I am using
MongoId 5.4
Rails 4.2
Want to perform join operation and retrieve the result based on criteria.
Band Table
has_many :band_histories, dependent: :destroy
field :name, type: String
field :description, type: String
Band History
belongs_to :band, foreign_key: :band_id
field :subject, type: String
field :status, type: String
I want to add make a search on Band history where band name is 'Star band'
Normal Query Can be Made like
BandHistory.where(: band_id.in => Band.where(name: 'Star band').pluck(:id))
Trying to use includes to make it more generic
BandHistory.includes(:band).where('bands.name':'Star band').count
Above include and where clause is not returning any result
Can anyone help where i am doing wrong
Related
I have an application where users can create many travels, and they can invite their facebook friends. In the travel document, there is a field "participants" that is an embedded document, Participant model embedded in Travel model.
Here are my models :
class Travel
include Mongoid::Document
include Mongoid::Timestamps
# relations
belongs_to :user
# fields
field :title, type: String
field :description, type: String
field :begin_date, type: Date
field :end_date, type: Date
field :budget, type: Integer
field :go_back, type: Boolean
field :title_namespace, type: String
# friends
embeds_many :participants
accepts_nested_attributes_for :participants
end
class Participant
include Mongoid::Document
include Mongoid::Timestamps
field :name, type: String
field :user_id, type: String
# relations
embedded_in :travel, :inverse_of => :participants
end
When I try to display travel where users have been invited, with this request :
#travel_participations = Travel.where('participants.user_id' => #user.id)
I don't have any result, even if I have this line in byebug :
#<Mongoid::Criteria
selector: {"participants.user_id"=>BSON::ObjectId('592c8da58511989ec850921e')}
options: {}
class: Travel
embedded: false>
So when I put this on my view :
<% unless #participations.nil? %>
<% #travel_participations.each do |travel_participation| %>
<p> <%= travel_participation.title %> </p>
<% end %>
<% end %>
I tried with .all, .first, .to_a, .as_json, no results ... Some one know where is the problem ?
You have this in your embedded model:
field :user_id, type: String
but your query is using a BSON::ObjectId:
Travel.where('participants.user_id' => #user.id)
as shown in the raw query:
selector: {"participants.user_id"=>BSON::ObjectId('592c8da58511989ec850921e')}
Your embedded document probably has a string field like:
"user_id": "592c8da58511989ec850921e"
rather than the ObjectId you're looking for:
"user_id": ObjectId("592c8da58511989ec850921e")
so you won't find what you're looking for due to the type mismatch.
Either fix the embedded field's type:
field :user_id, type: BSON::ObjectId
or query it as the string it is:
Travel.where('participants.user_id' => #user.id.to_s)
Changing the type will involve fix up whatever data you already have, changing the query is ugly in a different way.
Sometimes Mongoid will convert between strings and ObjectIds for you, sometimes it won't. When I used Mongoid I patched to_bson_id methods into BSON::ObjectId, String, Mongoid::Document, ... so that I could say things like:
Model.where(:some_id => some_id.to_bson_id)
and not have to constantly worry about what type some_id was. I also made sure that all ID fields were always specified as BSON::ObjectId.
I'd like to pull all companies that have at least one position title of "CEO".
I could hack it together with a query for each table and an intersect (I know... no joins http://mongoid.org/en/mongoid/docs/tips.html#relational_associations, and N+1 problem in mongoid, and I could just embed positions in company), but any way to do something like:
Company.includes(:positions).where("positions.title" => "CEO")?
Thanks:
class Position
include Mongoid::Document
field :title, type: String
field :profile_id, type: String
field :tenure, type: BigDecimal
belongs_to :company, index: true
class Company
include Mongoid::Document
field :name, type: String
field :linkedin_id, type: String
field :positions_count, type: Integer #Mongo Index
belongs_to :industry, index: true
has_many :positions
index({ positions_count: 1}, {background: true})
To avoid the the N+1 problem enable Mongoid identity_map feature
This will allow you to do the following query:
companies_with_ceo = Position.where(title: 'CEO').includes(:company).map(&:company)
Which should execute only 2 queries to the database.
