DBD::ODBC - Why do i get an "out of memory" exception?

karlgoethebier has asked for the wisdom of the Perl Monks concerning the following question:

Hi all,

in some older code i found something like this:


do {
     my @row;
     while (@row = $sth->fetchrow_array()) {
        # do stuff here
     }
  } while ( defined( $sth->{odbc_more_results}) );
[download]

This one throws an "out of memory" exception. I don"t know who wrote it ;-)

According to the manual of DBD::ODBC the code should be:

do {
     my @row;
     while (@row = $sth->fetchrow_array()) {
        # do stuff here
     }
  } while ( $sth->{odbc_more_results} );
[download]

This one works as expected. No need to worry - i use this code.

But i wonder why the first example fails.

Update: defined for ever?

#!/usr/bin/env perl                                                   
+                        

use feature qw (say);
use strict;
use warnings;

my $foo;

( defined $foo ) ? say qq(D'oh!) : say qq(No!);

$foo = 0;

( defined $foo ) ? say qq(D'oh!) : say qq(No!);
[download]

Thank you very much for any hint and best regards, Karl

ŤThe Crux of the Biscuit is the Apostropheť

Comment on DBD::ODBC - Why do i get an "out of memory" exception? Select or Download Code

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Re: DBD::ODBC - Why do i get an "out of memory" exception? by Laurent_R (Canon) on Apr 18, 2014 at 13:17 UTC
Yes, probably "defined for ever". It is quite possible that your method just keeps returning a false but defined value (say zero or an empty string) even when that is no more piece of data to return.	[reply]
Re^2: DBD::ODBC - Why do i get an "out of memory" exception? by karlgoethebier (Abbot) on Apr 18, 2014 at 14:22 UTC
"It is quite possible that your method just keeps returning a false but defined value..." Yes. I should study the sources... Thanks and best regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply]
Re: DBD::ODBC - Why do i get an "out of memory" exception? by mje (Curate) on Apr 22, 2014 at 17:15 UTC
odbc_more_results returns 1 when there are more results and 0 when there are no more results. As you have seen both are defined but one is false.	[reply]
Re^2: DBD::ODBC - Why do i get an "out of memory" exception? by karlgoethebier (Abbot) on Apr 22, 2014 at 17:47 UTC
"As you have seen both are defined but one is false..." Yes. Thank you mje and best regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply]
Re: DBD::ODBC - Why do i get an "out of memory" exception? by locked_user sundialsvc4 (Abbot) on Apr 18, 2014 at 12:57 UTC
On the one hand, I do believe that the use of `defined()` in the original code is incorrect. But, on the other hand, I do not see from what has been presented here a valid cause for an “out of memory” condition. I suspect that the true cause of the problem lies within the body of the loop, and, unless you can actually, at-will reproduce the condition using exactly the code snippet you posted here, you should assume the same. Never “think you know” why a piece of code is screwing-up ... prove it.
Re^2: DBD::ODBC - Why do i get an "out of memory" exception? by karlgoethebier (Abbot) on Apr 18, 2014 at 14:05 UTC
"I suspect that the true cause of the problem lies within the body of the loop..." ~~Mmh, i don't think so.~~ No. I just join each row and print to a CSV file the usual way. Regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply]