Date: Sat, 12 Feb 2022 20:17:46 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Andrew Dunstan <andrew@dunslane.net>,
	Dilip Kumar <dilipbalaut@gmail.com>,
	Heikki Linnakangas <hlinnaka@iki.fi>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints
Message-ID: <20220213021746.GM31460@telsasoft.com>
References: 
 <CA+TgmoYdk=tCBtjo_UY08hGpWAqaNYiadodL359+4vUqE8nr4g@mail.gmail.com>
 <202202112108.mmy2r4g7zj7o@alvherre.pgsql>
 <CA+Tgmoa1JiY3r0H_VJMd3Fdi5DDmLHqyJ7EX=F+gyhxAvKvUjg@mail.gmail.com>
 <20220213020044.dh7y4emjhom5jhv6@alap3.anarazel.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220213020044.dh7y4emjhom5jhv6@alap3.anarazel.de>
User-Agent: Mutt/1.9.4 (2018-02-28)
Archived-At: 
 <https://www.postgresql.org/message-id/20220213021746.GM31460%40telsasoft.com>
Precedence: bulk

On Sat, Feb 12, 2022 at 06:00:44PM -0800, Andres Freund wrote:
> Hi,
> 
> On 2022-02-11 16:19:12 -0500, Robert Haas wrote:
> > I somewhat hope we never end up with THREE strategies for creating a new
> > database, but now that I think about it, we might. Somebody might want to
> > use a fancy FS primitive that clones a directory at the FS level, or
> > something.
> 
> I think that'd be a great, and pretty easy to implement, feature. But it seems
> like it'd be mostly orthogonal to the "WAL log data" vs "checkpoint data"
> question? On the primary / single node system using "WAL log data" with "COW
> file copy" would work well.
> 
> I bet using COW file copies would speed up our own regression tests noticeably
> - on slower systems we spend a fair bit of time and space creating template0
> and postgres, with the bulk of the data never changing.
> 
> Template databases are also fairly commonly used by application developers to
> avoid the cost of rerunning all the setup DDL & initial data loading for
> different tests. Making that measurably cheaper would be a significant win.

+1

I ran into this last week and was still thinking about proposing it.

Would this help CI or any significant fraction of buildfarm ?
Or just tests run locally on supporting filesystems.

Note that pg_upgrade already supports copy/link/clone.  (Obviously, link
wouldn't do anything desirable for CREATE DATABASE).

-- 
Justin