Async queries with DBD::Pg fail with: Cannot execute until previous async query has finished

Question

Hello,

I'm using CentOS 5.5 Linux (same as Redhat 5.5) 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 and friends.

I have prepared a simple test case demonstrating my problem - it is listed at the bottom.

My code works ok, when I remove {pg_async => PG_ASYNC}

My background is that I have a small Facebook game running as a non-forking Unix daemon with IO::Poll. I would like to add some statistics for the players, but I don't want to throttle my poll-loop, so I would like to send mostly INSERT/UPDATE commands asynchronously and I don't need any return values from the database - because for reading/displaying statistics I will have separate web-scripts.

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

Here is my code (My daemon should reconnect to PostgreSQL whenever connection is lost, that is why I use *_cached methods and do not exit on eval { .... } exceptions):

#!/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 $@;
}

Thank you, Alex