QThread and QDataTable

[ederbs]

I have one Form1 that it needs update immediate, when somebody I inserted some data in the DB automatically this data must appear in the Form1 of the user.

For this I am using the events NOTIFY / LISTEN of PostgreSQL and QThreads.

More I am having difficulties to give refresh in the screen.

they observe the code.

/////////////// thread.h ///////////////////////////////
#ifndef THREAD_H
#define THREAD_H
 
#include <qthread.h>
 
class Thread : public QThread
{
public:
    Thread();    
 
     virtual void backSqlThreadStart();
 
    virtual void run();
    virtual void stop();
 
private:    
    volatile bool stopped;
};
#endif

/////////////// thread.h ///////////////////////////////
#ifndef THREAD_H
#define THREAD_H

#include <qthread.h>

class Thread : public QThread
{
public:
    Thread();    
    
     virtual void backSqlThreadStart();
    
    virtual void run();
    virtual void stop();
    
private:    
    volatile bool stopped;
};
#endif

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------------------------------------------------------------------------------

/////////////// thread.cpp ///////////////////////////////
extern "C" {
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/time.h>
#include "libpq-fe.h"
}
 
#include "thread.h"
 
Thread::Thread()
{
    stopped = false;
}
 
static void exit_nicely(PGconn *conn)
{
        PQfinish(conn);        
}
 
void Thread::backSqlThreadStart()
{            
       const char *conninfo;
        PGconn     *conn;
        PGresult   *res;
        PGnotify   *notify;
        int  nnotifies;
 
        conninfo = "dbname = developers";
 
        /* Make a connection to the database */
        conn = PQconnectdb(conninfo);
 
        /* Check to see that the backend connection was successfully made */
        if (PQstatus(conn) != CONNECTION_OK)
        {
                fprintf(stderr, "Connection to database '%s' failed.\n", PQdb(conn));
                fprintf(stderr, "%s", PQerrorMessage(conn));
                exit_nicely(conn);
        }
 
        /*
         * Issue LISTEN command to enable notifications from the rule's NOTIFY.
         */
        res = PQexec(conn, "LISTEN TBL2");
        if (PQresultStatus(res) != PGRES_COMMAND_OK)
        {
                fprintf(stderr, "LISTEN command failed: %s", PQerrorMessage(conn));
                PQclear(res);
                exit_nicely(conn);
        }
 
        /*
         * should PQclear PGresult whenever it is no longer needed to avoid
         * memory leaks
         */
        PQclear(res);
 
        /* Quit after four notifies are received. */
        nnotifies = 0;
        while (nnotifies < 200)
        {	
                /*
                 * Sleep until something happens on the connection.  We use select(2)
                 * to wait for input, but you could also use poll() or similar
                 * facilities.
                 */
                int                     sock;
                fd_set          input_mask;
 
                sock = PQsocket(conn);
 
                if (sock < 0)
                        break;                          /* shouldn't happen */
 
                FD_ZERO(&input_mask);
                FD_SET(sock, &input_mask);
 
                if (select(sock + 1, &input_mask, NULL, NULL, NULL) < 0)
                {
                        fprintf(stderr, "select() failed: %s\n", strerror(errno));
                        exit_nicely(conn);
                }
 
                /* Now check for input */
                PQconsumeInput(conn);
                while ((notify = PQnotifies(conn)) != NULL)
                {		     
                        fprintf(stderr,
                                        "ASYNC NOTIFY of server FNS2 '%s' received from backend pid %d\n",
                                        notify->relname, notify->be_pid);
                        PQfreemem(notify);
                        nnotifies++;
                }
        }
 
        fprintf(stderr, "Done.\n");
 
        /* close the connection to the database and cleanup */
        PQfinish(conn);
 
        return true;
}
 
void Thread::run()
{    
    while (!stopped)
	backSqlThreadStart();         
    stopped = false;   
 
}
 
void Thread::stop()
{
    stopped = true;
}

/////////////// thread.cpp ///////////////////////////////
extern "C" {
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/time.h>
#include "libpq-fe.h"
}

#include "thread.h"

