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From: Duy Nguyen <pclouds@gmail.com>
To: Thomas Gummerer <t.gummerer@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Thomas Rast <trast@inf.ethz.ch>,
	Michael Haggerty <mhagger@alum.mit.edu>,
	Junio C Hamano <gitster@pobox.com>,
	Robin Rosenberg <robin.rosenberg@dewire.com>
Subject: Re: [PATCH 05/22] read-cache: add index reading api
Date: Mon, 8 Jul 2013 19:45:39 +0700	[thread overview]
Message-ID: <CACsJy8CtOWjpxKuNhQXYjPAv8MU0U6yTBEuQeqm0kxqVne6NjQ@mail.gmail.com> (raw)
In-Reply-To: <87pputqowr.fsf@gmail.com>

On Mon, Jul 8, 2013 at 6:20 PM, Thomas Gummerer <t.gummerer@gmail.com> wrote:
> Duy Nguyen <pclouds@gmail.com> writes:
>> Putting filter_opts in index_state feels like a bad design. Iterator
>> information should be separated from the iterated object, so that two
>> callers can walk through the same index without stepping on each other
>> (I'm not talking about multithreading, a caller may walk a bit, then
>> the other caller starts walking, then the former caller resumes
>> walking again in a call chain).
>
> Yes, you're right.  We need the filter_opts to see what part of the
> index has been loaded [1] and which part has been skipped, but it
> shouldn't be used for filtering in the for_each_index_entry function.
>
> I think there should be two versions of the for_each_index_entry
> function then, where the for_each_index_entry function would behave the
> same way as the for_each_index_entry_filtered function with the
> filter_opts parameter set to NULL:
> for_each_index_entry_filtered(struct index_state *, each_cache_entry_fn, void *cb_data, struct filter_opts *)
> for_each_index_entry(struct index_state *, each_cache_entry_fn, void *cb_data)
>
> Both of them then should call index_change_filter_opts to make sure all
> the entries that are needed are loaded in the in-memory format.
>
> Does that make sense?

Hmm.. I was confused actually (documentation on the api would help
greatly). If you already filter at load time, I don't think you need
to match again. The caller asked for filter and it should know what's
in there so for_each_index_entry just goes through all entries without
extra match_pathspec. Or is that what next_index_entry for?
match_pathspec function could be expensive when glob is involved. If
the caller wants extra matching, it could do inside the callback
function.

It seems you could change the filter with index_change_filter_opts. In
v5 the index will be reloaded. What happens when some index entries
area already modified? Do we start to have read-only index "views" and
one read-write view? If partial views are always read-only, perhaps we
just allow the user to create a new index_state (or view) with new
filter and destroy the old one. We don't have to care about changing
or separating filter in that case because the view is the iterator.

I wanted to have a tree-based iterator api, but that seems
incompatible with pre-v5 (or at least adds some overhead on pre-v5 to
rebuild the tree structure). It looks like using pathspec to build a
list of entries, as you did, is a good way to take advantage of
tree-based v5 while maintaining code compatibility with pre-v5. By the
way with tree structure, you could use tree_entry_interesting in
read_index_filtered_v5. I think it's more efficient than
match_pathspec.

I'm still studying the code. Some of what I wrote here may be totally
wrong due to my lack of understanding. I'll get back to you later if I
find something else.

> [1] That is only important for the new index-v5 file format, which can
>     be loaded partially.  The filter_opts could always be set to NULL,
>     as the whole index is always loaded anyway.
--
Duy

