The class origins back to a sidekiq worker class, so the implementation might not be ideal for stand ole usage, but I think you see the point...

reindex_concurrenty.rb

class DailyReindexingJob

  #
  # Reindexes for performance reasons
  #
  def perform
    tables_to_be_reindexed.each do |tbl|
      indexes_for(tbl).each do |idx|

        idx_name = idx['relname']

        tmp_new_idx_name = random_index_name
        tmp_old_idx_name = random_index_name

        raise "The two tmp_idx names '#{tmp_new_idx_name}' and '#{tmp_old_idx_name}' may not be the same!" if tmp_new_idx_name == tmp_old_idx_name
        
        create_statement = idx['pg_get_indexdef'].gsub('INDEX ', 'INDEX CONCURRENTLY ').gsub(idx_name, tmp_new_idx_name)

        begin
          create_index(create_statement)
          rename_indexes(idx_name, tmp_old_idx_name, tmp_new_idx_name)
        ensure
          drop_indexes([tmp_old_idx_name, tmp_new_idx_name])
        end
      end 
    end
    return true
  end

  private

  def tables_to_be_reindexed
    [
      "advert_candidate_collector_statuses", 
      "failed_adverts",
      "adverts",
      "cars"
    ].freeze
  end

  def indexes_for table
    ActiveRecord::Base.connection.execute("SELECT relname, pg_get_indexdef(indexrelid) FROM pg_index JOIN pg_class ON pg_class.oid = pg_index.indexrelid WHERE indisprimary = false AND indrelid ='#{current_schema}.#{table}'::regclass;")
  end

  def random_index_name
    Array.new(32) { (rand(122-97) + 97).chr }.join
  end

  def current_schema
    "public"
  end

  def create_index create_statement
    ActiveRecord::Base.connection.execute(create_statement)
  end

  def rename_indexes idx_name, tmp_old_idx_name, tmp_new_idx_name
    ActiveRecord::Base.transaction do
      ActiveRecord::Base.connection.execute("ALTER INDEX #{idx_name} RENAME TO #{tmp_old_idx_name}")
      ActiveRecord::Base.connection.execute("ALTER INDEX #{tmp_new_idx_name} RENAME TO #{idx_name}")
    end
  end

  def drop_indexes index_names
    index_names.each do |name|
      ActiveRecord::Base.connection.execute("DROP INDEX CONCURRENTLY IF EXISTS #{name}")
    end
  end

end