transactor.hxx

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/* Transactor framework, a wrapper for safely retryable transactions.
 *
 * DO NOT INCLUDE THIS FILE DIRECTLY; include pqxx/transactor instead.
 *
 * Copyright (c) 2000-2026, Jeroen T. Vermeulen.
 *
 * See COPYING for copyright license.  If you did not receive a file called
 * COPYING with this source code, please notify the distributor of this
 * mistake, or contact the author.
 */
#ifndef PQXX_TRANSACTOR_HXX
#define PQXX_TRANSACTOR_HXX
 
#if !defined(PQXX_HEADER_PRE)
#  error "Include libpqxx headers as <pqxx/header>, not <pqxx/header.hxx>."
#endif
 
#include <functional>
#include <type_traits>
 
#include "pqxx/connection.hxx"
#include "pqxx/transaction.hxx"
 
namespace pqxx
{
 
 
template<typename TRANSACTION_CALLBACK>
inline std::invoke_result_t<TRANSACTION_CALLBACK> perform(
  TRANSACTION_CALLBACK &&callback, int attempts = 3, sl loc = sl::current())
{
  if (attempts <= 0)
    throw std::invalid_argument{
      "Zero or negative number of attempts passed to pqxx::perform()."};
 
  for (; attempts > 0; --attempts)
  {
    try
    {
      return std::invoke(callback);
    }
    catch (in_doubt_error const &)
    {
      // Not sure whether transaction went through or not.  The last thing in
      // the world that we should do now is try again!
      throw;
    }
    catch (statement_completion_unknown const &)
    {
      // Not sure whether our last statement succeeded.  Don't risk running it
      // again.
      throw;
    }
    catch (insufficient_resources const &)
    {
      // Server is being overloaded.  Back off.
      throw;
    }
    catch (too_many_connections const &)
    {
      // Server is being overloaded.  Back off.
      throw;
    }
    catch (failure const &)
    {
      // Some other database-related failure.  Retry, unless we've run out of
      // attempts.
      if (attempts <= 1)
        throw;
    }
  }
  throw internal_error{"Reached unreachable transactor state.", loc};
}
 
 
template<typename TRANSACTION_CALLBACK>
[[deprecated("No soruce_location needed.")]] inline std::invoke_result_t<
  TRANSACTION_CALLBACK>
perform(TRANSACTION_CALLBACK &&callback, sl loc)
{
  return perform(std::forward(callback), 3, loc);
}
} // namespace pqxx
#endif