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Re: ALTER EXTENSION UPGRADE, v3

From: Dimitri Fontaine <dimitri(at)2ndQuadrant(dot)fr>
To: Itagaki Takahiro <itagaki(dot)takahiro(at)gmail(dot)com>
Cc: Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: ALTER EXTENSION UPGRADE, v3
Date: 2011-02-02 14:45:45
Message-ID: 87bp2u336u.fsf@hi-media-techno.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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

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Next:From: Anssi KääriäinenDate: 2011-02-02 15:08:55
Subject: REVIEW: alter extension upgrade (patch v3)
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