[postgis-users] OT Understanding slow queries

Paragon Corporation lr at pcorp.us
Thu Sep 1 16:45:19 PDT 2011

Honestly I have little idea.  In theory you should fair better with Linux,
but I think it depends on the kinds of processes you run how much better it
is and how much ram you have.  One advantage that Linux has over windows
(which is an advantage when running 32-bit Linux even, but more of an
advantage I think when you are running 64-bit Linux) is that you can
allocate more shared memory so processes that benefit on a lot of shared
memory should benefit (basically processes where you are using more or less
the same data in different ways can live in RAM.  Windows is limited not
just for the 32-bit but also the 64-bit and I think this is just a
fundamental flaw in PostgreSQL on windows.
So generally speaking on windows I can't boost my shared memory more than
say I think about 700 - 1GB without running into crashing issues.
As far as work mem and so forth is concerned, on 32-bit windows you can have
as much as 4GB per postgres process (and more with 64-bit windows) , but of
course if you are running 
Linux and 64-bit at that you can go up way more.
I'm sure Linux folks will shoot me for saying this and chew me out, but I
haven't really noticed much of a difference running my processes on 64-bit
Linux vs. 32-bit window,
but then again my processes are probably different from other peoples and I
don't have a 32G ram Linux to take advantage of the massive more shared
memory I can allocate.
So on the low end (say 4-8GB ram range I suspect there isn't much of a
difference, but when you get higher to the 32GB/64GB range, you would
probably do a lot better with Linux.


From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Charles
Sent: Thursday, September 01, 2011 3:10 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] OT Understanding slow queries

Hi Regina 

I am revisiting this again.  How much of a performance difference should one
expect to see between the 32 bit version and the 64 bit version of postgres
when using PostGIS for typical gis queries like filtering by bounding box,
locating nearest points etc? Depending on how I break up my data, I'll have
anywhere from 200k to 260M records per table depending on how I partition it
on a machine with 32G of ram.

I am trying to make a case to use linux for a specific project but without
being able to say there are significant gains (in performance) I'm just
fighting an uphill battle. At best right now I can use the latest
postgis/postgresql under windows but only 32 bit.


On Aug 26, 2011, at 3:50 PM, Paragon Corporation wrote:

 >  Sadly it's for immediate production use and I'm forced to use windows
which limits my version choices a bit given my lack of skill under windows
to build postgis :(

 >  charles 
You know we do have pretty much latest builds of PostGIS (even trunk on
PostGIS website for windows).
and as far as PostgreSQL -- they have released windows binaries for even
PostgreSQL 9.1 RC1
Can't get too much more current than that (all without having to compile
anything unless you are talking about the 64-bit versions).
http://www.postgis.us <http://www.postgis.us/> 

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