However if the cardinality of the join is large (i.e. a user has thousands of articles - but the system only has a few tags) it requires loading all the articles / tags:
SELECT * FROM articles WHERE user_id IN (1,2,...)
SELECT * FROM article_tags WHERE article_id IN (1,2,3...) -- a lot
SELECT * FROM tags WHERE id IN (1,2,3) -- a few
And of course also curious about the general case.
Note: also tried using the proc syntax but can't seem to figure that out:
has_many :tags, -> (user) {
select('DISTINCT "tags".*')
.joins('JOIN "articles_tags" ON "articles_tags"."tag_id" = "tags"."id"')
.joins('JOIN "articles" ON "article_tags"."article_id" = "articles"."id"')
.where('"articles"."user_id" = ?', user.id)
}, class_name: "Tag"
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR: column tags.user_id does not exist
SELECT DISTINCT "tags".* FROM "tags" JOIN "articles_tags" ON "articles_tags"."tag_id" = "tags"."id" JOIN "articles" ON "article_tags"."article_id" = "articles"."id" WHERE "tags"."user_id" = $1 AND ("articles"."user_id" = 1)
That is it looks like it is trying to inject the user_id onto tags automatically (and that column only exists on articles). Note: I'm preloading for multiple users so can't use user.tags without other fixes (the SQL pasted is what I'm seeing using exactly that!). Thoughts?
While this doesn't fix your problem directly - if you only need a subset of your data you can potentially preload it via a subselect:
users = User.select('"users".*"').select('COALESCE((SELECT ARRAY_AGG(DISTINCT "tags"."name") ... WHERE "articles"."user_id" = "users"."id"), '{}') AS tag_names')
users.each do |user|
puts user[:tag_names].join(' ')
end
The above is DB specific for Postgres (due to ARRAY_AGG) but an equivalent solution probably exists for other databases.
An alternative option might be to setup a view as a fake join table (again requires database support):
CREATE OR REPLACE VIEW tags_users AS (
SELECT
"users"."id" AS "user_id",
"tags"."id" AS "tag_id"
FROM "users"
JOIN "articles" ON "users"."id" = "articles"."user_id"
JOIN "articles_tags" ON "articles"."id" = "articles_tags"."article_id"
JOIN "tags" ON "articles_tags"."tag_id" = "tags"."id"
GROUP BY "user_id", "tag_id"
)
Then you can use has_and_belongs_to_many :tags (haven't tested - may want to set to readonly and can remove some of the joins and use if you have proper foreign key constraints setup).
So my guess is you are getting the error when you try to access #user.tags since you have that association inside the user.rb.
So I think what happens is when we try to access the #user.tags, we are trying to fetch the tags of the user and to that rails will search Tags whose user_id matches with currently supplied user's id. Since rails takes association name as modelname_id format by default, even if you don't have user_id it will try to search in that column and it will search (or add WHERE "tags"."user_id") no matter you want it to or not since ultimate goal is to find tags that are belongs to current user.
Of course my answer may not explain it 100%. Feel free to comment your thought or If you find anything wrong, let me know.
Short Answer
Ok, if I understand this correctly I think I have the solution, that just uses the core ActiveRecord utilities and does not use finder_sql.
Could potentially use:
user.tags.all.distinct
Or alternatively, in the user model change the has_many tags to
has_many :tags, -> {distinct}, through: :articles
You could create a helper method in user to retrieve this:
def distinct_tags
self.tags.all.distinct
end
The Proof
From your question I believe you have the following scenario:
A user can have many articles.
An article belongs to a single user.
Tags can belong to many articles.
Articles can have many tags.
You want to retrieve all the distinct tags a user has associated with the articles they have created.
