Mongo ids leads to scary URLs - mongodb

This might sound like a trivial question, but it is rather important for consumer facing apps
What is the easiest way and most scalable way to map the scary mongo id onto a id that is friendly?
xx.com/posts/4d371056183b5e09b20001f9
TO
xx.com/posts/a
M

You can create a composite key in mongoid to replace the default id using the key macro:
class Person
include Mongoid::Document
field :first_name
field :last_name
key :first_name, :last_name
end
person = Person.new(:first_name => "Syd", :last_name => "Vicious")
person.id # returns "syd-vicious"
If you don't like this way to do it, check this gem: https://github.com/hakanensari/mongoid-slug

Define a friendly unique field (like a slug) on your collection, index it, on your model, define to_param to return it:
def to_param
slug
end
Then in your finders, find by slug rather than ID:
#post = Post.where(:slug => params[:id].to_s).first
This will let you treat slugs as your effective PK for the purposes of resource interaction, and they're a lot prettier.

Unfortunately, the key macro has been removed from mongo. For custom ids,
users must now override the _id field.
class Band
include Mongoid::Document
field :_id, type: String, default: ->{ name }
end

Here's a great gem that I've been using to successfully answer this problem: Mongoid-Slug
https://github.com/digitalplaywright/mongoid-slug.
It provides a nice interface for adding this feature across multiple models. If you'd rather roll your own, at least check out their implementation for some ideas. If you're going this route, look into the Stringex gem, https://github.com/rsl/stringex, and acts_as_url library within. That will help you get the nice dash-between-url slugs.

Related

How to filter fields from the database in JSON response?

i am making a REST API in golang and i want to add support for filtering fields but i don't know the best way to implement that, lets say i have this structure representing an Album model
type Album struct {
ID uint64 `json:"id"`
User uint64 `json:"user"`
Name string `json:"name"`
CreatedDate time.Time `json:"createdDate"`
Privacy string `json:"privacy"`
Stars int `json:"stars"`
PicturesCount int `json:"picturesCount"`
}
and a function that returns an instance of an Album
func GetOne(id uint64, user uint64) (Album, error) {
var album Album
sql := `SELECT * FROM "album" WHERE "id" = $1 AND "user" = $2;`
err := models.DB.QueryRow(sql, id, user).Scan(
&album.ID,
&album.User,
&album.Name,
&album.CreatedDate,
&album.Privacy,
&album.Stars,
&album.PicturesCount,
)
return album, err
}
and the client was to issue a request like this
https://api.localhost.com/albums/1/?fields=id,name,privacy
obvious security issues aside, my first thought was to filter the fields in the database using something like this
func GetOne(id uint64, user uint64, fields string) {
var album Album
sql := fmt.Sprintf(`SELECT %s FROM "album" WHERE "id" = $1 AND "user" = $2;`, fields)
// i don't know what to do after this
}
and then i thought of adding omitempty tag to all the fields and setting the fields to their zero value before encoding it to JSON,
would this work?
which one is the better way?
is there a best way?
how would i go about implementing the first method?
Thank you.
For your first proposal (querying only the requested fields) there are two approaches (answering "would this work?" and "how would I go about implementing the first method?"):
Dynmaically reate a (possibly anonymous) struct and generate JSON from there using encoding/json.
Implement a wrapper that will translate the *database/sql.Rows you get back from the query into JSON.
For approach (1.), you will somehow need to create structs for any combination of attributes from your original struct. As reflect cannot create a new struct type at runtime, your only chance would be to generate them at compile time. The combinatorial explosion will bloat your binary, so do not do that.
Approach (2.) is to be handled with caution and can only be a last resort. Taking the list of requested fields and writing out JSON with the values you got from DB sounds straightforward and does not involve reflection. However your solution will be (very likely) much more unstable than encoding/json.
When reading your question I too thought about using the json:"omitempty" struct tag. And I think that it is the preferable solution. It does neither involve metaprogramming nor writing your own JSON encoder, which is a good thing. Just be aware of the implications in case some fields are missing (client side maybe has to account for that). You could query for all attributes always and override the unwanted ones using reflection.
In the end, all above solutions are suboptimal, and the best solution would be to not implement that feature at all. I hope you have a solid reason to make attributes variable, and I am happy to further clarify my answer based on your explaination. However, if one of the attributes of a resource is too large, it maybe should be a sub-resource.

Though I have a record in database, it's giving "Mongoid::Errors::DocumentNotFound"

