Обсуждение: Problem with Large Object Interface of pgsql_perl5

I'm using PostgreSQL 6.5.3, Perl 5.005_03, and pgsql_perl5 1.8.0 on
Linux (intel).

Running this program:

#!/usr/bin/perl
use strict;
package Main;

use Pg;

my $db_name='excised';
my $db_user='excised';
my $db_passwd='excised';

# Connect to the database server
my $dbconn = Pg::connectdb("dbname=$db_name user=$db_user
password=$db_passwd");
if($dbconn->status ne PGRES_CONNECTION_OK){
# We failed to get a connection, exit with error  my $error=$dbconn->errorMessage;  print "Error on connection:
$error\n"; exit;
 
}

print "Database connection opened\n";

my $newoid = $dbconn->lo_creat(PGRES_INV_WRITE|PGRES_INV_READ);

if($newoid == PGRES_InvalidOid){  my $error = $dbconn->errorMessage;  print "Error on lo_creat: $error\n";  exit;
}

print "LO created\n";

my $fd = $dbconn->lo_open($newoid,PGRES_INV_WRITE);

if($fd == -1){
# Error on opening new oid  my $error = $dbconn->errorMessage;  print "Error on lo_open (oid = $newoid): $error\n";  #
Tryto unlink the oid  $dbconn->lo_unlink($newoid);  exit;
 
}

print "LO opened\n";

my $content = 'This is a test of the emergency broadcasting system, in the
event of a real emergency...';

my $numbytes=$dbconn->lo_write($fd,$content,length($content));

if($numbytes != length($content)){  my $rightnum=length($content);  my $error = $dbconn->errorMessage;  print "Error on
lo_write($numbytes != $rightnum): $error\n";  # Try to unlink the oid  $dbconn->lo_close($fd);
$dbconn->lo_unlink($newoid); exit;
 
}

print "LO written\n";

$dbconn->lo_close($fd);

$dbconn->lo_unlink($newoid);


I get this output:

Database connection opened
LO created
Error on lo_open (oid = 46401): ERROR:  lo_lseek: invalid large obj
descriptor (0)

Can anyone tell me what I'm doing wrong?

All help is greatly appreciated.

Ken Causey
PremierNET, Inc.

Ken Causey <ken@premiernet.net> writes:
> Can anyone tell me what I'm doing wrong?

Not doing the lo_open inside a transaction.  You need begin ... end
around any use of an open large object.  (This has always been true,
but older versions of Postgres didn't enforce it --- they'd just die
occasionally if you broke the rule.  Now, open LO handles are auto-
closed at transaction commit, which is to say at end of statement
if you're not inside a BEGIN block.)
        regards, tom lane

Edmund Mergl was kind enough to point out my error and now
that I look back at the Programmer's documentation I see it.  Someone
might want to update the Pg man page to reflect this.  Thanks!

Ken Causey
PremierNET, Inc.

At 01:11 PM 3/31/00 -0500, Tom Lane wrote:
>Ken Causey <ken@premiernet.net> writes:
>> Can anyone tell me what I'm doing wrong?
>
>Not doing the lo_open inside a transaction.  You need begin ... end
>around any use of an open large object.  (This has always been true,
>but older versions of Postgres didn't enforce it --- they'd just die
>occasionally if you broke the rule.  Now, open LO handles are auto-
>closed at transaction commit, which is to say at end of statement
>if you're not inside a BEGIN block.)
>
>            regards, tom lane
>
>

> Edmund Mergl was kind enough to point out my error and now
> that I look back at the Programmer's documentation I see it.  Someone
> might want to update the Pg man page to reflect this.  Thanks!

What "Pg man page"? Where? Can't fix what I can't find...

                   - Thomas

--
Thomas Lockhart                lockhart@alumni.caltech.edu
South Pasadena, California

On Fri, 31 Mar 2000, Thomas Lockhart wrote:
> > Edmund Mergl was kind enough to point out my error and now
> > that I look back at the Programmer's documentation I see it.  Someone
> > might want to update the Pg man page to reflect this.  Thanks!
>
> What "Pg man page"? Where? Can't fix what I can't find...

Use perldoc Pg to read it.  It's packaged as /usr/lib/perl5/man/man3/Pg.3 in
the RPM.  It is located at src/interfaces/perl5/blib/man3/Pg.3 in the tarball.

--
Lamar Owen
WGCR Internet Radio
1 Peter 4:11

> > What "Pg man page"? Where? Can't fix what I can't find...
> Use perldoc Pg to read it.  It's packaged as /usr/lib/perl5/man/man3/Pg.3 in
> the RPM.  It is located at src/interfaces/perl5/blib/man3/Pg.3 in the tarball.

Sheesh, a whole 'nother set of docs to look at. Hopefully someone else
will pick it up...

                     - Thomas

--
Thomas Lockhart                lockhart@alumni.caltech.edu
South Pasadena, California