Subject: Re: AdvanceXLInsertBuffer vs. WAL segment compressibility
To: Michael Paquier <michael.paquier@gmail.com>,
 Amit Kapila <amit.kapila16@gmail.com>
References: <579297F8.7020107@anastigmatix.net>
 <CAA4eK1L7UvOS8TpUvoMuGZ4Mid=Mef-Cq5Q0M-2oYSHC-CSikw@mail.gmail.com>
 <57962061.9010506@anastigmatix.net>
 <CAB7nPqQ5NS5E-rWzd76MQHBEoc5cGHjSrUs4W6EiTxwWEx338Q@mail.gmail.com>
 <5796D9EB.6070407@anastigmatix.net>
 <CAA4eK1K_qmdeVoitjY0vyLcEBRu=o5Mwqz-+6hA+nG=KnS_kHA@mail.gmail.com>
 <CAB7nPqQGwCFHin5aTY6FVEHOKW_LvHQi2LJAd0=7RmoHiSZJnw@mail.gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
From: Chapman Flack <chap@anastigmatix.net>
Message-ID: <5797FE50.7070600@anastigmatix.net>
Date: Tue, 26 Jul 2016 20:20:32 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.7.0
MIME-Version: 1.0
In-Reply-To: 
 <CAB7nPqQGwCFHin5aTY6FVEHOKW_LvHQi2LJAd0=7RmoHiSZJnw@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

On 07/26/16 20:01, Michael Paquier wrote:
> On Tue, Jul 26, 2016 at 9:48 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> Does any body else see the use case
>> reported by Chapman important enough that we try to have some solution
>> for it in-core?
> 
> The lack of updates in the pg_lesslog project is a sign that it is not
> that much used. I does not seem a good idea to bring in-core a tool
> not used that much by users.

Effectively, it already was brought in-core in commit 9a20a9b.
Only, that change had an unintended consequence that *limits*
compressibility - and it would not have that consequence, if
it were changed to simply set xlp_pageaddr to InvalidXLogRecPtr
in the dummy zero pages written to fill out a segment.

-Chap


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers