CODEWITHSUNDEEP
ruby-on-railspostgresqlruby-on-rails-5
Raymond Peterfellow
Raymond Peterfellow

Reputation: 634

Get user comments and all comments grouped within the same query

I'm currently working with Rails 5 and Postgresql. There's a model Post that can have many comments, through a model called PostComments, that way a comment can belong to a single post, but that post can have many comments. I'm trying to get all comments, grouped in the ones belonging to a specific user, and all other that not.

class Post < ApplicationRecord
  has_many :post_comments
  has_many :comments, through: :post_comments
  ...

class Coment < ApplicationRecord
  has_many :post_comments
  has_many :posts, through: :post_comments
  ...

Currently I'm doing two queries and comparing, like:

foo = Comment.select(:id, :description)
bar = Comment.joins(:post).select(:id, :description).where(posts: { id: post_id })
remaining_comments = [foo - bar, foo]

This gives me all comments for a specific store, and all the remaining ones, but I was wondering is there a better way on doing this?

Upvotes: 0

Views: 191

Answers (2)

Shiko
Shiko

Reputation: 2624

You can get the comments in one query like below: 

@comments = Comment.left_outer_joins(:post)
                   .select("comments.id,comments.description,posts.id as post_id")
                   .where("posts.id = ? OR posts.id IS NULL",  post_id })

Then split using group_by: 

remaining_comments = @comments.group_by(&:post_id)

Upvotes: 2

Yuri Gert
Yuri Gert

Reputation: 103

If I'm interpreting you correctly, you're trying to efficiently get an array of PostComments that do not belong to a particular Post?

If this is the case, simply use the not method:

x = # given Post id
post = Post.find(x).id
postcomments = PostComment.where.not(post_id: post)

Upvotes: 1

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