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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