From: Dimitri Fontaine <dimitri@2ndQuadrant.fr>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgreSQL.org,  pgsql-docs@postgreSQL.org
Subject: Re: [HACKERS] "Extension" versus "module"
Organization: 2ndQuadrant
References: <25160.1297664305@sss.pgh.pa.us>
User-Mail-Address: dimitri@2ndQuadrant.fr
Date: Mon, 14 Feb 2011 12:48:26 +0100
In-Reply-To: <25160.1297664305@sss.pgh.pa.us> (Tom Lane's message of "Mon, 14
	Feb 2011 01:18:25 -0500")
Message-ID: <87r5ba4z1x.fsf@2ndQuadrant.fr>
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Tom Lane <tgl@sss.pgh.pa.us> writes:
> Appendix F (contrib.sgml and its subsidiary files) is pretty consistent
> about using "module" to refer to a contrib, uh, module.

I'm now thinking in those terms: the module is the shared object library
that the backend needs to dlopen().  The extension is the SQL level
object that wraps all its components.

> I considered doing a search-and-replace to change this to "extension",
> but I'm not convinced that's a good idea.  I think "extension" means a
> specific kind of SQL object that we just invented, and it's not exactly
> the same concept as "one of those subdirectories under contrib/".  One
> pretty obvious example is that contrib/spi calls itself a module, and
> it's definitely not an extension --- it contains five extensions, none
> of them named "spi".  Another problem is that we'd like to speak of
> upgrading a module from pre-9.1 to 9.1, and in only one of those two
> states is it strictly correct to call it an "extension".  But in some
> sense it's still the same entity.
>
> So I'm not sure whether to change the text at all.  Comments?

+1

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