Re: Performance comparison between Postgres and Greenplum

On Wed, Jul 15, 2009 at 9:18 AM, Alex Goncharov
<alex-goncharov(at)comcast(dot)net>wrote:

> ,--- You/Suvankar (Wed, 15 Jul 2009 18:32:12 +0530) ----*
> | Yes, I have got 2 segments and a master host. So, in a way processing
> | should be faster in Greenplum.
>
> No, it should not: it all depends on your data, SQL statements and
> setup.
>
> In my own experiments, with small amounts of stored data, PostgreSQL
> beats Greenplum, which doesn't surprise me a bit.

Agreed. You're only operating on 99,000 rows. That isn't really
enough rows to exercise the architecture of shared-nothing clusters.
Now, I don't know greenplum very well, but I am familiar with another
warehousing product
with approximately the same architecture behind
it. From all the testing I've done, you need to get into the 50
million plus row range before the architecture starts to be really
effective. 99,000 rows probably fits completely into memory on the
machine that you're testing PG with, so your test really isn't fair.
On one PG box, you're just doing memory reads, and maybe some high-speed
disk access, on the Greenplum setup, you've got network overhead on top of
all that. Bottom
line: You need to do a test with a number of rows that won't fit into
memory, and won't be very quickly scanned from disk into memory. You
need a LOT of data.

--Scott