Re: ALTER EXTENSION UPGRADE, v3

Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com> writes:
> The latest extension might drop some functions.

Then the upgrade script contains the DROP commands.

> I'm still not clear what "upgrade" means. if module authors wrote
> functions with C, they can just replace .so to upgrade. If with
> SQL or PL/pgSQL, they should execute CREATE OR REPLACE FUNCTION.

When do you execute those statements? Certainly, you want the user to
issue ALTER EXTENSION foo UPGRADE and be done with it.

> The patch seems useful to upgrade from NULL to 1.0, but I cannot
> imagine how it work for cases from 1.0 to higher versions.
> For example, if we have 3 versions of a module below:
> NULL unmanaged functions only
> v1 EXTENSION support with an additional function
> v2 EXTENSION support with another function.
> How do we write upgrading scripts for NULL=>v1, NULL=>v2, and v1=>v2 ?

Well, you write 3 scripts.

Let's consider an example, the lo contrib, with its 3 objects:

CREATE DOMAIN lo AS pg_catalog.oid;
CREATE OR REPLACE FUNCTION lo_oid(lo) …
CREATE OR REPLACE FUNCTION lo_manage() …

Now, the upgrade script from version NULL to 1.0 is

alter domain @extschema(at)(dot)lo set extension lo;
alter function @extschema(at)(dot)lo_oid(lo) set extension lo;
alter function @extschema(at)(dot)lo_manage() set extension lo;

The upgrade script from version 1.0 to 2.0 is, let's say:

CREATE OR REPLACE FUNCTION @extschema(at)(dot)lo_newfunc() …

So the upgrade script from version NULL to 2.0 is:

alter domain @extschema(at)(dot)lo set extension lo;
alter function @extschema(at)(dot)lo_oid(lo) set extension lo;
alter function @extschema(at)(dot)lo_manage() set extension lo;
CREATE OR REPLACE FUNCTION @extschema(at)(dot)lo_newfunc() …

If as an extension author you're kind enough to provide all those 3
scripts and the upgrade setup in the control file, then the user can
issue ALTER EXTENSION lo UPGRADE; and have all your cases covered
automatically.

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support