Re: 7.4 JDBC driver with 8.1 server?

On Fri, 17 Feb 2006, Tom Lane wrote:

> Can anyone comment offhand on how well a 7.4-vintage JDBC driver
> (build 215 to be exact) would interoperate with a PG 8.1 server?
> I need to make some recommendations about RHEL update procedures
> and this question came up.
>
> I have some recollection that JDBC looks into the system catalogs
> to an extent that makes old drivers likely to break with newer
> servers, but don't really know the details.
>

That depends what you are doing with the driver.  I happen to have a 7.4 
driver running against an 8.1 server without any problems, but all it does 
is issue queries, it doesn't do anything more complicated.  Anyone making 
use of DatabaseMetaData[1] will certainly have problems because these 
methods provide a standard way of getting system information and have not 
been updated past the 7.4 release.  A quick run of the 7.4 regression test 
against a 8.1 server shows that anything retrieving foreign key 
information will not work.  If this really is the only thing wrong it 
would be a pretty simple fix to backport.  It's not been our policy to 
ensure forward compatibility and the 7.4 driver isn't really maintained 
anymore, but a I'd ignore that for a simple change for a big pg 
contributor.

If this is just a step during an upgrade it seems reasonable to do, but 
your message sounds a little bit like your thinking of keeping it that way 
for a while.  Certainly the 8.0 introduction of strong typing has caused a 
lot of people problems, but people are certainly not going to be happy if 
they've upgraded, but don't get to use things like Savepoints.  I also 
might consider using an 8.2dev driver that has been adjusted to set the 
stringtype[2] parameter to unspecified.  This would reduce the impact of 
the 8.0 changes while still providing new features.

Kris Jurka

[1] http://java.sun.com/j2se/1.5.0/docs/api/java/sql/DatabaseMetaData.html
[2] http://jdbc.postgresql.org/documentation/head/connect.html#connection-parameters