BUG #1569: Threads don't see ecpg default connection

The following bug has been logged online:

Bug reference:      1569
Logged by:          Gavin Scott
Email address:      gavin@ipalsoftware.com
PostgreSQL version: 8.0.1
Operating system:   Fedora Core 3
Description:        Threads don't see ecpg default connection
Details:

When using postgresql 8.0 compiled with --enable-thread-safety, new threads
no longer see the default ecpg connection.  That was not the case in 7.4.x
compiled with or without --enable-thread-safety.

TEST CASE

The program at the end of this mail sets up a database table named
"dbthreadtest" in the default database.  It then spawns 5 threads which each
do a select from that table using the default connection.

If the program is saved as dbthreadtest.pgc, compile with:

ecpg -t -o dbthreadtest.c dbthreadtest.pgc
gcc -Wall -o dbthreadtest dbthreadtest.c -lecpg -lpthread

Results under 7.4.x / 8.0 without --enable-thread-safety:

[gavin@hesse protocol_lib]$ psql --version
psql (PostgreSQL) 7.4.7
contains support for command-line editing
[gavin@hesse protocol_lib]$ ./dbthreadtest
got id = 1
got id = 1
got id = 1
got id = 1
got id = 1

Results under 8.0 with --enable-thread-safety:

[gavin@marquez protocol_lib]$ psql --version
psql (PostgreSQL) 8.0.1
contains support for command-line editing
[gavin@marquez protocol_lib]$ ./dbthreadtest
'No such connection NULL in line 76.', sqlcode = -220 select id

TEST PROGRAM

/* -*-C-*- */

#include <stdlib.h>
#include <pthread.h>

#define CHECK_SQL(fmt, args...)                \
do                            \
{                            \
  if (sqlca.sqlcode != ECPG_NO_ERROR)            \
    {                            \
      fprintf (stderr, "'%s', sqlcode = %ld " fmt "\n",    \
           sqlca.sqlerrm.sqlerrmc,            \
           sqlca.sqlcode, ## args);            \
      exit (1);                        \
    }                            \
 }                            \
while (0)

#define FATAL(fmt, args...)            \
do                        \
{                        \
  fprintf (stderr, fmt "\n", ## args);        \
  exit (1);                    \
}                        \
while (0)

pthread_mutex_t global_lock;
pthread_t global_threads[5];

void
setup_db ()
{
  exec sql begin declare section;
    const char *_user;
  exec sql end declare section;

  pthread_mutex_lock (&global_lock);

  _user = getenv ("LOGNAME");

  exec sql connect to :_user;
  CHECK_SQL ("connect");

  exec sql create table dbthreadtest (id int);
  CHECK_SQL ("create dbthreadtest");

  exec sql insert into dbthreadtest (id) values (1);
  CHECK_SQL ("insert 1");

  pthread_mutex_unlock (&global_lock);
}

void
teardown_db ()
{
  pthread_mutex_lock (&global_lock);

  exec sql drop table dbthreadtest;
  CHECK_SQL ("drop dbthreadtest");

  exec sql disconnect;
  CHECK_SQL ("disconnect");

  pthread_mutex_unlock (&global_lock);
}

void *query_db (void *ignorep)
{
  exec sql begin declare section;
    int _id;
  exec sql end declare section;

  pthread_mutex_lock (&global_lock);
  exec sql select id into :_id from dbthreadtest;
  CHECK_SQL ("select id");

  fprintf (stdout, "got id = %d\n", _id);
  pthread_mutex_unlock (&global_lock);

  return NULL;
}

int
main ()
{
  int i;

  pthread_mutex_init (&global_lock, NULL);

  setup_db ();

  for (i = 0; i < sizeof (global_threads) / sizeof (global_threads[0]);
++i)
    {
      if (pthread_create (&global_threads[i], NULL, query_db, NULL))
    FATAL ("pthread_create %d failed", i);
    }

  for (i = 0; i < sizeof (global_threads) / sizeof (global_threads[0]);
++i)
    {
      if (pthread_join (global_threads[i], NULL))
    FATAL ("pthread_join %d failed", i);
    }

  teardown_db ();

  return 0;
}