async queries in Perl and poll()/select() loop - how to make them work together?

Hello,

I'm using CentOS 5.5 Linux with stock perl v5.8.8
and have installed DBD-Pg-2.17.1 via CPAN shell
and I'm using postgresql-server-8.4.5-1PGDG.rhel5.

I've prepared a simple test case demonstrating
my problem - it is listed at the bottom. It works ok,
when I remove {pg_async => PG_ASYNC}.

I have a small multiplayer game, a non-forking daemon
reading/writing to sockets and running in a IO::Poll loop.

I'd like to add player statistics to it, so I was hoping
that I could call the simple INSERT/UPDATE
statements asynchronously from the loop and
I don't need to fetch any results of those queries,
because displaying statistics will be done by
web scripts, not by my game daemon.

I.e. I would like to "fire and forget" queries.

But unfortunately I get the error:
DBD::Pg::st execute failed: Cannot execute
until previous async query has finished
even though I'm not using PG_OLDQUERY_WAIT

Does anybody know what is wrong and
how would you use async queries with
poll()/select() loops anyway?

I can't even call "$dbh->pg_result if $sth->pg_ready",
on every loop iteration, because I can have
several queries running at that moment,
I don't want to iterate through a list of my $sth's...
This defeats my target of quick poll()-looping.

Regards
Alex

P.S. Here is my test case and it is also listed at
http://stackoverflow.com/questions/4065758/async-queries-with-dbdpg-fail-with-cannot-execute-until-previous-async-query-h

#!/usr/bin/perl -w

use strict;
use DBI;
use DBD::Pg qw(:async);

use constant DBNAME => 'snake';
use constant DBUSER => 'snake';
use constant DBPASS => 'snake';

use constant SQL_CREATE_TABLES => q{
/*
create table pref_users (
id varchar(32) primary key,
first_name varchar(32),
last_name varchar(32),
female boolean,
avatar varchar(128),
city varchar(32),
lat real check (-90 <= lat and lat <= 90),
lng real check (-90 <= lng and lng <= 90),
last_login timestamp default current_timestamp,
last_ip inet,
medals smallint check (medals > 0)
);

create table pref_rate (
obj varchar(32) references pref_users(id),
subj varchar(32) references pref_users(id),
good boolean,
fair boolean,
nice boolean,
about varchar(256),
last_rated timestamp default current_timestamp
);

create table pref_money (
id varchar(32) references pref_users,
yw char(7) default to_char(current_timestamp, 'YYYY-WW'),
money real
);
create index pref_money_yw_index on pref_money(yw);

create table pref_pass (
id varchar(32) references pref_users
);

create table pref_misere (
id varchar(32) references pref_users
);
*/

create or replace function pref_update_users(_id varchar,
_first_name varchar, _last_name varchar, _female boolean,
_avatar varchar, _city varchar, _last_ip inet) returns
void as $BODY$
begin

update pref_users set
first_name = _first_name,
last_name = _last_name,
female = _female,
avatar = _avatar,
city = _city,
last_ip = _last_ip
where id = _id;

if not found then
insert into pref_users(id, first_name,
last_name, female, avatar, city, last_ip)
values (_id, _first_name, _last_name,
_female, _avatar, _city, _last_ip);
end if;
end;
$BODY$ language plpgsql;
};

eval {
my $dbh = DBI->connect_cached('dbi:Pg:dbname=' .
DBNAME, DBUSER, DBPASS, {
AutoCommit => 1,
PrintWarn => 1,
PrintError => 1,
RaiseError => 1,
FetchHashKeyName => 'NAME_lc',
pg_enable_utf8 => 1
}, {pg_async => PG_ASYNC});

$dbh->do(SQL_CREATE_TABLES, {pg_async => PG_ASYNC});
};
warn $@ if $@;

for my $i (1..10) {
eval {
my $dbh = DBI->connect_cached('dbi:Pg:dbname=' .
DBNAME, DBUSER, DBPASS, {
AutoCommit => 1,
PrintWarn => 1,
PrintError => 1,
RaiseError => 1,
FetchHashKeyName => 'NAME_lc',
pg_enable_utf8 => 1
}, {pg_async => PG_ASYNC});

#$dbh->pg_result;

my $sth = $dbh->prepare_cached(
q{select pref_update_users(?, ?, ?, ?, ?, ?,
NULL)}, {pg_async => PG_ASYNC});

$sth->execute('ID123', 'Alexander', 'Farber', undef,
undef, undef);
};
warn $@ if $@;
}