Postgresql and libpq . Query getting dropped from randrom number of child processes

Question

I have forked 4 client process from parent. For testing purpose, i execute an sql query in the child process when i receive valid input.

My debug show that i received the valid string in all the child process. In most cases, PQsendquery is sent out. Epoll receives notification that postgres replied but not sure what i am doing wrong in consuming the PQResult.

Would anyone be kind enough to point to me where is my mistake. Thank you very much.

  if(ttlevents[i].data.fd == pgsock)
  {
    while(1)
    {
      int rc = PQconsumeInput(conn);
      if(rc != 0)
      {
        if(PQisBusy(conn) == 0)
        {
          while((result = PQgetResult(conn)) != NULL)
          {
            if(PQresultStatus(result) == PGRES_TUPLES_OK)
            {
              int nFields = PQnfields(result);
              char rowdata[1024];
              for(int i=0;i<PQntuples(result);i++)
              { 
                memset(rowdata,0,sizeof(rowdata));
                for(int j=0;j<nFields;j++)
                {
                  strcat(rowdata,PQgetvalue(result,i,j));                      
                  strcat(rowdata,"|");
                }

             int fifo_count = cpushfd();
             if(fifo_count != -1)
             {
              memset(cfifo[fifo_count].buffer,0,sizeof(cfifo[fifo_count].buffer));      
               memcpy(cfifo[fifo_count].buffer,rowdata,sizeof(rowdata));
             }
        }//for
      }
      else
      {
        printf("ERROR PGSOCK\n");
      }
         PQclear(result);
        }//While
      break; //THIS BREAK WAS MISPLACED AT THE BOTTOM EARLIER.
          PQclear(result);
         }//isBusy
       }//rc!=0
  }//While 

  write(c2p_var,stflag,sizeof stflag); 
 } // == pgsock

Does each process have its own database connection or are they sharing one? In the latter case they cannot launch concurrent queries. — Laurenz Albe, Nov 18 '19 at 07:12
Can you fix the indentation of your code so that it becomes readable? — Laurenz Albe, Nov 18 '19 at 07:23

score 0 · Answer 1 · answered Nov 19 '19 at 02:03

0

The above code is the working version. Earlier i misplaced the "break" at the bottom before outer while. Now i have placed it after the inner WHILE.

Thanks Laurenz Albe for the feedback. I found the error while doing the indentation.

answered Nov 19 '19 at 02:03

Saravanakumar Thevar

61
7

Postgresql and libpq . Query getting dropped from randrom number of child processes

1 Answers1