Your confirmation is correct with one slight technical exception: specifying the port doesn't technically cause the system to know which version of postgres to use.
In my previous post, I forgot to mention a related note: the version of pg_dump that you're using matters slightly. pg_dump can typically be used with older postgres installations, but not newer ones. So you should prefer using the 8.1.4 version of pg_dump to dump at least your 8.1.4 postmaster, but probably also your 7.3.4 postmaster.
A 7.3.4 pg_dump client will probably not be able to run against an 8.1.4 postmaster.
Otherwise, pg_dump doesn't really care about the version as much as it cares about being able to connect to a postmaster. That's what specifying the port helps it do. When you don't specify the port, it just tries port 5432. If it finds a postmaster listening there, great, it will try to dump it; otherwise, it will fail with a complaint that it couldn't connect to anything on 5432.
--
Thomas F. O'Connell
Sitening, LLC
3004B Poston Avenue
Nashville, TN 37203-1314
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"Thomas F. O'Connell" <tfo@sitening.com> wrote on 08/02/2006 02:04:35 PM:
> You'll need to specify the non-default port explicitly in your
> pg_dump command in order to back up the postmaster running on 55432.
>
> E.g., pg_dump -p 55432 -U postgres -C -D -f /tmp/$(date+%F)owl.sql owl
>
> By default, the postgres command-line utilities attempt to connect
> to 5432 (or $PGPORT or whatever is configured as the default port).
>
> In the meantime, you're still backing up the 7.3.4 postmaster with
> that script.
>
> --
> Thomas F. O'Connell
> Sitening, LLC
To confirm: what you're saying it that by specifying the port in my command the system knows which database to backup and which version of Postgresql to use.
Thank you for the assistance.
Margaret Gillon