With that in mind I created the following migrations:
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :name, limit: 255
t.timestamps null: false
end
end
end
class CreateArticles < ActiveRecord::Migration
def change
create_table :articles do |t|
t.string :name, limit: 255
t.references :user, index: true, null: false
t.timestamps null: false
end
add_foreign_key :articles, :users
end
end
class CreateTags < ActiveRecord::Migration
def change
create_table :tags do |t|
t.string :name, limit: 255
t.timestamps null: false
end
end
end
class CreateArticlesTagsJoinTable < ActiveRecord::Migration
def change
create_table :articles_tags do |t|
t.references :article, index: true, null:false
t.references :tag, index: true, null: false
end
add_index :articles_tags, [:tag_id, :article_id], unique: true
add_foreign_key :articles_tags, :articles
add_foreign_key :articles_tags, :tags
end
end
And the models:
class User < ActiveRecord::Base
has_many :articles
has_many :tags, through: :articles
def distinct_tags
self.tags.all.distinct
end
end
class Article < ActiveRecord::Base
belongs_to :user
has_and_belongs_to_many :tags
end
class Tag < ActiveRecord::Base
has_and_belongs_to_many :articles
end
Next seed the database with a lot of data:
10.times do |tagcount|
Tag.create(name: "tag #{tagcount+1}")
end
5.times do |usercount|
user = User.create(name: "user #{usercount+1}")
1000.times do |articlecount|
article = Article.new(user: user)
5.times do |tagcount|
article.tags << Tag.find(tagcount+usercount+1)
end
article.save
end
end
Finally in rails console:
user = User.find(3)
user.distinct_tags
results in following output:
Tag Load (0.4ms) SELECT DISTINCT `tags`.* FROM `tags` INNER JOIN `articles_tags` ON `tags`.`id` = `articles_tags`.`tag_id` INNER JOIN `articles` ON `articles_tags`.`article_id` = `articles`.`id` WHERE `articles`.`user_id` = 3
=> #<ActiveRecord::AssociationRelation [#<Tag id: 3, name: "tag 3", created_at: "2016-10-18 22:00:52", updated_at: "2016-10-18 22:00:52">, #<Tag id: 4, name: "tag 4", created_at: "2016-10-18 22:00:52", updated_at: "2016-10-18 22:00:52">, #<Tag id: 5, name: "tag 5", created_at: "2016-10-18 22:00:52", updated_at: "2016-10-18 22:00:52">, #<Tag id: 6, name: "tag 6", created_at: "2016-10-18 22:00:52", updated_at: "2016-10-18 22:00:52">, #<Tag id: 7, name: "tag 7", created_at: "2016-10-18 22:00:52", updated_at: "2016-10-18 22:00:52">]>
May be it is helpful to use eager_load to force ActiveRecord execute joins. It works as includes(:tags).references(:tags)
Here is a code snippet:
users.eager_load(:tags).map { |user| user.tag.inspect }
# equal to
users.includes(:tags).references(:tags).map { |user| user.tag.inspect }
Where users - is an ActiveRecord relation.
This code will hit a database at least twice:
Select only users ids (hopefully, not too many)
Select users with joins tags through article_tags avoiding
SELECT * FROM article_tags WHERE article_id IN (1,2,3...) -- a lot
You are on the right path with has_many :tags, through: :articles (or even better has_many :tags, -> {distinct}, through: :articles as Kevin suggests). But you should read a bit about includes vs preload vs eager_load. You are doing this:
User.preload(:tags).each {|u| ... }
But you should do this:
User.eager_load(:tags).each {|u| ... }
or this:
User.includes(:tags).references(:tags).each {|u| ... }
When I do that I get this query:
SELECT "users"."id" AS t0_r0,
"tags"."id" AS t1_r0,
"tags"."name" AS t1_r1
FROM "users"
LEFT OUTER JOIN "articles"
ON "articles"."user_id" = "users"."id"
LEFT OUTER JOIN "articles_tags"
ON "articles_tags"."article_id" = "articles"."id"
LEFT OUTER JOIN "tags"
ON "tags"."id" = "articles_tags"."tag_id"
But that is still going to send a lot of redundant stuff from the database to your app. This will be faster:
User.eager_load(:tags).distinct.each {|u| ... }
Giving:
SELECT DISTINCT "users"."id" AS t0_r0,
"tags"."id" AS t1_r0,
"tags"."name" AS t1_r1
FROM "users"
LEFT OUTER JOIN "articles"
ON "articles"."user_id" = "users"."id"
LEFT OUTER JOIN "articles_tags"
ON "articles_tags"."article_id" = "articles"."id"
LEFT OUTER JOIN "tags"
ON "tags"."id" = "articles_tags"."tag_id"
Doing just User.first.tags.map &:name gets me joins too:
SELECT DISTINCT "tags".*
FROM "tags"
INNER JOIN "articles_tags"
ON "tags"."id" = "articles_tags"."tag_id"
INNER JOIN "articles"
ON "articles_tags"."article_id" = "articles"."id"
WHERE "articles"."user_id" = ?
