To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Simon Riggs <simon@2ndQuadrant.com>,
	Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>,
	ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>,
	pgsql-hackers@postgresql.org
Subject: Re: rmgr hooks and contrib/rmgr_hook
In-Reply-To: <24006.1221483138@sss.pgh.pa.us> (Tom Lane's message of "Mon\,
	15 Sep 2008 08\:52\:18 -0400")
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	<1220345064.4371.275.camel@ebony.2ndQuadrant>
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	<1220348980.4371.316.camel@ebony.2ndQuadrant>
	<14451.1220369969@sss.pgh.pa.us>
	<1220372673.4371.465.camel@ebony.2ndQuadrant>
	<48CB72C8.1070700@enterprisedb.com>
	<1221470800.3913.1229.camel@ebony.2ndQuadrant>
	<87sks1oi4o.fsf@oxford.xeocode.com> <24006.1221483138@sss.pgh.pa.us>
From: Gregory Stark <stark@enterprisedb.com>
Organization: EnterpriseDB
Date: Mon, 15 Sep 2008 14:28:06 +0100
Message-ID: <877i9do7x5.fsf@oxford.xeocode.com>
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Tom Lane <tgl@sss.pgh.pa.us> writes:

> Gregory Stark <stark@enterprisedb.com> writes:
>> Simon Riggs <simon@2ndQuadrant.com> writes:
>>> Indexes have always been able to be added dynamically. Now they can be
>>> recovered correctly as well.
>
>> Hm, so currently if you want to add a new indexam you can't just insert into
>> pg_am and make them recoverable. You basically have to build in your new index
>> access method into Postgres with the new rmgr. That is annoying and a problem
>> worth tackling.
>
> I concur with Heikki that that's not exactly a compelling use-case.
> I've never heard of anyone building a non-core index AM at all; much
> less trying to use it in a production context.  Given the obvious
> potential for version-mismatch-type problems, it's hard to believe
> that anyone ever would try.

Well wasn't GIST such an instance until we put it in core? IIRC it lived in
contrib for a long time. It happens that the route they took was to implement
it without recoverability until it was in core then add logging. I suspect we
would lean on any new method to have logging before it was merged in though.

I think the version-mismatch problems are fairly important though which is why
I was suggesting providing checks for that in postgres. Simon's right though
that the plugin could check for it itself.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Ask me about EnterpriseDB's Slony Replication support!