Re: ci: namespace ccache by PostgreSQL major version

Hi,

On 2026-07-17 08:27:39 -0700, Jacob Champion wrote:
> On Fri, Jul 17, 2026 at 6:06 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > That's how it works. We restore the cache for master and for the current
> > branch. We save the cache, after pruning it, for the current branch iff the
> > hit rate was < 80%.
> >
> > It'd be nice if we could restore the cache for the "base branch" of a branch,
> > instead of master, but that's not currently possible in GHA, from what I can
> > tell. Only caches on the default branch are accessible to other branches.
>
> Quick tangent: is there a reason we put the refname into the cache
> key? It seems like some of the logic there would happen by default if
> we used the same cache prefix for all branches, since I thought GitHub
> would perform the fallback-to-default-branch for us.

For cfbot it's kinda important to have *both* the master and branch specific
caches for a run. Often, after a rebase of a branch to a newer master, the
branch specific key will have a lower hit rate than during the last run, but
master's cache applies to a lot of the part of the build not modified by the
branch.

I also have some hope that eventually github will allow using caches from more
than just the default branch. For testing to-be-backpatched bug fixes - on fix
specific, per-major branches, it's pretty painful that they can only start
with master's cache.

Greetings,

Andres Freund