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Re: BUG #4919: CREATE USER command slows down systemperformance

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Lauris Ulmanis <lauris(dot)ulmanis(at)mykoob(dot)com>
Cc: "'Heikki Linnakangas'" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-bugs(at)postgresql(dot)org, pgsql-performance(at)postgresql(dot)org
Subject: Re: BUG #4919: CREATE USER command slows down systemperformance
Date: 2009-07-15 14:02:09
Message-ID: 20090715140209.GF4551@alvh.no-ip.org (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-performance
Lauris Ulmanis wrote:
> Hello again!
> 
> I did test on my local test server
> 
> I created up 500 000 users in function loop very quickly - within 48
> seconds. I did again this script reaching up to 1 billion users - results
> was the same - 48 seconds. It is very quickly.
> 
> But problem seems is with transaction preparation because if in database is
> 1 billion users and I want to create 1 new - it will take 4 seconds! 
> 
> After that I generated up to 2 billion users in this server (generation
> process took just 1.44 minutes of times - again quickly).
> 
> And did 1 user creation again - now it took 9 seconds of time!
> 
> What is a reason of this slowness? Is there a workaround or solution how to
> avoid it? 

My bet is on the pg_auth flat file.  I doubt we have ever tested the
behavior of that code with 1 billion users ...

Do you really need 1 billion users?  Are you planning on giving accounts
to every human being in the planet or what?  I mean, what's the point of
this test?

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

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