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From: Jeff King <peff@peff.net>
To: Derrick Stolee <dstolee@microsoft.com>
Cc: git@vger.kernel.org, gitster@pobox.com, stolee@gmail.com,
	ramsay@ramsayjones.plus.com, sbeller@google.com
Subject: Re: [PATCH v4 4/4] sha1_name: minimize OID comparisons during disambiguation
Date: Mon, 9 Oct 2017 09:49:33 -0400
Message-ID: <20171009134933.vmba67adelqbkx4y@sigill.intra.peff.net> (raw)
In-Reply-To: <20171008184942.69444-5-dstolee@microsoft.com>

On Sun, Oct 08, 2017 at 02:49:42PM -0400, Derrick Stolee wrote:

> @@ -505,6 +506,65 @@ static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
>  	return 0;
>  }
>  
> +static void find_abbrev_len_for_pack(struct packed_git *p,
> +				     struct min_abbrev_data *mad)
> +{
> +	int match = 0;
> +	uint32_t num, last, first = 0;
> +	struct object_id oid;
> +
> +	open_pack_index(p);
> +	num = p->num_objects;
> +	last = num;
> +	while (first < last) {
> [...]

Your cover letter lists:

  * Silently skip packfiles that fail to open with open_pack_index()

as a change from the previous version. But this looks the same as the
last round. I think this _does_ end up skipping such packfiles because
p->num_objects will be zero. Is it worth having a comment to that
effect (or even just an early return) to make it clear that the
situation is intentional?

Although...

> +	/*
> +	 * first is now the position in the packfile where we would insert
> +	 * mad->hash if it does not exist (or the position of mad->hash if
> +	 * it does exist). Hence, we consider a maximum of three objects
> +	 * nearby for the abbreviation length.
> +	 */
> +	mad->init_len = 0;
> +	if (!match) {
> +		nth_packed_object_oid(&oid, p, first);
> +		extend_abbrev_len(&oid, mad);

If we have zero objects in the pack, what would nth_packed_object_oid()
be returning here?

So I actually think we do want an early return, not just when
open_packed_index() fails, but also when p->num_objects is zero.

-Peff

  reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-08 18:49 [PATCH v4 0/4] Improve abbreviation disambiguation Derrick Stolee
2017-10-08 18:49 ` [PATCH v4 1/4] p4211-line-log.sh: add log --online --raw --parents perf test Derrick Stolee
2017-10-08 18:49 ` [PATCH v4 2/4] sha1_name: unroll len loop in find_unique_abbrev_r Derrick Stolee
2017-10-08 18:49 ` [PATCH v4 3/4] sha1_name: parse less while finding common prefix Derrick Stolee
2017-10-09 13:42   ` Jeff King
2017-10-08 18:49 ` [PATCH v4 4/4] sha1_name: minimize OID comparisons during disambiguation Derrick Stolee
2017-10-09 13:49   ` Jeff King [this message]
2017-10-10 12:16     ` Derrick Stolee
2017-10-10 12:36       ` Jeff King
2017-10-10 12:56         ` Junio C Hamano
2017-10-10 13:09           ` Jeff King
2017-10-10 13:11           ` Derrick Stolee
2017-10-10 13:30             ` Jeff King
2017-10-11 13:58               ` Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 0/4] Improve abbreviation disambiguation Derrick Stolee
2017-10-12 12:04                   ` Derrick Stolee
2017-10-12 12:21                     ` Junio C Hamano
2017-10-12 14:22                       ` Jeff King
2017-10-12 12:02                 ` [PATCH v5 1/4] p4211-line-log.sh: add log --online --raw --parents perf test Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 2/4] sha1_name: unroll len loop in find_unique_abbrev_r Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 3/4] sha1_name: parse less while finding common prefix Derrick Stolee
2017-10-12 12:02                 ` [PATCH v5 4/4] sha1_name: minimize OID comparisons during disambiguation Derrick Stolee

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