  reply	other threads:[~2013-07-08 12:46 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-07  8:11 [PATCH 00/22] Index v5 Thomas Gummerer
2013-07-07  8:11 ` [PATCH 01/22] t2104: Don't fail for index versions other than [23] Thomas Gummerer
2013-07-07  8:11 ` [PATCH 02/22] read-cache: split index file version specific functionality Thomas Gummerer
2013-07-07  8:11 ` [PATCH 03/22] read-cache: move index v2 specific functions to their own file Thomas Gummerer
2013-07-07  8:11 ` [PATCH 04/22] read-cache: Re-read index if index file changed Thomas Gummerer
2013-07-07  8:11 ` [PATCH 05/22] read-cache: add index reading api Thomas Gummerer
2013-07-08  2:01   ` Duy Nguyen
2013-07-08 11:40     ` Thomas Gummerer
2013-07-08  2:19   ` Duy Nguyen
2013-07-08 11:20     ` Thomas Gummerer
2013-07-08 12:45       ` Duy Nguyen [this message]
2013-07-08 13:37         ` Thomas Gummerer
2013-07-08 20:54         ` [PATCH 5.5/22] Add documentation for the index api Thomas Gummerer
2013-07-09 15:42           ` Duy Nguyen
2013-07-09 20:10             ` Thomas Gummerer
2013-07-10  5:28               ` Duy Nguyen
2013-07-11 11:30                 ` Thomas Gummerer
2013-07-11 11:42                   ` Duy Nguyen
2013-07-11 12:27                     ` Duy Nguyen
2013-07-08 16:36   ` [PATCH 05/22] read-cache: add index reading api Junio C Hamano
2013-07-08 20:10     ` Thomas Gummerer
2013-07-08 23:09       ` Junio C Hamano
2013-07-09 20:13         ` Thomas Gummerer
2013-07-07  8:11 ` [PATCH 06/22] make sure partially read index is not changed Thomas Gummerer
2013-07-08 16:31   ` Junio C Hamano
2013-07-08 18:33     ` Thomas Gummerer
2013-07-07  8:11 ` [PATCH 07/22] dir.c: use index api Thomas Gummerer
2013-07-07  8:11 ` [PATCH 08/22] tree.c: " Thomas Gummerer
2013-07-07  8:11 ` [PATCH 09/22] name-hash.c: " Thomas Gummerer
2013-07-07  8:11 ` [PATCH 10/22] grep.c: Use " Thomas Gummerer
2013-07-07  8:11 ` [PATCH 11/22] ls-files.c: use the " Thomas Gummerer
2013-07-07  8:11 ` [PATCH 12/22] read-cache: make read_blob_data_from_index use " Thomas Gummerer
2013-07-07  8:11 ` [PATCH 13/22] documentation: add documentation of the index-v5 file format Thomas Gummerer
2013-07-11 10:39   ` Duy Nguyen
2013-07-11 11:39     ` Thomas Gummerer
2013-07-11 11:47       ` Duy Nguyen
2013-07-11 12:26         ` Thomas Gummerer
2013-07-11 12:50           ` Duy Nguyen
2013-07-07  8:11 ` [PATCH 14/22] read-cache: make in-memory format aware of stat_crc Thomas Gummerer
2013-07-07  8:11 ` [PATCH 15/22] read-cache: read index-v5 Thomas Gummerer
2013-07-07 20:18   ` Eric Sunshine
2013-07-08 11:40     ` Thomas Gummerer
2013-07-07  8:11 ` [PATCH 16/22] read-cache: read resolve-undo data Thomas Gummerer
2013-07-07  8:11 ` [PATCH 17/22] read-cache: read cache-tree in index-v5 Thomas Gummerer
2013-07-07 20:41   ` Eric Sunshine
2013-07-07  8:11 ` [PATCH 18/22] read-cache: write index-v5 Thomas Gummerer
2013-07-07 20:43   ` Eric Sunshine
2013-07-07  8:11 ` [PATCH 19/22] read-cache: write index-v5 cache-tree data Thomas Gummerer
2013-07-07  8:11 ` [PATCH 20/22] read-cache: write resolve-undo data for index-v5 Thomas Gummerer
2013-07-07  8:11 ` [PATCH 21/22] update-index.c: rewrite index when index-version is given Thomas Gummerer
2013-07-07  8:12 ` [PATCH 22/22] p0003-index.sh: add perf test for the index formats Thomas Gummerer

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