Postgres slowdown on large tables

I've been testing how fast I am able to insert entries in a simple
table, and I am shocked how slow postgres gets when the table gets
large.

My test program takes one day of syslog messages (~400k) and inserts
them into a sql table.  The table is created if missing.  My benchmark
program does two 'select count(*) from syslog_test;' with 10 seconds
apart and calculates how many inserts was done in that period.  It
then waits 4 minutes and repeats.

The insert peaks at 43/s with around 20k entries in the tables and
then quickly moves down to 15/s (100k) and 6/s (200k).  Here are the
test script, the benchmark script and some numbers.

  7697 ->   8072 11s 34 entry/s
 17227 ->  17701 11s 43 entry/s
 50427 ->  50824 14s 28 entry/s
 98831 ->  99033 14s 14 entry/s
151528 -> 151645 12s  9 entry/s
200084 -> 200165 12s  6 entry/s
251277 -> 251341 12s  5 entry/s

BTW:  I know this is a crude benchmark, but I really wants to insert
 syslog data in less then a day.  On the last machine I tested this (a
 little slower then the current one), I was able to insert one days
 syslog in 24 hours and 52 minues.  A little to slow. :-)
========================================================================
#!/store/bin/perl5 -w
#
# Author: Petter Reinholdtsen <pere@td.org.uit.no>
# Date:   1998-11-17
#
# Import syslog messages into SQL.  Create table syslog if missing.
#
# Usage:
#  import-syslog.pl [-l level] [-f facility]

use DBI;
use strict;
use Getopt::Std;
use vars qw($dbh $rc $level $facility $filename $opt_f $opt_l);

my %global = (table  => "syslog_test",
          dbhost => 'localhost',
          dbname => 'pere');

my @levels = qw(emerg alert crit err warning notice info debug);
my @facilities =
    qw(kern user mail daemon auth syslog lpr news uucp cron local.*);

getopts("l:f:");

$dbh = DBI->connect("dbi:Pg:dbname=$global{dbname} host=$global{dbhost}");

init_table() unless ( table_exists() );
my ($lastfilename, $local_level, $local_facility);
while (<>) {
    $filename = $ARGV;
    if ($filename ne $lastfilename) {
    print "New file $filename\n";
    $lastfilename = $filename;

    undef $opt_l if ($local_level);
    undef $opt_f if ($local_facility);
    undef $local_level;
    undef $local_facility;

    # Try to extract level or facility from filename
    for $level (@levels) {
        my @f = split(/\//, $filename);
        my $lev;
        if (($lev) = grep /^$level$/, @f) {
        $opt_l = $lev;
        print "Level=$opt_l\n";
        $local_level=1;
        }
    }
    for $facility (@facilities) {
        my @f = split(/\//, $filename);
        my $fac;
        if (($fac) = grep /^$facility$/, @f) {
        $opt_f = $fac;
        print "Facility=$opt_f\n";
        $local_facility=1;
        }
    }
    }

    chomp;
    next if (/last message repeated/);
    my $hashref = parse_old_format($_);

    $hashref->{facility} = $opt_f if ($opt_f);
    $hashref->{level} = $opt_l if ($opt_l);

    sql_syslog_insert($hashref);# if ($hashref);
}


#$rv  = $dbh->do("SELECT * from test");

$rc  = $dbh->disconnect;
print "Error disconnectiong\n" unless ($rc);

sub syslog_to_sql_date {
    my $date = shift;
    my ($year) = (localtime)[5]+1900;

    $date .=" $year";

    return $date;
}

sub parse_old_format ($) {
    my $line = shift;
    my ($date, $host, $prog, $pid, $info);

    ($date, $host) =
    $line =~ m/^(\w+ \d+ \d+:\d+:\d+) ([\.\w-]+) /;
    if ($date) { # Remove date and host info
    $line =~ s/^\w+ \d+ \d+:\d+:\d+ [\.\w-]+ //;
    }
    ($prog) =
    $line =~ m/^(\S+)[\d\[\]]*: .+$/;

    if ($prog) {
    ($pid) =
        $prog =~ m/\[(\d+)\]/;
    $prog =~ s/\[\d+\]//;
    }

    ($info) =
    $line =~ m/: (.+)$/;

    $date = syslog_to_sql_date($date);

    if ( ! $host ) {
    print "E: $line\n\n";
    return;
    }

    return {when => $date,
        host => $host,
        prog => $prog,
        pid => $pid,
        info => $info
        };
}

sub sql_syslog_insert {
    my $hashref = shift;
    my $sql = "INSERT INTO $global{table} (";
    my $values = "";
    my ($key, @keys, @values);
    for $key (keys %$hashref) {
    if ( $hashref->{$key} ) {
        push(@keys, $key);
        push(@values, sql_escape($hashref->{$key}));
    }
    }

    $sql .= join(",", @keys);
    $sql .= ") VALUES ('";
    $sql .= join("','", @values);
    $sql .= "')";

    my $rv  = $dbh->do($sql);
    print "ES: $sql\n\n" if (!$rv);
}

sub sql_escape {
  my($str) = shift;
  return undef if ( !defined $str);
  $str =~ s/\\/\\\\/;
  $str =~ s/\'/\'\'/g;
  return $str;
}

sub table_exists {
    if ( $dbh->do("SELECT * FROM $global{table}") ) {
    return 1; # TRUE
    } else {
    return ""; # FALSE
    }
}
sub init_table {
# -priority (emerg/alert/crit/err/warning/notice/info/debug)
# -facility (kern/user/mail/daemon/auth/syslog/lpr/news/uucp/cron/local*)
# dato
# hostname
# prog
# pid
# info
    my $sql =
    "CREATE TABLE $global{table} (".
    "when     datetime NOT NULL,".
    "host     varchar(40) NOT NULL,".
    "level    varchar(20),".
    "facility varchar(20),".
    "prog     varchar(20),".
    "pid      int,".
    "info     varchar(1024) NOT NULL".
    ")";
    print "Init table:\n";
    $dbh->do($sql);

}
========================================================================
#!/bin/sh
# Author: Petter Reinholdtsen <pere@td.org.uit.no>
#
# Benchmark insert rate

while true ; do
        date
        starttime=`date +%s`
        startcount=`psql -c 'select count(*) from syslog_test;'|grep '^[0-9 ]'|grep -v count`
        sleep 10
        endtime=`date +%s`
        endcount=`psql -c 'select count(*) from syslog_test;'|grep '^[0-9 ]'|grep -v count`
        time=`echo $endtime - $starttime | bc `
        rate=`echo "($endcount - $startcount)/$time"|bc`
        echo "$startcount -> $endcount $time s  $rate entry/s"
        sleep 240
done
========================================================================
--
##>  Petter Reinholdtsen <##    | pere@td.org.uit.no
 O-  <SCRIPT Language="Javascript">window.close()</SCRIPT>
http://www.hungry.com/~pere/    | Go Mozilla, go! Go!