From: Tom Lane <tgl@sss.pgh.pa.us>
To: Steve Woodcock <steve.woodcock@gmail.com>
Cc: Scott Sipe <cscotts@mindspring.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Super-smack?
Date: Mon, 01 May 2006 11:15:19 -0400
Message-ID: <5882.1146496519@sss.pgh.pa.us> (raw)
In-Reply-To: <ff68c4ad0605010606k1f8147d8ue6b650b05958d562@mail.gmail.com>
References: <92F10BE1-B193-4EEA-877A-9260B55C2844@mindspring.com>
<ff68c4ad0605010606k1f8147d8ue6b650b05958d562@mail.gmail.com>
"Steve Woodcock" <steve.woodcock@gmail.com> writes:
> On 01/05/06, Scott Sipe <cscotts@mindspring.com> wrote:
>> So, my question is, before I do any further digging, is super-smack
>> flawed?
> Hmm, selects and updates of a 90k row table using the primary key, but
> no sign of a VACUUM ANALYZE...
Reasonably recent versions of PG should be able to do "the right thing"
in the presence of a simple primary key, even without any prior ANALYZE;
the planner will see the unique index and make the right conclusions
about statistics.
If the test is doing a huge number of UPDATEs and no VACUUM anywhere,
then accumulation of dead rows would eventually hurt, but it's not clear
from Scott's report if that's the issue.
I'm inclined to think there's some more subtle bias in the testbed.
I haven't dug into the code to look at how they are managing multiple
connections, but I wonder if say there's something causing the client to
not notice responses from the server right away when it's going through
libpq.
FWIW, my own experiments with tests like this suggest that PG is at
worst about 2x slower than mysql for trivial queries. If you'd reported
a result in that ballpark I'd have accepted it as probably real. 6x I
don't believe though ...
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, steve.woodcock@gmail.com, cscotts@mindspring.com
Subject: Re: Super-smack?
In-Reply-To: <5882.1146496519@sss.pgh.pa.us>
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