Re: [PATCH v2 6/6] refs/reftable: wire up support for exclude patterns

[Taylor Blau <me@ttaylorr.com>]

On Tue, Sep 17, 2024 at 11:39:04AM +0200, Patrick Steinhardt wrote:
> > Ugh, I just read the next hunk below, so ignore me here ;-).
>
> ;)
>
> I was also wondering whether we'd want to amend the generic parts of the
> refs interface to filter out globs. But it is entirely feasible that a
> backend can indeed filter out globs efficiently, even though none of the
> current ones can. So it kind of makes sense to keep things as-is and let
> the backends themselves decide what they can use.

Yep, agreed.

> > One question I had reading this is why we don't filter these out on the
> > fly in the iterator itself instead of allocating a separate array that
> > we have to xstrdup() into and free later on.
> >
> > We may be at the point of diminishing returns here, but I wonder if
> > allocating this thing is more expensive than a few redundant strcmp()s
> > and calls to is_glob_special(). I dunno.
>
> I think duplicating the array is the right thing to do anyway to not get
> weird lifetime issues with the exclude patterns. A caller may set up a
> ref iterator that they may end up using for longer than they keep alive
> the exlude patterns passed to the iterator. So by duplicating the array
> we might end up wasting a bit of memory, but we avoid such lifetime
> problems completely, which I think is a win to make the infrastructure
> less fragile.

OK, I trust your judgement here over my own as not having nearly the
familiarity with reftables as you do.

Thanks,
Taylor