[postgis-devel] FW: [HACKERS] pg_upgrade changes can it use CREATE EXTENSION?

[Regina Obe]

Thought this note from Tom is relevant to our discussion.



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From: Tom Lane 
Date: Tue, Sep 5, 2017 at 9:22 AM
Subject: Re: [HACKERS] pg_upgrade changes can it use CREATE EXTENSION?
To: Sandro Santilli 

Cc: Regina Obe , PostgreSQL-development 

Sandro Santilli <strk at kbt.io> writes:
> On Wed, Aug 30, 2017 at 06:01:58PM -0400, Tom Lane wrote:
>> We intentionally *don't* do that; pg_dump goes to a lot of trouble to
>> duplicate the old extension contents exactly, instead.  There are a bunch
>> of corner cases that would fail if we allowed the new installation to
>> have different extension contents than the old.  Believe you me, we'd
>> rather have just issued CREATE EXTENSION, but it doesn't work.

> Did you mean `pg_upgrade` ("goes to a lot of trouble") ?

To be precise, pg_dump when working on behalf of pg_upgrade (that is, with
the --binary-upgrade switch).

>> Looking quickly at the thread you cite, I wonder how much of this problem
>> is caused by including version numbers in the library's .so filename.
>> Have you considered not doing that?

> The name change is intentional, to reflect a promise we make between
> patch-level releases but not between minor-level releases. The promise
> to keep C function signatures referenced by SQL objects immutable and
> behavior compatible.

FWIW, I do not think that the library file name is a useful place to
try to enforce such a thing.  Changing the file name creates complications
for upgrade, and it doesn't actually stop you from breaking anything.

                        regards, tom lane