From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Nikolay Shaplov <n.shaplov@postgrespro.ru>, pgsql-hackers@postgresql.org
Subject: Re: [PROPOSAL] Move all am-related reloption code into
 src/backend/access/[am-name] and get rid of relopt_kind
In-reply-to: <20160527190558.GA703687@alvherre.pgsql>
References: <20160527190558.GA703687@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Fri, 27 May 2016 15:05:58 -0400"
Date: Fri, 27 May 2016 16:13:04 -0400
Message-ID: <20879.1464379984@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> Nikolay Shaplov wrote:
>> Story start from the point that I found out that a.m. can not forbid changing 
>> some of it's reloptions with ALTER INDEX command.

> Hmm, this sounds like a bug to me.  In BRIN, if you change the
> pages_per_range option for an existing index, the current index
> continues to work because the value used during the last index build is
> stored in the metapage.  Only when you reindex after changing the option
> the new value takes effect.

> I think Bloom should do likewise.

AFAICT, Bloom *does* do that.  The reloptions are only consulted directly
while initializing the metapage.

I think Nikolay's complaint is essentially that there should be a way
for an AM to forbid ALTER INDEX if it's not going to support on-the-fly
changes of a given reloption.  That might be a helpful usability
improvement, but it's only a usability improvement not a bug fix.

			regards, tom lane


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