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Asked: 2026-05-11T05:21:09+00:00

I’m trying to write an ActiveRecord find query with no success. Please help! This

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I’m trying to write an ActiveRecord find query with no success. Please help!

This feature of my project is kind of a blog with Digg-like features: each registered user can add a star to the blog post itself or any of its replies.

So here are the relevant model classes:

  • BlogPost (has_many Replies)
  • Reply (belongs_to Blog Post)
  • Starring (this represents the action of one users starring one BlogPost or Reply; it has a polymorphic interface to BlogPost and Reply, referring to them internally as :starrables, replete with :starrable_id and :starrable_type fields)

So, what I am trying to do is write a method in blog_post.rb that will return the total number of starrings for the BlogPost object as well as all of its Reply classes. That is, if a blog post has 10 stars, and it has two replies which each have 5 stars, it should return 20.

How do I write this query without making a jillion database transactions?

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1 Answer

  1. I would suggest doing it with SQL. You can do it several ways. Are you using MYSQL? If you want to do with with 2 queries and then add the numbers together you can do something like this in SQL:

    select count(starrings.id) from starrings where starrable_type='BlogPost' and starrable_id=#{blogpost.id}

    and

    select count(starrings.id) from starrings join replies on starrings.starrable_type='Reply' and starrable_id=replies.id and replies.blog_post_id=#{blogpost.id}

    Note: I didn’t test this SQL and may have misspelled something or made a typo.

    You can run SQL counts with ‘Starring.count_by_sql(your sql here)’ then add the 2 numbers together. You can probably get this down to 1 SQL statement with a union, but I wouldn’t bother.

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