[postgis-devel] New uninstall_postgis.sql script

[Mark Cave-Ayland]

Tom Lane wrote:

> CREATE OR REPLACE what?  It seems unlikely that you need to change the
> names of the I/O functions, and you can't change the type's
> representational properties if you're hoping to do upgrade-in-place.
> So I'm not really seeing what CREATE OR REPLACE TYPE would buy exactly.
> 
> Replacing the .so doesn't seem to be a problem, so long as you avoided
> putting any version numbers into the .so name referenced in the SQL
> function definitions.

Well we don't use the old PostgreSQL mechanism where the library 
contains the major/minor numbers with a symlink; however with 1.4 the 
resulting library file is named "postgis-1.4.so" or similar. The reason 
for this is that 1.4 is sufficiently different under the hood for it to 
be extremely useful to have different versions of PostGIS installed in 
different databases within the same cluster for testing.

I think there are two cases here: the first is the 8.3 -> 8.4 migration 
using the same 1.3 version of PostGIS which won't be a problem. The 
second case is trying to upgrade from 8.3 with PostGIS 1.3 to 8.4 with 
PostGIS 1.4 at the same time which is the one most likely to break, 
especially as we have seen in the wild that due to neglect within the 
upgrade script, many upgrades have not been 100% successful in the past. 
But we need to treat these as two distinct cases.


ATB,

Mark.

-- 
Mark Cave-Ayland - Senior Technical Architect
PostgreSQL - PostGIS
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