Re: [QUESTION] how to quickly find an oid in the git repository

From: Jeff King <peff@peff.net>
Date: May 30, 2021, 20:54 UTC
Message-ID: <YLP7kuFNfVZK+xCK@coredump.intra.peff.net>
In-Reply-To: <CAOLTT8SS8Wypho7eCCGH7LtOLwM6tWCzp8mGGEVASBC80MwJ5A@mail.gmail.com>

On Sun, May 30, 2021 at 02:53:24PM +0800, ZheNing Hu wrote:

Show 11 quoted lines

> When I tried to make cat-file --batch use ref-filter logic,
> I encountered this problem:
> 
> get_oid_with_context() does not really let me know
> if an oid is in the git repository. E.g.
> 
> get_oid_with_context(the_repository,
> "0000000000000000000000000000000000000000",...)
> 
> will return FOUND. (I really want it to tell me MISSING_OBJECT
> or something else)

Right, it's purely a name->oid lookup.

> On the other hand, oid_object_info_extended() will parse an object
> in depth, using it will seriously affect performance. So I want to know
> if there is a function that can quickly find the oid? I searched in
> `object-name.c`, `object-file.c`, and there seems to be no clue...

You should be able to use oid_object_info_extended() here. It will try to do as little work as possible to fulfill the items requested in the object_info struct. So a blank one (or even passing NULL) will return an error if the object doesn't exist, but not otherwise.

There's also has_object_file(), which is essentially a wrapper for this.

-Peff