Re: initdb caching during tests

> On 5 Aug 2023, at 21:56, Andres Freund <andres@anarazel.de> wrote:

> We have some issues with CI on macos and windows being too expensive (more on
> that soon in a separate email), which reminded me of this thread (with
> original title: [1])
> 
> I've attached a somewhat cleaned up version of the patch to cache initdb
> across runs.  The results are still fairly impressive in my opinion.
> 
> One thing I do not like, but don't have a good idea for how to improve, is
> that there's a bunch of duplicated logic in pg_regress.c and Cluster.pm. I've
> tried to move that into initdb.c itself, but that ends up pretty ugly, because
> we need to be a lot more careful about checking whether options are compatible
> etc. I've also thought about just putting this into a separate perl script,
> but right now we still allow basic regression tests without perl being
> available.  So I concluded that for now just having the copies is the best
> answer.

I had a look at this today and have been running a lot of tests with it without
finding anything that breaks.  The duplicated code is unfortunate, but after
playing around with some options I agree that it's likely the best option.

While looking I did venture down the rabbithole of making it support extra
params as well, but I don't think moving the goalposts there is doing us any
favors, it's clearly chasing diminishing returns.

My only small gripe is that I keep thinking about template databases for CREATE
DATABASE when reading the error messages in this patch, which is clearly not
related to what this does.

+   note("initializing database system by copying initdb template");

I personally would've used cache instead of template in the user facing parts
to keep concepts separated, but thats personal taste.

All in all, I think this is committable as is.

--
Daniel Gustafsson