I'm having some problems trying to understand how Mongoid does its sorting. I have 2 models, Gig and Venue, both of which are associated by a belong_to has_many relationship.
I'm trying to sort objects from Gig by the attribute 'name' of the Venue Object to no avail.
I'm hoping someone out there would be able to point me to the right direction.
Below are a truncated model description.
My Query is also below:
# Gig Model
class Gig
include Mongoid::Document
include Mongoid::Paperclip
include SearchMagic
belongs_to :owner, :class_name => "User", :inverse_of => :owns
belongs_to :venue
has_and_belongs_to_many :attenders, :class_name => "User", :inverse_of => :attending
has_and_belongs_to_many :artistes
<snip>
end
# Venue Model
class Venue
include Mongoid::Document
include Mongoid::Paperclip
include SearchMagic
has_many :gigs
field :foursquare_id, type: String
embeds_one :address
embeds_many :user_ratings
field :facebook, type: String
field :twitter, type: String
field :website, type: String
field :name, type: String
field :postal, type: String
field :tel, type: String
field :venue_type, type: String
field :description, type: String
field :rating, type: Float, default: 0.0
<snip>
end
# Console
>> Gig.desc('venue.name').map{|f| f.venue.name}
=> ["*SCAPE", "Velvet Underground", "Blujaz Lounge", "Velvet Underground", "Home Club", "Wh
ite House, Emily Hill", "Zouk", "Zouk", "The Pigeonhole", "Home Club", "Home Club", "Home C
lub"]
# sorting doesn't work
You can't join in mongo. If you need joins, use a relational database. A "feature" of non-relational databases is that you can't do joins.
You have basically two choices:
a before_save callback, which will inject the name of the venue into the gig as an additional field (see for instance https://github.com/rewritten/timebank/blob/master/lib/mongoid/denormalize.rb)
a map-reduce task, which after any modification of any venue or gig, will update the venue name into the gig as an additional field.
In the end, you need a field in the Gig collection to order it.
I want to query with mongoid , I have following models
class Score
include Mongoid::Document
field :value, :type => Integer
belongs_to :user
end
class User
include Mongoid::Document
field :name, :type => String
field :age, :type => Integer
has_many :scores
I want to query all the scores from collection with their users. but users object should have only have the 'name' field in it
I would be something like
Score.find.all.includes(:user).only(:name)
Please tell the correct syntax for this
Score references User, so it is not possible to retrieve them both in one query, because there are no joins in MongoDB.
Either denormalize and include user name in Score or do several queries.
Im newbee in mongoid and I have two basic (I think) questions. Whats best way to store array of references in Mongoid. Here is a short example what I need (simple voting):
{
"_id" : ObjectId("postid"),
"title": "Dummy title",
"text": "Dummy text",
"positive_voters": [{"_id": ObjectId("user1id")}, "_id": ObjectId("user2id")],
"negative_voters": [{"_id": ObjectId("user3id")}]
}
And its a right way?
class Person
include Mongoid::Document
field :title, type: String
field :text, type: String
embeds_many :users, as: :positive_voters
embeds_many :users, as: :negative_voters
end
Or its wrong?
Also Im not sure, maybe its a bad document structure for this situation? How can i gracefully get if user already voted and dont allow users vote twice? Maybe I should use another structure of document?
Rather than embeds_many you can go for has_many because you just want to save the reference of voters in the document rather than saving whole user document in person
class Person
include Mongoid::Document
field :title, type: String
field :text, type: String
has_many :users, as: :positive_voters
has_many :users, as: :negative_voters
validate :unique_user
def unique_user
return self.positive_voter_ids.include?(new_user.id) || self.negative_voter_ids.include?(new_user.id)
end
end