discourse/db/migrate/20190424065841_add_post_image_indexes.rb

# frozen_string_literal: true

class AddPostImageIndexes < ActiveRecord::Migration[5.2]
  def change
    %w[large_images broken_images downloaded_images].each do |field|
      execute <<~SQL
        DELETE FROM post_custom_fields f
        WHERE name = '#{field}' AND id > (
          SELECT MIN(f2.id) FROM post_custom_fields f2
            WHERE f2.post_id = f.post_id AND f2.name = f.name
        )
      SQL

      add_index :post_custom_fields,
                [:post_id],
                name: "post_custom_field_#{field}_idx",
                unique: true,
                where: "name = '#{field}'"
    end
  end
end