void *connect(void* threadid)
{
char command[100];
int *id_ptr, taskid;
id_ptr = (int *) threadid;
taskid = *id_ptr;
if(taskid == 0)
strcpy(command, "select insert (1)");
else if(taskid == 1)
strcpy(command, "select insert (1)");
else if(taskid == 2)
strcpy(command, "select insert (3)");
else if(taskid == 3)
strcpy(command, "select insert (4)");
else if(taskid == 4)
strcpy(command, "select insert (5)");
PGconn *conn = connect("dbname=x host=y user=z");
pgresult res;
res = pqexec (conn, "begin transaction");
res = pqexec (conn, command);
res = pqexec (conn, "commit");
pqfinish (conn);
pthread_exit(NULL);
}
int main()
{
pthread_t threads[NUM_THREADS];
int rc;
int *taskids[NUM_THREADS];
for(int t=0; t<NUM_THREADS; t++)
{
taskids[t] = (int *) malloc(sizeof(int));
*taskids[t] = t;
rc = pthread_create(&threads[t], NULL, connect, (void *) taskids[t]);
if (rc)
{
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
}
for(int t=0; t<NUM_THREADS; t++)
{
delete taskids[t];
}
pthread_exit(NULL);
}
the stored procedure (just the pseudo code)
table x has a primary key k
insert(integer)
{
select from table if k = $1
if not found
insert into x ($1);
else
insert into some_other_table($1);
end if
}
the kind of output i am expecting is:
table x: 1 3 4 5
table a: 1
and no error message
but the output is something like
table x : 1 3 4 5
table some_other_table :
it has nothing
and error message is displayed : "error in stored proc "insert(..... primary key violation .."
this error is because
two threads are simultaneoulsy trying to insert the values "1" each and thats where they interfere with each other.
thanks
surabhi ahuja