ActiveRecord Rails 4.2 - Filter includes request

I am trying to improve some queries in my Rails 4.2 project. One request, in particular, is done in an API controller. The request looks like this (as an example):

@books = Book.includes(:pages).where( category_id: 1 )

      

        
        
        
      

    

This creates the following SQL:

SELECT "books".* FROM "books" WHERE "books".category_id = 1

SELECT "pages".* FROM "pages" WHERE "pages"."book_id" IN (1, 2, 3)

      

        
        
        
      

    

That's good, it behaves just fine on the database side.

Then suppose I need to filter books based on a page attribute. The request will be something like this:

@books = Book.includes(:pages).where( category_id: 1, pages: { attr1: 'bar' } )

      

        
        
        
      

    

This creates the following SQL:

SELECT "books".attr1, "books".attr2, "pages".attr1, "pages".attr2
FROM "books"
    LEFT OUTER JOIN "pages" ON "books".id = "pages".book_id
WHERE "books".category_id = 1 AND "pages".attr1 = 'bar';

      

        
        
        
      

    

This isn't necessarily a bad thing. However, I would like to have the following SQL instead:

SELECT "books".* FROM "books" WHERE "books".category_id = 1

SELECT "pages".* FROM "pages" WHERE "pages"."book_id" IN (1, 2, 3) AND "pages".attr1 = 'bar'

      

        
        
        
      

    

You see, it's easier to create indexes for each individual query in the database.

Is there a way that I can achieve what I want?

Thank.

PS: Please excuse any typo in the written code.