For more details, please see this github repo with an rspec test to see what SQL Rails is using.
There are three possible solutions:
1) Continue to use has_many associations
Fake user_id column by adding it to the selected columns.
class User < ActiveRecord::Base
has_many :tags, -> (user) {
select(%Q{DISTINCT "tags".*, #{user_id} AS user_id })
.joins('JOIN "articles_tags" ON "articles_tags"."tag_id" = "tags"."id"')
.joins('JOIN "articles" ON "article_tags"."article_id" = "articles"."id"')
.where('"articles"."user_id" = ?', user.id)
}, class_name: "Tag"
end
2) Add an instance method on the User class
If you are using tags for queries only and you haven't used it in joins you can use this approach:
class User
def tags
select(%Q{DISTINCT "tags".*})
.joins('JOIN "articles_tags" ON "articles_tags"."tag_id" = "tags"."id"')
.joins('JOIN "articles" ON "article_tags"."article_id" = "articles"."id"')
.where('"articles"."user_id" = ?', id)
end
end
Now user.tags behaves like an association for all practical purposes.
3) OTOH, using EXISTS might be performant than using distinct
class User < ActiveRecord::Base
def tags
exists_sql = %Q{
SELECT 1
FROM articles,
articles_tags
WHERE "articles"."user_id" = #{id} AND
"articles_tags"."article_id" = "article"."id" AND
"articles_tags"."tag_id" = "tags.id"
}
Tag.where(%Q{ EXISTS ( #{exists_sql} ) })
end
end
I've been working on implementing a new model that belongs to one of our web apps existing models. Eventually, I want to build out a nested form. I understand that the form, and strong params can have it's own suite of issues, but I am currently struggling to get the models to behave as I would expect in the rails console.
Rails 4.2.7, Postgres DB
UPDATE - 10/3/16 - Still trying to find the right solution, but have made some changes
Our work is with Schools and Districts, and this particular case deals with surveys and how a survey is assigned to a school and district. Until now, a survey has been assigned to a district with a SurveyAssignment model, and some down the line logic assumed that all schools in a district were also "assigned" to the survey. Now, we want to be able to add more granularity to the SurveyAssignment and allow some specificity at the school level.
So I created a SchoolSurveyAssignment model and started to get the bits in place.
Here is the relevant model info:
class District < ActiveRecord::Base
...
has_many :schools, dependent: :destroy
has_many :survey_assignments, dependent: :destroy
...
end
class School
...
belongs_to :district
has_many :school_survey_assignments
has_many :survey_assignments, :through => :school_survey_assignments
...
end
class SurveyAssignment
belongs_to :district
belongs_to :survey
has_one :survey_version, through: :survey
has_many :school_survey_assignments, inverse_of: survey_assignment
has_many :schools, :through => :school_survey_assignments
accepts_nested_attributes_for :school_survey_assignments
attr_accessor :survey_group, :survey_version_type, :survey_version_id, :school_survey_assignments_attributes
validates :survey_id, presence: true
end
class SchoolSurveyAssignment
belongs_to :survey_assignment, inverse_of: :school_survey_assignments
belongs_to :school
attr_accessor :school_id, :survey_assignment_id, :grades_affected, :ulc_affected
validates_presence_of :survey_assignment
validates :school_id, presence: true, uniqueness: {scope: :survey_assignment_id}
end
Relevant Controller code:
class SurveyAssignmentsController < ApplicationController
before_action :set_district
before_action :set_survey_assignment, only: [:show, :edit, :update, :destroy]
respond_to :html, :json, :js
def new
#new_survey_assignment = SurveyAssignment.new()
#district.schools.each do |school|
#new_survey_assignment.school_survey_assignments.build(school_id: school.id)
end
end
def create
#survey_assignment = SurveyAssignment.new(survey_assignment_params)
