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Re: Benchmark comparing PostgreSQL, MySQL and Oracle

From: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
To: Sergio Lopez <sergio(dot)lopez(at)nologin(dot)es>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Benchmark comparing PostgreSQL, MySQL and Oracle
Date: 2009-02-20 19:48:06
Message-ID: 36e682920902201148p50a4785fj140053ef41fbb254@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, Feb 20, 2009 at 1:15 PM, Sergio Lopez <sergio(dot)lopez(at)nologin(dot)es>wrote:

> On the other hand, I've neved said that what I've done is the
> Perfect-Marvelous-Definitive Benchmark, it's just a personal project,
> and I don't have an infinite amount of time to invest on it.


When you make comments such as "As for databases, both Oracle and MySQL show
nice numbers, but it's PostgreSQL who stands in the top, giving consistent
results with each environment and workload", you should make sure that your
test is correct.  Otherwise you're making statements without any real
basis-in-fact.

Having this said, the benchmark is not as unfair as you thought. I've
> taken care to prepare all databases to meet similar values for their
> cache, buffers and I/O configuration (to what's possible given their
> differences), and the I've left the rest as comes by default (for
> Oracle I've used the OLTP template).


Oracle's buffer cache is different than Postgres'.  And there are several
other tuning paramaters which control how the buffer cache and I/O between
cache and disk is performed.  Making them the same size means nothing.  And,
as I said, you still didn't mention other important tuning parameters in
MySQL, Postgres, or Oracle.  So either you don't know about them, or you
didn't bother to tune them, which is odd if you were trying to run a truly
comparative benchmark.


> Yes, BenchmarkSQL is NOT the perfect tool for database benchmarking and
> it is NOT a valid TPC-C test (I've made this clear in the article), but
> I've looked at its source (you assume I blindly used it, but actually
> I've even made some changes to make it work with Ingres for other
> purposes) and I find it fair enough due to the simplicity of the
> queries it executes. I found no other evident optimization than the
> "vacuum analyze" in the LoadData application.


Did you fix the bug in, I believe, the Order Status transaction that can
cause an endless loop?  I would call giving the Postgres optimizer correct
statistics and leaving Oracle and MySQL with defaults an optimization.


> Obviously, you can optimize the queries to perform better in Oracle,
> the same way you can do with any other DB, but doing that would be
> cheating. The key here is to keep the queries as simple as possible,
> and BenchmarkSQL does this nicely.


BenchmarkSQL is flawed.  You need to review the code more closely.

Of course, my benchmark it's somewhat peculiar by the fact (that you
> haven't mentioned) that all databases files reside in volatile storage
> (RAM) by using tmpfs, which makes something similar (but not the
> same) as using DIRECT_IO with an extremly fast storage. But, again, all
> databases are given equal consideration.


You're right, it's not the same.  Oracle can benefit by using real direct
I/O, not half-baked simulations which still cause double-buffering between
the linux page cache and the database buffer cache.


> Finally, about the license issue, (also) not trying to be rude,
> forbiding people to publish benchmark of their products is simply
> stupid (and it lacks for legal basis in most countries). The only reason
> they do this is to scare kids and be able to make up their own results.
> Of course, if you allow people to publish benchmarks there will be
> some loosely done, but also there'll be others properly made (and made
> by people non-related with any database vendor).


Your benchmark was flawed.  You made condescending statements about Oracle
and MySQL based on your bad data.  That's why they don't let you do it.

IMHO, worse than having loosely done benchmarks is having people saying
> things like "if you fix the bugs, Oracle (out of the box in OLTP
> config) will come out 60%" or "Oracle comes out twice as fast as PG on
> Linux" without any proof to support this words. At least, benchmarks
> are refutable by using logic.


Your benchmark was flawed, you didn't tune correctly, and you made
statements based on bad data; refute that logic :)

-- 
Jonah H. Harris, Senior DBA
myYearbook.com

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Subject: Re: Benchmark comparing PostgreSQL, MySQL and Oracle
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