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Re: [PATCH 05/22] read-cache: add index reading api

From
Duy Nguyen <pclouds@gmail.com>
Date
Jul 8, 2013, 12:45 UTC
Message-ID
<CACsJy8CtOWjpxKuNhQXYjPAv8MU0U6yTBEuQeqm0kxqVne6NjQ@mail.gmail.com>
In-Reply-To
<87pputqowr.fsf@gmail.com>
On Mon, Jul 8, 2013 at 6:20 PM, Thomas Gummerer <t.gummerer@gmail.com> wrote:
Show 23 quoted lines
> 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

Previous: Thomas GummererNext: Thomas Gummerer
Message 11 of 51 in “Index v5”
  1. 00/22 Index v5Thomas Gummerer, Jul 7, 2013
  2. 01/22 t2104: Don't fail for index versions other than [23]Thomas Gummerer, Jul 7, 2013
  3. 02/22 read-cache: split index file version specific functionalityThomas Gummerer, Jul 7, 2013
  4. 03/22 read-cache: move index v2 specific functions to their own fileThomas Gummerer, Jul 7, 2013
  5. 04/22 read-cache: Re-read index if index file changedThomas Gummerer, Jul 7, 2013
  6. 05/22 read-cache: add index reading apiThomas Gummerer, Jul 7, 2013
  7. Duy NguyenJul 8, 2013
  8. Thomas GummererJul 8, 2013
  9. Duy NguyenJul 8, 2013
  10. Thomas GummererJul 8, 2013
  11. Duy NguyenJul 8, 2013
  12. Thomas GummererJul 8, 2013
  13. 5/22 Add documentation for the index apiThomas Gummerer, Jul 8, 2013
  14. Duy NguyenJul 9, 2013
  15. Thomas GummererJul 9, 2013
  16. Duy NguyenJul 10, 2013
  17. Thomas GummererJul 11, 2013
  18. Duy NguyenJul 11, 2013
  19. Duy NguyenJul 11, 2013
  20. Junio C HamanoJul 8, 2013
  21. Thomas GummererJul 8, 2013
  22. Junio C HamanoJul 8, 2013
  23. Thomas GummererJul 9, 2013
  24. 06/22 make sure partially read index is not changedThomas Gummerer, Jul 7, 2013
  25. Junio C HamanoJul 8, 2013
  26. Thomas GummererJul 8, 2013
  27. 07/22 dir.c: use index apiThomas Gummerer, Jul 7, 2013
  28. 08/22 tree.c: use index apiThomas Gummerer, Jul 7, 2013
  29. 09/22 name-hash.c: use index apiThomas Gummerer, Jul 7, 2013
  30. 10/22 grep.c: Use index apiThomas Gummerer, Jul 7, 2013
  31. 11/22 ls-files.c: use the index apiThomas Gummerer, Jul 7, 2013
  32. 12/22 read-cache: make read_blob_data_from_index use index apiThomas Gummerer, Jul 7, 2013
  33. 13/22 documentation: add documentation of the index-v5 file formatThomas Gummerer, Jul 7, 2013
  34. Duy NguyenJul 11, 2013
  35. Thomas GummererJul 11, 2013
  36. Duy NguyenJul 11, 2013
  37. Thomas GummererJul 11, 2013
  38. Duy NguyenJul 11, 2013
  39. 14/22 read-cache: make in-memory format aware of stat_crcThomas Gummerer, Jul 7, 2013
  40. 15/22 read-cache: read index-v5Thomas Gummerer, Jul 7, 2013
  41. Eric SunshineJul 7, 2013
  42. Thomas GummererJul 8, 2013
  43. 16/22 read-cache: read resolve-undo dataThomas Gummerer, Jul 7, 2013
  44. 17/22 read-cache: read cache-tree in index-v5Thomas Gummerer, Jul 7, 2013
  45. Eric SunshineJul 7, 2013
  46. 18/22 read-cache: write index-v5Thomas Gummerer, Jul 7, 2013
  47. Eric SunshineJul 7, 2013
  48. 19/22 read-cache: write index-v5 cache-tree dataThomas Gummerer, Jul 7, 2013
  49. 20/22 read-cache: write resolve-undo data for index-v5Thomas Gummerer, Jul 7, 2013
  50. 21/22 update-index.c: rewrite index when index-version is givenThomas Gummerer, Jul 7, 2013
  51. 22/22 p0003-index.sh: add perf test for the index formatsThomas Gummerer, Jul 7, 2013

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