if #survey_assignment.save
flash[:notice] = "Survey successfully assigned to #{#district.name}"
else
flash[:alert] = "There was a problem assigning this survey to #{#district.name}"
end
redirect_to district_survey_assignments_path(#district)
end
def survey_assignment_params
params.require(:survey_assignment).permit(:survey_id, :status, :survey_version_id, school_survey_assignments_attributes: [:id, :survey_assignment_id, :school_id, grades_affected: [], ulc_affected: []]).tap do |p|
p[:district_id] = #district.id
p[:school_year] = session[:selected_year]
end
end
def set_district
#district = District.find(params[:district_id])
end
Here is the relevant schema info:
create_table "school_survey_assignments", force: :cascade do |t|
t.integer "survey_assignment_id"
t.integer "school_id"
t.integer "grades_affected", default: [], array: true
t.string "ulc_affected", default: [], array: true
end
add_index "school_survey_assignments", ["school_id"], name: "index_school_survey_assignments_on_school_id", using: :btree
add_index "school_survey_assignments", ["survey_assignment_id"], name: "index_school_survey_assignments_on_survey_assignment_id", using: :btree
create_table "survey_assignments", force: :cascade do |t|
t.integer "district_id"
t.integer "survey_id"
t.integer "status"
t.datetime "created_at"
t.datetime "updated_at"
t.integer "school_year"
t.integer "last_response_status_id"
end
add_index "survey_assignments", ["district_id"], name: "index_survey_assignments_on_district_id", using: :btree
Once these were in place, I stepped into my rails console and attempted the following:
2.3.1 :002 > sa1 = SurveyAssignment.create(district_id: 3, survey_id: 508, school_year: 2017)
(0.2ms) BEGIN
SQL (0.7ms) INSERT INTO "survey_assignments" ("district_id", "survey_id", "school_year", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id" [["district_id", 3], ["survey_id", 508], ["school_year", 2017], ["created_at", "2016-09-30 21:30:20.205144"], ["updated_at", "2016-09-30 21:30:20.205144"]]
(7.2ms) COMMIT
=> #<SurveyAssignment id: 369, district_id: 3, survey_id: 508, status: nil, created_at: "2016-09-30 21:30:20", updated_at: "2016-09-30 21:30:20", school_year: 2017, last_response_status_id: nil>
2.3.1 :003 > sa2 = SurveyAssignment.create(district_id: 3, survey_id: 508, school_year: 2017)
(0.3ms) BEGIN
SQL (0.4ms) INSERT INTO "survey_assignments" ("district_id", "survey_id", "school_year", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5) RETURNING "id" [["district_id", 3], ["survey_id", 508], ["school_year", 2017], ["created_at", "2016-09-30 21:30:30.701197"], ["updated_at", "2016-09-30 21:30:30.701197"]]
(0.5ms) COMMIT
=> #<SurveyAssignment id: 370, district_id: 3, survey_id: 508, status: nil, created_at: "2016-09-30 21:30:30", updated_at: "2016-09-30 21:30:30", school_year: 2017, last_response_status_id: nil>
So now, I've successfully created two Survey Assignments. I'm now going to create two School Survey Assignments off of sa1:
2.3.1 :004 > [{school_id: 5}, {school_id: 6}].each do |ssa|
2.3.1 :005 > sa1.school_survey_assignments.create(ssa)
2.3.1 :006?> end
(0.2ms) BEGIN
SchoolSurveyAssignment Exists (2.4ms) SELECT 1 AS one FROM "school_survey_assignments" WHERE ("school_survey_assignments"."school_id" = 5 AND "school_survey_assignments"."survey_assignment_id" = 369) LIMIT 1
SQL (0.4ms) INSERT INTO "school_survey_assignments" ("survey_assignment_id") VALUES ($1) RETURNING "id" [["survey_assignment_id", 369]]
(6.4ms) COMMIT
(0.6ms) BEGIN
SchoolSurveyAssignment Exists (0.4ms) SELECT 1 AS one FROM "school_survey_assignments" WHERE ("school_survey_assignments"."school_id" = 6 AND "school_survey_assignments"."survey_assignment_id" = 369) LIMIT 1
SQL (0.3ms) INSERT INTO "school_survey_assignments" ("survey_assignment_id") VALUES ($1) RETURNING "id" [["survey_assignment_id", 369]]
(0.4ms) COMMIT
