Thread: 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