Rails read Postgres database column comments

database_comment.rb

# frozen_string_literal: true
# A tiny class for reading column database comments
class DatabaseComment
  DATABASE_NAME = Rails.configuration.database_configuration[Rails.env]['database'].freeze

  # Reads back a postgres comment based on table_name and column_name
  # Sanitizes inputs but it would be better not to allow user input strings here regardless
  def self.read(table_name, column_name)
    unless table_name.is_a?(Symbol) && column_name.is_a?(Symbol)
      raise TypeError, <<~STERN_WARNING
        Table and column names must be symbols.
        If you are trying to pass strings input by a user, well, please don't do that."
      STERN_WARNING
    end

    quoted_table_name = ActiveRecord::Base.connection.quote_table_name(table_name)
    table_name = ActiveRecord::Base.connection.quote(table_name)
    column_name = ActiveRecord::Base.connection.quote(column_name)
    select_comment = <<~SQL
      SELECT col_description(
        (select distinct tableoid from #{quoted_table_name}),
        (SELECT ordinal_position
         FROM   information_schema.columns
         WHERE  table_catalog = 'progolfme_development'
           AND column_name = #{column_name}
           AND table_name = #{table_name})
      )
    SQL

    ActiveRecord::Base.connection.execute(select_comment).to_a.dig(0, 'col_description')
  end
end

Requires Ruby >= 2.3 unless you remove the squiggly heredocs.