Thread::Thread()
{
    stopped = false;
}

static void exit_nicely(PGconn *conn)
{
        PQfinish(conn);        
}

void Thread::backSqlThreadStart()
{            
       const char *conninfo;
        PGconn     *conn;
        PGresult   *res;
        PGnotify   *notify;
        int  nnotifies;

        conninfo = "dbname = developers";

        /* Make a connection to the database */
        conn = PQconnectdb(conninfo);

        /* Check to see that the backend connection was successfully made */
        if (PQstatus(conn) != CONNECTION_OK)
        {
                fprintf(stderr, "Connection to database '%s' failed.\n", PQdb(conn));
                fprintf(stderr, "%s", PQerrorMessage(conn));
                exit_nicely(conn);
        }

        /*
         * Issue LISTEN command to enable notifications from the rule's NOTIFY.
         */
        res = PQexec(conn, "LISTEN TBL2");
        if (PQresultStatus(res) != PGRES_COMMAND_OK)
        {
                fprintf(stderr, "LISTEN command failed: %s", PQerrorMessage(conn));
                PQclear(res);
                exit_nicely(conn);
        }

        /*
         * should PQclear PGresult whenever it is no longer needed to avoid
         * memory leaks
         */
        PQclear(res);

        /* Quit after four notifies are received. */
        nnotifies = 0;
        while (nnotifies < 200)
        {	
                /*
                 * Sleep until something happens on the connection.  We use select(2)
                 * to wait for input, but you could also use poll() or similar
                 * facilities.
                 */
                int                     sock;
                fd_set          input_mask;

                sock = PQsocket(conn);

                if (sock < 0)
                        break;                          /* shouldn't happen */

                FD_ZERO(&input_mask);
                FD_SET(sock, &input_mask);

                if (select(sock + 1, &input_mask, NULL, NULL, NULL) < 0)
                {
                        fprintf(stderr, "select() failed: %s\n", strerror(errno));
                        exit_nicely(conn);
                }

                /* Now check for input */
                PQconsumeInput(conn);
                while ((notify = PQnotifies(conn)) != NULL)
                {		     
                        fprintf(stderr,
                                        "ASYNC NOTIFY of server FNS2 '%s' received from backend pid %d\n",
                                        notify->relname, notify->be_pid);
                        PQfreemem(notify);
                        nnotifies++;
                }
        }

        fprintf(stderr, "Done.\n");

        /* close the connection to the database and cleanup */
        PQfinish(conn);

        return true;
}

void Thread::run()
{    
    while (!stopped)
	backSqlThreadStart();         
    stopped = false;   
   
}

void Thread::stop()
{
    stopped = true;
}

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-------------------------------------------------------------------------------

In form1 I invoke thread, and the notifications appear in the console, the problem are to bring update the QDataTable of the Form1.

As I inside make of my QThread archive to bring up to date the QDataTable of the Form1 is accurately in this part of the code.

///////////////////// thread.cpp //////////////////////////////
 /* Now check for input */
                PQconsumeInput(conn);
                while ((notify = PQnotifies(conn)) != NULL)
                {
                       /* some thing of the type */
                       //Parent->dataTable->refresh();
 
                        fprintf(stderr,
                                        "ASYNC NOTIFY of server FNS2 '%s' received from backend pid %d\n",
                                        notify->relname, notify->be_pid);
                        PQfreemem(notify);
                        nnotifies++;
                }
        }

///////////////////// thread.cpp //////////////////////////////
 /* Now check for input */
                PQconsumeInput(conn);
                while ((notify = PQnotifies(conn)) != NULL)
                {
                       /* some thing of the type */
                       //Parent->dataTable->refresh();
		     
                        fprintf(stderr,
                                        "ASYNC NOTIFY of server FNS2 '%s' received from backend pid %d\n",
                                        notify->relname, notify->be_pid);
                        PQfreemem(notify);
                        nnotifies++;
                }
        }

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-----------------------------------------------------------------

They forgive for the bad English,

Ederson.

Update! Added code tags.

[e8johan]

How come you are using PQ directly instead of through the QtSql module?

The obvious way to do what you want to do is to emit a signal to the dialog in question as soon as a change takes place.