=> [{:school_id=>5}, {:school_id=>6}]
2.3.1 :007 > sa1.save
(0.3ms) BEGIN
(0.4ms) COMMIT
=> true
Now, it looks like I've successfully created two SchoolSurveyAssignments with survey_assignment_id = 369 and school_ids = 5 and 6
2.3.1 :008 > sa1.school_survey_assignments
SchoolSurveyAssignment Load (0.3ms) SELECT "school_survey_assignments".* FROM "school_survey_assignments" WHERE "school_survey_assignments"."survey_assignment_id" = $1 [["survey_assignment_id", 369]]
=> #<ActiveRecord::Associations::CollectionProxy [#<SchoolSurveyAssignment id: 5, survey_assignment_id: 369, school_id: nil, grades_affected: [], ulc_affected: []>, #<SchoolSurveyAssignment id: 6, survey_assignment_id: 369, school_id: nil, grades_affected: [], ulc_affected: []>]>
As you can see from the ActivRecord::Associations::CollectionProxy, both of the SchoolSurveyAssignments were created, with survey_assignment_id: 369, but with a nil school_id. This is troubling as it seems to be
Ignoring the parameters being passed into the create function, and
ignoring the validation of school_id
Another item that I don't understand is the following:
2.3.1 :009 > SchoolSurveyAssignment.find(5).survey_assignment_id
SchoolSurveyAssignment Load (0.6ms) SELECT "school_survey_assignments".* FROM "school_survey_assignments" WHERE "school_survey_assignments"."id" = $1 LIMIT 1 [["id", 5]]
=> nil
2.3.1 :011 > SchoolSurveyAssignment.find(5).survey_assignment.id
SchoolSurveyAssignment Load (0.3ms) SELECT "school_survey_assignments".* FROM "school_survey_assignments" WHERE "school_survey_assignments"."id" = $1 LIMIT 1 [["id", 5]]
SurveyAssignment Load (0.4ms) SELECT "survey_assignments".* FROM "survey_assignments" WHERE "survey_assignments"."id" = $1 LIMIT 1 [["id", 369]]
=> 369
Calling .survey_assignment_id should return the attribute on the SchoolSurveyAssignment and give 369. .survey_assignment.id is simply just grabbing the parent object's ID. I would expect both to return the same value, but one returns nil.
The end use case is making a SurveyAssignment form that lets the user set the attributes for a new SurveyAssignment and also set the attributes for X number of SchoolSurveyAssignments (based on # of schools in a district; varies from 2 to 15). Once I get a better grasp on how these models are interacting, I feel confident in executing this goal, but the behavior I'm seeing doesn't make sense to me, and I was hoping to find some clarity on implementing these related models. I feel like I'm bouncing around the answer, but am missing a key detail.
Thanks,
Alex
Try removing your attr_accessor lines of code. attr_accessor shouldn't be used for attributes that are persisted in the database and it's probably messing up the methods that ActiveRecord already provides by default, causing those attributes to not be saved properly
class SurveyAssignment
belongs_to :district
belongs_to :survey
has_one :survey_version, through: :survey
has_many :school_survey_assignments, inverse_of: survey_assignment
has_many :schools, :through => :school_survey_assignments
accepts_nested_attributes_for :school_survey_assignments
validates :survey_id, presence: true
end
class SchoolSurveyAssignment
belongs_to :survey_assignment, inverse_of: :school_survey_assignments
belongs_to :school
validates_presence_of :survey_assignment
validates :school_id, presence: true, uniqueness: {scope: :survey_assignment_id}
end
For the first question, School and SurveyAssignment don't know each other, school_id becomes nil. In your app, these models have m-to-n association indirectly, so how about using has_many through association between models?
In School model, add below:
has_many :survey_assignments, :through => :school_survey_assignments
In SurveyAssignments model, add below:
has_many :schools, :through => :school_survey_assignments
For the last question, both codes seem to be same..
