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PGExec returns error without any comment
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* PGExec returns error without any comment
@ 2006-09-28 12:16  erkan kolemen <erkankolemen@yahoo.com>
  0 siblings, 1 reply; 3+ messages in thread

From: erkan kolemen @ 2006-09-28 12:16 UTC (permalink / raw)
  To: pgsql-interfaces

Hi, 

Following code fails at PQExec. I am using PQerrorMessage() function to print error message but no output. Error code is 2. What could be the problem with select query? I tried with "drop table" it worked.

[root@hq src]# ./1
PQExec failed(2):

1.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/time.h>
#include <libpq-fe.h>

int main()
{
        char *conninfo;
        PGconn     *conn;
        PGresult   *res;

        /* Prepare connection info */
        conninfo = (char *) malloc(64);
        if (conninfo == NULL) {
                fprintf(stderr, "malloc error: %s\n", strerror(errno));
                return -1;
        }

        memset(conninfo, 0, 64);
        strncpy(conninfo, "dbname=llist user=yyy password=xxx", 63);

        /* 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 failed: %s", PQerrorMessage(conn));
                return -1;
        }

        res = PQexec(conn, "select * from lists;");
        if (PQresultStatus(res) != PGRES_COMMAND_OK)
        {
                fprintf(stderr, "PQExec failed(%d): %s\n", PQresultStatus(res), PQerrorMessage(conn));
                PQclear(res);
                return -1;
        }

        PQclear(res);

        PQfinish(conn);

        return 0;
}


 		
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^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: PGExec returns error without any comment
@ 2006-09-28 13:37  Michael Fuhr <mike@fuhr.org>
  parent: erkan kolemen <erkankolemen@yahoo.com>
  0 siblings, 0 replies; 3+ messages in thread

From: Michael Fuhr @ 2006-09-28 13:37 UTC (permalink / raw)
  To: erkan kolemen <erkankolemen@yahoo.com>; +Cc: pgsql-interfaces

On Thu, Sep 28, 2006 at 05:16:10AM -0700, erkan kolemen wrote:
>         res = PQexec(conn, "select * from lists;");
>         if (PQresultStatus(res) != PGRES_COMMAND_OK)

You're checking for the wrong result status.  Here are some excerpts
from the libpq documentation:

PGRES_COMMAND_OK
    Successful completion of a command returning no data.

PGRES_TUPLES_OK
    Successful completion of a command returning data (such as a SELECT
     or SHOW).

  Note that a SELECT command that happens to retrieve zero rows still
  shows PGRES_TUPLES_OK.  PGRES_COMMAND_OK is for commands that can
  never return rows (INSERT, UPDATE, etc.).

-- 
Michael Fuhr



^ permalink  raw  reply  [nested|flat] 3+ messages in thread

* Re: PGExec returns error without any comment
@ 2006-09-28 18:33  erkan kolemen <erkankolemen@yahoo.com>
  0 siblings, 0 replies; 3+ messages in thread

From: erkan kolemen @ 2006-09-28 18:33 UTC (permalink / raw)
  To: pgsql-interfaces

Thanks,

That was the problem!

Volkan YAZICI <yazicivo@ttnet.net.tr> wrote: On Sep 28 05:16, erkan kolemen wrote:
>         char *conninfo;
>         PGconn     *conn;
>         PGresult   *res;
> 
>         /* Prepare connection info */
>         conninfo = (char *) malloc(64);
>         if (conninfo == NULL) {
>                 fprintf(stderr, "malloc error: %s\n", strerror(errno));
>                 return -1;
>         }
> 
>         memset(conninfo, 0, 64);
>         strncpy(conninfo, "dbname=llist user=yyy password=xxx", 63);

I'd prefer a

  char conninfo[] = "dbname=llist user=yyy password=xxx";

instead of above mess.

>         /* 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 failed: %s", PQerrorMessage(conn));
>                 return -1;
>         }
> 
>         res = PQexec(conn, "select * from lists;");
>         if (PQresultStatus(res) != PGRES_COMMAND_OK)

You should be checking for PGRES_TUPLES_OK, not COMMAND_OK.

AFAIU from your name, you're from Turkey. Have you ever heard about
"PostgreSQL ile Programlama" book? You can get it freely from here:
http://www.students.itu.edu.tr/~yazicivo/doc/postgresql-ile-programlama.html


Regards.


 		
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^ permalink  raw  reply  [nested|flat] 3+ messages in thread

end of thread, other threads:[~2006-09-28 18:33 UTC | newest]

Thread overview: 3+ messages (download: mbox mbox.gz follow: Atom feed)
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2006-09-28 12:16 PGExec returns error without any comment erkan kolemen <erkankolemen@yahoo.com>
2006-09-28 13:37 ` Michael Fuhr <mike@fuhr.org>
2006-09-28 18:33 Re: PGExec returns error without any comment erkan kolemen <erkankolemen@yahoo.com>

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