Re: more anti-postgresql FUD

Hello,

I'm author and maintainer of ZABBIX and the manual. I would like to add
some comments to the thread.

First of all, ZABBIX supports three database engines: MySQL, Oracle and
PostgreSQL. It uses absolutely standard SQL, same for all three
database engines. We have absolutely no intention to push or recommend
one of those. I'm big fan of PostgreSQL and having a choice I would
choose PostgreSQL for anything except ZABBIX.

Unfortunately PostgreSQL performs much slower than MySQL doing large
number of updates for one single table. By its nature ZABBIX requires
to execute hundreds of updates per second for large installations.
PostgreSQL cannot handle this nicely.

Do a simple test to see my point:

1. create table test (id int4, aaa int4, primary key (id));
2. insert into test values (0,1);
3. Execute "update test set aaa=1 where id=0;" in an endless loop

I just did the test on PostgreSQL 7.4.12 and MySQL 5.0.22 (MyISAM,
sorry had no configured InnoDB). Ubuntu 6.0.6, AMD64, 2GB, default
database settings.

MySQL performs very well, approximately 15000-20000 updates per second
with no degradation of performance.

PostgreSQL does approximately 1600 records per second for the first
10000, then 200rps for the first 100k records, and then slower and
slower downgrading to 10-20 rps(!!!) when reaching 300k.

The manual states that PostgreSQL works ten times slower for ZABBIX, in
reality it is much worser.

Yes, I'm aware of autovacuuming, etc. But it eats resources and I
cannot handle to run it periodically because I want steady performance
from my application. I do not want to see ZABBIX performing slower just
because of database housekeeper.

Several years ago I contacted PostgreSQL developers but unfortunately
the only answer was "Run vacuum. We won't change PostgreSQL to reuse
unused tuples for updates".

Perhaps something has changed in recent releases of PostgreSQL, I don't
think so. Please correct me if I'm wrong.

Kind regards,
Alexei