Re: Upgrading from PostgreSQL 7.4.3

peter@vfemail.net writes:
> I'm running PostgreSQL version 7.4.3 on a Dell PowerEdge SC400 running FreeBSD 4.10.  Fresh SCSI drives were
installedin the server a week ago.  A variety of Perl, PHP, shell and perhaps other scripts read read from the
database,write records to the database, and otherwise shuffle data here, there and everywhere all day, every weekday.
Rebuildingthe server from ground zero isn't a viable option.  I'm clueless what is dependent on anything else.  Because
thesystem was built by a number of people over a period of many years, there is no one person who understands the
systemin its entirety . . . other than when something doesn't work it's a headache.   

> Where do I begin the upgrade process?

Well, the first, urgent priority for you is to update in place from
7.4.3 to 7.4.something-recent.  You are missing nearly six years worth
of bug fixes, some of them quite critical.  After that you will want to
consider updating to a more modern release series, preferably 8.4.x.
That will require a dump-and-reload, which might be painful depending
on how large your database is.  However the larger pain will be
application compatibility testing --- you'll need to test all those
various scripts to see if there are changes needed to work with the
newer PG version.

There have been some security fixes in the 7.4.x series that changed
application-visible behavior (because there was no other way to plug
the security hole).  So there is a small chance that you'd need script
fixes even for an update within 7.4.x --- you'll want to look at the
release notes to try to gauge whether you'll be affected.  I'd say it's
a lead-pipe cinch that you'll need to fix some things to move up to
8.4, though...

The release notes are here:
http://developer.postgresql.org/pgdocs/postgres/release.html
and you should definitely study the relevant pages for whichever
update you intend to undertake.

            regards, tom lane