discourse/app/models/reports/posts.rb

# frozen_string_literal: true

Report.add_report('posts') do |report|
  report.modes = [:table, :chart]

  category_id, include_subcategories = report.add_category_filter

  basic_report_about report, Post, :public_posts_count_per_day, report.start_date, report.end_date, category_id, include_subcategories

  countable = Post.public_posts.where(post_type: Post.types[:regular])
  if category_id
    if include_subcategories
      countable = countable.joins(:topic).where('topics.category_id IN (?)', Category.subcategory_ids(category_id))
    else
      countable = countable.joins(:topic).where('topics.category_id = ?', category_id)
    end
  end

  add_counts report, countable, 'posts.created_at'
end