select_value

# File activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb, line 10
        def select_value(arel, name = nil, binds = [])
          arel, binds = binds_from_relation arel, binds
          sql = to_sql(arel, binds)
          execute_and_clear(sql, name, binds) do |result|
            result.getvalue(0, 0) if result.ntuples > 0 && result.nfields > 0
          end
        end