Bug #579: Auto-VACUUM doesnt work

Paul Mamin (magamos@mail.ru) reports a bug with a severity of 4
The lower the number the more severe it is.

Short Description
Auto-VACUUM doesnt work

Long Description
I have PIII 800MHz, 128MB, HDD IDE Quantum Fibeball AS Plus 20 Gb, Slackware Linux 8.0, kernel 2.4.17, PostgreSQL
7.2b3,standard settings with fsync enabled. 

I run my example twice:
1) with
#        $conn->exec("VACUUM test");
line commented;
2) with the same line uncommented.

Results from 1):
10     1 wallclock secs ( 0.04 usr +  0.01 sys =  0.05 CPU)
20     1 wallclock secs ( 0.09 usr +  0.05 sys =  0.14 CPU)
30     1 wallclock secs ( 0.11 usr +  0.03 sys =  0.14 CPU)
40     1 wallclock secs ( 0.09 usr +  0.00 sys =  0.09 CPU)
50     1 wallclock secs ( 0.13 usr +  0.02 sys =  0.15 CPU)
60     1 wallclock secs ( 0.06 usr +  0.04 sys =  0.10 CPU)
70     1 wallclock secs ( 0.12 usr +  0.06 sys =  0.18 CPU)
80     1 wallclock secs ( 0.05 usr +  0.05 sys =  0.10 CPU)
90     2 wallclock secs ( 0.08 usr +  0.03 sys =  0.11 CPU)
100     1 wallclock secs ( 0.06 usr +  0.01 sys =  0.07 CPU)
110     3 wallclock secs ( 0.07 usr +  0.09 sys =  0.16 CPU)
120     8 wallclock secs ( 0.16 usr +  0.05 sys =  0.21 CPU)
130    12 wallclock secs ( 0.15 usr +  0.03 sys =  0.18 CPU)
140    12 wallclock secs ( 0.20 usr +  0.05 sys =  0.25 CPU)
150    14 wallclock secs ( 0.22 usr +  0.09 sys =  0.31 CPU)
160    14 wallclock secs ( 0.27 usr +  0.03 sys =  0.30 CPU)
170    15 wallclock secs ( 0.13 usr +  0.03 sys =  0.16 CPU)
180    16 wallclock secs ( 0.19 usr +  0.07 sys =  0.26 CPU)
190    17 wallclock secs ( 0.17 usr +  0.08 sys =  0.25 CPU)
200    17 wallclock secs ( 0.20 usr +  0.02 sys =  0.22 CPU)
210    19 wallclock secs ( 0.17 usr +  0.08 sys =  0.25 CPU)
220    19 wallclock secs ( 0.22 usr +  0.04 sys =  0.26 CPU)
230    20 wallclock secs ( 0.16 usr +  0.03 sys =  0.19 CPU)
240    21 wallclock secs ( 0.18 usr +  0.05 sys =  0.23 CPU)
250    21 wallclock secs ( 0.20 usr +  0.06 sys =  0.26 CPU)
260    23 wallclock secs ( 0.17 usr +  0.07 sys =  0.24 CPU)
270    23 wallclock secs ( 0.19 usr +  0.01 sys =  0.20 CPU)
280    24 wallclock secs ( 0.18 usr +  0.08 sys =  0.26 CPU)
290    25 wallclock secs ( 0.21 usr +  0.05 sys =  0.26 CPU)
300    26 wallclock secs ( 0.21 usr +  0.08 sys =  0.29 CPU)
...

And results from 2):
10     0 wallclock secs ( 0.06 usr +  0.02 sys =  0.08 CPU)
20     1 wallclock secs ( 0.08 usr +  0.04 sys =  0.12 CPU)
...
1000     1 wallclock secs ( 0.10 usr +  0.01 sys =  0.11 CPU)

It seems that auto-VACUUM doesnt work properly... :(

Sample Code
#!/usr/bin/perl

use Pg;
use Benchmark;

$conn = Pg::connectdb("dbname=test");
die $conn->errorMessage unless PGRES_CONNECTION_OK eq $conn->status;

$conn->exec("BEGIN");
$result = $conn->exec("CREATE TABLE test (a int primary key, b int)");
for ($i = 0; $i < 100; $i++) {
    $conn->exec("INSERT INTO test VALUES ($i, $i)");
}
$conn->exec("COMMIT");

$conn->exec("BEGIN");
$t0 = new Benchmark;
for ($i = 0; $i < 300; $i++) {
    for ($j = 0; $j < 100; $j++) {
        $conn->exec("UPDATE test SET b=b+1 WHERE a=$j");
    }
    if ($i % 10 == 9) {
    $conn->exec("COMMIT");
#        $conn->exec("VACUUM test");
    $conn->exec("BEGIN");
    $t1 = new Benchmark;
    print $i+1 ."\t" . timestr(timediff($t1, $t0)) . "\n";
    $t0 = $t1;
    }
}
$conn->exec("COMMIT");


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