Subject: ECPG and NULL indicators
From: Edmund Bacon <ebacon@onesystem.com>
To: pgsql-bugs@postgresql.org
Content-Type: text/plain
Message-Id: <1066943115.5145.3.camel@elb_lx.onesystem.ca>
Mime-Version: 1.0
Date: Thu, 23 Oct 2003 15:05:15 -0600
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============================================================================
                        POSTGRESQL BUG REPORT
============================================================================


Your name		:	Edmund Bacon
Your email address	:	ebacon (at) onesystem (dot) com


System Configuration
---------------------
  Architecture       :   Intel Pentium

  Operating System   :   Linux 2.4.20

  PostgreSQL version :   PostgreSQL-7.3.3

  Compiler used      :	 gcc-3.2.2


Please enter a FULL description of your problem:
------------------------------------------------

ecpg does not correctly set null indicators when storage for the
string is dynamically allocated


Please describe a way to repeat the problem.   Please try to provide a
concise reproducible example, if at all possible: 
----------------------------------------------------------------------

CREATE TABLE strings (string text);

insert into strings values('able');
insert into strings values(null);
insert into strings values('baker');
insert into strings values(null);


Source for foo.pgc:

============================================================

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

EXEC SQL WHENEVER SQLERROR sqlprint;

EXEC SQL INCLUDE sqlca;

int main()
{
    int i;
    EXEC SQL BEGIN DECLARE SECTION;
    char **a_str;
    int *a_str_ind;

    char str[5][20];
    int  str_ind[5];
    EXEC SQL END DECLARE SECTION;


    EXEC SQL CONNECT TO test;


    printf("Test one: alloced string, allocated indicator:\n");

    a_str = NULL;
    a_str_ind = NULL;

    EXEC SQL SELECT string INTO :a_str :a_str_ind FROM strings;

    printf("indicator      string\n");
    for(i = 0; i < sqlca.sqlerrd[2]; i++)
	printf("%8d       \"%s\"\n", a_str_ind[i], a_str[i]);
    
    free(a_str);
    free(a_str_ind);


    printf("\nTest two: alloced string, unalloced indicator:\n");
    a_str = NULL;
    for(i = 0; i < 5; i++) str_ind[i] = 99;

    EXEC SQL SELECT string INTO :a_str :str_ind FROM strings;

    printf("indicator      string\n");
    for(i = 0; i < sqlca.sqlerrd[2]; i++)
	printf("%8d       \"%s\"\n", str_ind[i], a_str[i]);

    free(a_str);


    printf("\nTest three: unalloced string, alloced indicator:\n");
    a_str_ind = NULL;
    bzero(str, sizeof(str));

    EXEC SQL SELECT string INTO :str :a_str_ind FROM strings;
    printf("indicator      string\n");
    for(i = 0; i < sqlca.sqlerrd[2]; i++)
	printf("%8d       \"%s\"\n", a_str_ind[i], str[i]);

    free(a_str_ind);


    printf("\nTest four: unalloced string, unalloced indicator:\n");
    bzero(str, sizeof(str));
    for(i = 0; i < 5; i++) str_ind[i] = 99;

    EXEC SQL SELECT string INTO :str :str_ind FROM strings;
    printf("indicator      string\n");
    for(i = 0; i < sqlca.sqlerrd[2]; i++)
	printf("%8d       \"%s\"\n", str_ind[i], str[i]);


    return 0;
}

==================================================================

Output for foo:
==================================================================
Test one: alloced string, allocated indicator:
indicator      string
      -1       "able"
       0       ""
       0       "baker"
       0       ""

Test two: alloced string, unalloced indicator:
indicator      string
      -1       "able"
      99       ""
      99       "baker"
      99       ""

Test three: unalloced string, alloced indicator:
indicator      string
       0       "able"
      -1       ""
       0       "baker"
      -1       ""

Test four: unalloced string, unalloced indicator:
indicator      string
       0       "able"
      -1       ""
       0       "baker"
      -1       ""

==================================================================

Note that when the storage for the string is allocated, only the first 
element of the indicator array is set.  This value is the value of
the indicator for the last string in the string array, which can be
confirmed by using the appropriate ORDER BY clause.

This problem does not arise with allocated integer or float values.
This problem occurs if string is any multi-char type (e.g. TEXT, CHAR(),
or VARCHAR())