I'm looking for help debugging an issue with a Rails has_many :through association. I have 3 models, Package, Venue, and my join table, Packagevenue
package.rb
class Package < ActiveRecord::Base
has_many :packagevenues
has_many :venues, through: :packagevenues
end
venue.rb
class Venue < ActiveRecord::Base
has_many :packagevenues
has_many :packages, through: :packagevenues
end
packagevenue.rb
class Packagevenue < ActiveRecord::Base
belongs_to :venues
belongs_to :packages
end
schema for packagevenues table
create_table "packagevenues", force: :cascade do |t|
t.integer "package_id"
t.integer "venue_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
Test Case:
Packagevenue.first
Packagevenue Load (0.3ms) SELECT "packagevenues".* FROM "packagevenues" ORDER BY "packagevenues"."id" ASC LIMIT 1
=> #<Packagevenue:0x007fac12209750> {
:id => 1,
:package_id => 2,
:venue_id => 1,
.....
}
[11] webapp » p=Package.find(2)
Package Load (0.2ms) SELECT "packages".* FROM "packages" WHERE "packages"."id" = $1 LIMIT 1 [["id", 2]]
=> #<Package:0x007fac14eae738> {
:id => 2,
.....
}
[12] webapp » v=Venue.find(1)
Venue Load (0.2ms) SELECT "venues".* FROM "venues" WHERE "venues"."id" = $1 LIMIT 1 [["id", 1]]
=> #<Venue:0x007fac1222e488> {
:id => 1,
.....
}
[13] webapp » v.packages
NameError: uninitialized constant Venue::Packages
.....
[14] webapp » p.venues
NameError: uninitialized constant Package::Venues
.....
I thought I did all of the setup correctly, can somebody please let me know why the Uninitialized Constant error keeps popping up?
The likely cause is due to the plurality of the belongs_to symbols in your Packagevenue model. You want those to be singular like so:
class Packagevenue < ActiveRecord::Base
belongs_to :venue
belongs_to :package
end
I'm new to Rails and I'm having an issue with models using "different" primary/foreign key naming conventions than supported by Rails. (OK, I think this MIGHT be the problem)
So these are my 2 models:
class Project < ActiveRecord::Base
self.primary_key = "PROJECT_ID"
has_many :employees, :foreign_key => "PROJECT_ID"
end
class Employee < ActiveRecord::Base
self.primary_key = "EMPLOYEE_ID"
belongs_to :project, :primary_key => "PROJECT_ID"
end
And this is what's driving me nuts:
> p = Project.find(2)
Project Load (0.2ms) SELECT "projects".* FROM "projects" WHERE "projects"."PROJECT_ID" = ? LIMIT 1 [[nil, 2]]
=> #<Project project_id: 2, name: "Project 2", created_at: "2013-08-18 21:26:33.538007", updated_at: "2013-08-18 21:26:33.538007">
> p.employees.inspect
Employee Load (0.2ms) SELECT "employees".* FROM "employees" WHERE "employees"."PROJECT_ID" = ? **[[nil, nil]]**
=> "#<ActiveRecord::Associations::CollectionProxy []>"
For some reason I don't receive the employees with project_id = 2. It seems that the ? gets substituted with nil.
It works the other way round, check this out
> e = Employee.find_by_project_id(2)
Employee Load (0.2ms) SELECT "employees".* FROM "employees" WHERE "employees"."project_id" = 2 LIMIT 1
=> #<Employee employee_id: 2, first_name: "Will", last_name: "Smith", project_id: 2, created_at: "2013-08-18 21:21:47.884919", updated_at: "2013-08-18 21:22:48.263970">
> e.project.inspect
Project Load (0.2ms) SELECT "projects".* FROM "projects" WHERE "projects"."PROJECT_ID" = ? ORDER BY "projects"."PROJECT_ID" ASC LIMIT 1 [[nil, 2]]
=> "#<Project project_id: 2, name: \"Project 2\", created_at: \"2013-08-18 21:26:33.538007\", updated_at: \"2013-08-18 21:26:33.538007\">"
What am I missing?
