Re: [Proposal] Fully WAL logged CREATE DATABASE - No Checkpoints

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