Though I have the record with id 13163 (db.locations.find({_id: 13163})), it's giving me error:
Mongoid::Errors::DocumentNotFound in LocationsController#show
Problem: Document(s) not found for class Location with id(s) 13163.
Summary: When calling Location.find with an id or array of ids, each
parameter must match a document in the database or this error will be
raised. The search was for the id(s): 13163 ... (1 total) and the
following ids were not found: 13163. Resolution: Search for an id that
is in the database or set the Mongoid.raise_not_found_error
configuration option to false, which will cause a nil to be returned
instead of raising this error when searching for a single id, or only
the matched documents when searching for multiples.
# Use callbacks to share common setup or constraints between actions.
def set_location
#location = Location.find(params[:id])
end
locations_controller.rb:
class LocationsController < ApplicationController
before_action :set_location, only: [:show, :edit, :update, :destroy]
# GET /locations
# GET /locations.json
def index
#locations = Location.all
end
# GET /locations/1
# GET /locations/1.json
def show
end
private
# Use callbacks to share common setup or constraints between actions.
def set_location
#location = Location.find(params[:id])
end
# Never trust parameters from the scary internet, only allow the white list through.
def location_params
params.require(:location).permit(:loc_name_en, :loc_name_jp, :channel)
end
end
Setting up the option raise_not_found_error: false is not the case as I do have a document in database.
SOLUTION:
Big thanks to #mu is too short for giving me a hint.
The problem can be solved in 2 ways:
Declare field :_id, type: Integer in the model location.rb
Or converting the passing parameter to Integer like Location.find(params[:id].to_i) in locations_controller.rb as shown below in the #mu is too short's answer
I'd guess that you have a type problem. You say that this:
db.locations.find({_id: 13163})
finds the document in the MongoDB shell. That means that you have a document in the locations collection whose _id is the number 13163. If you used the string '13163':
db.locations.find({_id: '13163'})
you won't find your document. The value in params[:id] is probably a string so you're saying:
Location.find('13163')
when you want to say:
Location.find(13163)
If the _id really is a number then you'll need to make sure you call find with a number:
Location.find(params[:id].to_i)
You're probably being confused because sometimes Mongoid will convert between Strings and Moped::BSON::ObjectIds (and sometimes it won't) so if your _id is the usual ObjectId you can say:
Model.find('5016cd8b30f1b95cb300004d')
and Mongoid will convert that string to an ObjectId for you. Mongoid won't convert a String to a number for you, you have to do that yourself.

MongoMapper issue with stack level being too deep

Just want to start off by saying I did google this topic at length and was unable to find anything that applied to my own use case.
I have a simple little ad server. There is a model for Ad, and two embedded models called Impression and Click - like so:
class Ad
include MongoMapper::Document
key :name, String
key :image, String
key :url, String
has_many :clicks
has_many :impressions
end
class Click
include MongoMapper::EmbeddedDocument
key :ip, String
timestamps!
end
class Impression
include MongoMapper::EmbeddedDocument
key :ip, String
timestamps!
end
And here is the error I'm getting:
SystemStackError - stack level too deep:
/home/deployer/.rbenv/versions/1.9.3-p125/lib/ruby/gems/1.9.1/gems/mongo_mapper-0.12.0/lib/mongo_mapper/plugins/keys.rb:194
Here is the area that this is happening in:
#ad.impressions << Impression.new({:ip => request.ip})
#ad.save
Now, I do not have any callbacks here in my models, which is the reason this error happens for a lot of people.
Anyone have any insights?
Thanks.
I seem to have hit on the answer. the timestamps! is what was causing this. The other examples I saw online had to do with callbacks and the way that ActiveSupport runs them. I just didn't realize that timestamps! counts as one.

Mongoid, find object by searching by part of the Id?

I want to be able to search for my objects by searching for the last 4 characters of the id. How can I do that?
Book.where(_id: params[:q])
Where the param would be something like a3f4, and in this case the actual id for the object that I want to be found would be:
bc313c1f5053b66121a8a3f4
Notice the last for characters are what we searched for. How can I search for just "part" of my objects id? instead of having my user search manually by typing in the entire id?
I found in MongoDB's help docs, that I can provide a regex:
db.x.find({someId : {$regex : "123\\[456\\]"}}) // use "\\" to escape
Is there a way for me to search using the regular mongo ruby driver and not using Mongoid?
Usually, in Mongoid you can search with a regexp like you normally would with a string in your call to where() ie:
Book.where(:title => /^Alice/) # returns all books with titles starting with 'Alice'
However this doesn't work in your case, because the _id field is not stored as a string, but as an ObjectID. However, you could add (and index) a field on your models which could provide this functionality for you, which you can populate in an after_create callback.
<shameless_plug>
Alternatively, if you're just looking for a shorter solution to the default Mongoid IDs, I could suggest something like mongoid_token which makes it pretty easy to add shorter tokens/ids to your Mongoid documents.
</shameless_plug>

Embedded and no-embedded document in the same time

I need to have a model which will behave like a embedded and not-embedded.
For example if I want to store this model as embedded:
class MenuPosition
include Mongoid::Document
field :name, type: String
field :category, type: String
I need to add
embedded_in :menu
to it.
On the other side, if I add this line in the model I cannot store this model as not-embedded:
position = {
"name" => "pork",
"category" => "meal",
"portion" => 100
}
MenuPosition.create(position)
error message:
NoMethodError:
undefined method `new?' for nil:NilClass
Can I use one model for embedded and not-embedded documents?
In our project we had a similar thing. What we did is define the fields as a module. A bit like this:
module SpecialFields
extend ActiveSupport::Concern
included do
field :my_field, type: String
field :my_other_field, type: String
end
end
Then in your class where you want to embed, just do:
include SpecialFields
In your class that you'd like to store separately as a non-embedded document, do this:
class NotEmbeddedDoc
include Mongoid::Document
include SpecialFields
end
This worked pretty well in our project for a few things. However, it might not be appropriate in your case since you want to embed many. This only really works for embeds one cases I think. I have posted it here in case it helps people.