Try this:
class Project < ActiveRecord::Base
self.primary_key = "PROJECT_ID"
has_many :employees
end
class Employee < ActiveRecord::Base
attr_accessible :project
self.primary_key = "EMPLOYEE_ID"
belongs_to :project
end
Try to avoid upper case column names at all cost.
for the record here my schema.rb
create_table "employees", :primary_key => "EMPLOYEE_ID", :force => true do |t|
t.integer "project_id"
end
create_table "projects", :primary_key => "PROJECT_ID", :force => true do |t|
end
Try the following:
class Project < ActiveRecord::Base
self.primary_key = "PROJECT_ID"
has_many :employees, :foreign_key => "PROJECT_ID", :primary_key => "PROJECT_ID"
end
class Employee < ActiveRecord::Base
self.primary_key = "EMPLOYEE_ID"
belongs_to :project, :primary_key => "PROJECT_ID", :foreign_key => "PROJECT_ID"
end
If you use uppercased field names (i am not sure based on your question) then make sure you always use uppercased names (e.g. find_by_PROJECT_ID). Rails and ActiveRecord are case sensitive.
I'm experiencing some pretty slow load times with one of the pages of my Rails app. I have made some headway in my attempts to improve performance, but not as much as I had hoped. I'm wondering if I'm doing something silly to cause myself this grief or if anyone could offer me advice to better optimize my models/migrations/queries/views. I'm running Rails 3.1 and using PostgreSQL. This is what I've tried so far:
added includes(:items => :category) to the controller's query, as an attempt to fetch all the ItemCategories in advance, rather than running additional queries when outfits_helper requires them.
rendering partials as collections, rather than iterating through arrays/relations manually
added indexes to tables that are being accessed by the problematic controller action / view
outfits table: indexes for user_id and category_id
items table: indexes for user_id and category_id
outfit_items table: indexes for item_id, outfit_id, and [outfit_id, item_id]
Below are the relevant parts of my code:
Controller
# outfits_controller.rb
NUM_OUTFITS_PER_PAGE = 8
def other_users_outfits
# using Kaminari for pagination
#outfits = Outfit.does_not_belong_to_user(current_user).in_category_with_id(category_id).includes(:items => :category).page(params[:page]).per(NUM_OUTFITS_PER_PAGE)
end
Models
# outfit.rb
has_many :items, :through => :outfit_items
belongs_to :category, :class_name => 'OutfitCategory'
scope :does_not_belong_to_user, proc {|user| where('user_id != ?', user.id) }
scope :in_category_with_id, proc {|cat_id|
if cat_id.blank?
scoped
else
where(:category_id => cat_id)
end
}
.
# outfit_item.rb
belongs_to :item
belongs_to :outfit
.
# item.rb
has_many :outfit_items
has_many :outfits, :through => :outfit_items
belongs_to :category, :class_name => 'ItemCategory'
.
# item_category.rb
has_many :items, :foreign_key => 'category_id'
.
outfit_category.rb
has_many :outfits, :foreign_key => 'outfit_id'
Migrations
# create_outfits.rb
def self.up
create_table :outfits do |t|
t.column :category_id, :integer
t.column :user_id, :integer
t.timestamps
end
add_index :outfits, :category_id
add_index :outfits, :user_id
end
.
# create_outfit_items.rb
def self.up
create_table :outfit_items, :id => false do |t|
t.column :item_id, :integer
t.column :outfit_id, :integer
t.timestamps
end
add_index :outfit_items, :item_id
add_index :outfit_items, :outfit_id
add_index :outfit_items, [:outfit_id, :item_id]
end
.
# create_items.rb
def self.up
create_table :items do |t|
t.column :category_id, :integer
t.column :user_id, :integer
t.timestamps
end
add_index :items, :category_id
add_index :items, :user_id
end
.
# create_item_categories.rb
def self.up
create_table :item_categories do |t|
t.column :name, :string
t.column :category_type, :string
t.timestamps
end
end
.
# create_outfit_categories.rb
def self.up
create_table :outfit_categories do |t|
t.column :name, :string, :limit => 100, :null => false
t.timestamps
end
end
Views
# other_users_outfits.html.haml
= render :partial => 'other_users_outfit', :collection => outfits, :as => :outfit
.
# _other_users_outfit.html.haml
.outfit
.primary-items
= render :partial => 'other_users_outfit_primary_item', :collection => primary_outfit_items_top_to_bottom(outfit), :as => :item
.secondary-items
= render :partial => 'other_users_outfit_secondary_item', :collection => secondary_outfit_items(outfit), :as => :item
.
