distance vector databases and country maps

Hi,

I believe postgresql has polygon, box, circle etc datatypes which could be
useful in your situation. Depending on how you are doing your maps the
world being approximately spheroid may or may not be a consideration in how
you approach things (to avoid 2-D wraparound issues for instance).

Datatypes
http://www.postgresql.org/idocs/index.php?datatype-geometric.html#AEN3665

Operators/functions to use with those data types.
http://www.postgresql.org/idocs/index.php?functions-geometry.html

e.g.
Operator: @
Meaning: Contained or on
Usage: point '(1,1)' @ circle '((0,0),2)'

Indexes
http://www.postgresql.org/idocs/index.php?indices-types.html

CREATE INDEX name ON table USING RTREE (column);

I haven't any experience in using these features but I figure they might be
helpful to you.

Cheerio,
Link.

p.s. Yeah Postgresql is also copyrighted, but it's BSDtype :).

At 05:33 PM 10/6/01 +0200, you wrote:

Frank,
In terms of storing GIS (geographic informations systems) data in
PostgreSQL, check out PostGIS: http://postgis.refractions.net . It is a
LGPL extension to PostgreSQL to provide full spatial database
functionality for pgsql. The built-in types are just not up to full GIS
work.

As for your particular problem, yes, acquiring GIS data, particularly
detailed GIS data, can be expensive. It depends a great deal on the
country you are working in. Data here in Canada is terribly expensive;
in the USA it is much more reasonable (even free for some data sets). I
am sure there are government agencies in Germany which have very
detailed GIS data for your country, but I have no idea which ones :) I
have found the the GIS portal site http://www.geocomm.com is a good
starting point when looking for free data. Free data tends to be more
coarse than the alternatives but then at least it is free :)

Happy mapping,
Paul

Hi,

Is it possible to have multiple postgresql installations on one machine
running on the same port but on different IP addresses?

I've specified different IPs/hostnames for the virtual_host but the unix
socket clashes when I try.

Should I just move the unix sockets somewhere else with -k, what would the
impact be? I can't seem to tell psql where to find the moved unix socket.

Cheerio,
Link.

I may be wrong, but I don't think it's possible to have them on the same
port. The problem is that the TCP/IP port defaults to the same as the UNIX
sockets port, and UNIX sockets are local to the machine, so they are
completely independent of IP addresses and can not be duplicated. It is
possible to run two installs on different ports though, which is what I do
at work. Postgres 6.x on port 5432, and 7.x on port 4321. You could
probably use your OS's NAT layer to redirect anything that comes in on port
5432 of the second IP to port 4321 (look at the rewrite rules of the INPUT
chain with iptables under Linux) if you don't want to add the "port=xxx" to
the connect string of your applications though.

At 07:04 AM 10/11/01, Lincoln Yeoh wrote:

Charles Tassell <ctassell@isn.net> writes:

I may be wrong, but I don't think it's possible to have them on the same
port. The problem is that the TCP/IP port defaults to the same as the UNIX
sockets port, and UNIX sockets are local to the machine, so they are
completely independent of IP addresses and can not be duplicated.

Unix sockets need to have unique pathnames in the local filesystem.
The PG "port number" is actually only a component of the file name.
So all you need to do if you need to have conflicting port numbers
is to vary the unix_socket_directory parameter for each postmaster.

However, varying the port number is probably a simpler attack...

I can't seem to tell psql where to find the moved unix socket.

Use -h /path/to/directory/containing/socket. AFAIR you can set the
path in PGHOST environment variable, if that helps.

regards, tom lane

Thanks. I didn't know psql -h did that, thought it was for hostnames only :).

So I resorted to TCP access for the rest of the installations and moved the
sockets out of the way. However the Redhat style initscript tends to
shutdown all installations - even though I specified a different PID file
:(. I guess I might need to fix that one - coz the idea is to have them
independent.

Was actually wondering if I could change the name of the socket to
something like ...portnumber.virtual_host_name_or_ip_address

That way psql -h vhost1 would try usualprefix.defaultport.vhost1

psql by itself would try usualprefix.defaultport

(have to convert dots and slashes in addresses to underscores or something
more innocuous, or quote carefully)

Probably not that useful now that I know more about -h :).

Cheerio,
Link.

At 12:03 AM 10/13/01 -0400, Tom Lane wrote:

Charles Tassell <ctassell@isn.net> writes:

I may be wrong, but I don't think it's possible to have them on the same
port. The problem is that the TCP/IP port defaults to the same as the

UNIX