# _other_users_outfit_primary_item.html.haml
= image_tag item.image_url(:outfit_item), :class => 'primary-outfit-item'
.
# _other_users_outfit_secondary_item.html.haml
= image_tag item.image_url(:baby_thumb), :class => 'secondary-outfit-item'
Helper
# outfits_helper.rb
def primary_outfit_items_top_to_bottom(outfit)
primary_items = []
primary_items.push(outfit_item_in_category(outfit, 'Tops'))
primary_items.push(outfit_item_in_category(outfit, 'Full-lengths'))
primary_items.push(outfit_item_in_category(outfit, 'Bottoms'))
primary_items.push(outfit_item_in_category(outfit, 'Footwear'))
primary_items.compact
end
def secondary_outfit_items(outfit)
outfit.items.select{|item| item.category.category_type == 'secondary' }
end
def outfit_item_in_category(outfit, cat_name)
outfit.items.select{|item| item.category.name == cat_name }.first
end
Console Output
User Load (1.0ms) SELECT DISTINCT users.id, users.* FROM "users" WHERE "users"."id" = 3 LIMIT 1
(0.5ms) SELECT COUNT(count_column) FROM (SELECT 1 AS count_column FROM "outfits" WHERE (user_id != 3) LIMIT 8 OFFSET 0) subquery_for_count
Outfit Load (0.7ms) SELECT DISTINCT outfits.id, outfits.* FROM "outfits" WHERE (user_id != 3) ORDER BY outfits.created_at DESC LIMIT 8 OFFSET 0
OutfitItem Load (0.6ms) SELECT "outfit_items".* FROM "outfit_items" WHERE "outfit_items"."outfit_id" IN (28, 27, 26, 25, 24, 23, 22, 21)
Item Load (2.2ms) SELECT DISTINCT items.id, items.*, "items".* FROM "items" WHERE "items"."id" IN (18, 20, 23, 7, 6, 30, 4, 1, 17, 5, 15, 12, 9, 29, 10, 19, 3, 8, 13) ORDER BY items.created_at DESC
ItemCategory Load (0.5ms) SELECT "item_categories".* FROM "item_categories" WHERE "item_categories"."id" IN (4, 6, 2, 1, 3, 7)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (1.2ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.1ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (2.8ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (1.4ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.9ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (1.2ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.3ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.9ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (2.7ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.8ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.7ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (1.2ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (1.1ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.3ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (2.2ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.8ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.3ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (3.4ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.3ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.0ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (2.6ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.3ms)
Rendered outfits/_other_users_outfit_secondary_item.html.haml (0.3ms)
Rendered outfits/_other_users_outfit_primary_item.html.haml (2.1ms)
Rendered outfits/_other_users_outfit.html.haml (56.3ms)
(0.5ms) SELECT COUNT(*) FROM "outfits" WHERE (user_id != 3)
Rendered outfits/other_users.html.haml within layouts/application (2073.5ms)
Role Load (0.4ms) SELECT "roles".* FROM "roles" WHERE "roles"."name" = 'admin' LIMIT 1
(0.4ms) SELECT 1 FROM "roles" INNER JOIN "roles_users" ON "roles"."id" = "roles_users"."role_id" WHERE "roles_users"."user_id" = 3 AND "roles"."id" = 1 LIMIT 1
Rendered layouts/_top_nav.html.haml (1.0ms)
(0.6ms) SELECT COUNT(*) FROM "items" WHERE "items"."user_id" = 3
Rendered layouts/_points_display.html.haml (5.7ms)
Outfit Load (0.6ms) SELECT DISTINCT outfits.id, outfits.* FROM "outfits" WHERE "outfits"."user_id" = 3 ORDER BY outfits.created_at DESC
OutfitCategory Load (0.3ms) SELECT "outfit_categories".* FROM "outfit_categories"
.
Any help would be much appreciated!
The only thing I see that could stand improvement is the code in the helper. Is there a reason why you're doing this:
def outfit_item_in_category(outfit, cat_name)
outfit.items.select{|item| item.category.name == cat_name }.first
end
instead of pushing this code to a scope in the Item model? If you have a lot of items, you're basically doing a SELECT * on them and then filtering in Ruby.