What is an efficient way to get all blobs / trees that have notes attached?

> Hi,
>
> I'm curious whether there's a more efficient way to get a list of blobs /
> trees (and their names) that have notes attached than doing this:
>
> 1) Get all notes refs I'm interested in (git-for-each-ref).
>
> 2) For each notes ref, get the list of notes (git-notes list) and store them
> in a hash table that maps object hashes to notes.
>
> 3) Recursively list all blobs / trees (git-ls-tree) and look whether an
> object's hash is conatined in our table to get its notes.
>
> In particular 3) could be expensive for repos with a lot of files as we're
> looking at all of them just to see whether they have notes attached.

> for notes_ref in $(git for-each-ref refs/notes | cut -c 49-)
> do
>     echo "--- $notes_ref ---"
>     for annotated_obj in $(git notes --ref=$notes_ref list | cut -c 41-)
>     do
>         type=$(git cat-file -t "$annotated_obj")
>         if test "$type" != "commit"
>         then
>             echo "$annotated_obj: $type"
>         fi
>     done
> done
>
> Can probably be made even faster by using the --batch option to cat-file...

>> 3) Recursively list all blobs / trees (git-ls-tree) and look whether an
>> object's hash is conatined in our table to get its notes.
>>
>> In particular 3) could be expensive for repos with a lot of files as we're
>> looking at all of them just to see whether they have notes attached.
>
> In (3), why would you need to search through _all_ blobs/trees? Would
> it not be cheaper to simply query the object type of each annotated
> object from (2)? I.e. something like:
>
> for notes_ref in $(git for-each-ref refs/notes | cut -c 49-)
> do
>     echo "--- $notes_ref ---"
>     for annotated_obj in $(git notes --ref=$notes_ref list | cut -c 41-)
>     do
>         type=$(git cat-file -t "$annotated_obj")
>         if test "$type" != "commit"
>         then
>             echo "$annotated_obj: $type"
>         fi
>     done
> done

> On Fri, Apr 1, 2016 at 2:16 PM, Johan Herland <johan@herland.net> wrote:
>>> 3) Recursively list all blobs / trees (git-ls-tree) and look whether an
>>> object's hash is conatined in our table to get its notes.
>>>
>>> In particular 3) could be expensive for repos with a lot of files as we're
>>> looking at all of them just to see whether they have notes attached.
>>
>> In (3), why would you need to search through _all_ blobs/trees? Would
>> it not be cheaper to simply query the object type of each annotated
>> object from (2)? I.e. something like:
>>
>> for notes_ref in $(git for-each-ref refs/notes | cut -c 49-)
>> do
>>     echo "--- $notes_ref ---"
>>     for annotated_obj in $(git notes --ref=$notes_ref list | cut -c 41-)
>>     do
>>         type=$(git cat-file -t "$annotated_obj")
>>         if test "$type" != "commit"
>>         then
>>             echo "$annotated_obj: $type"
>>         fi
>>     done
>> done
>
> Thanks for the idea. The problem is that I do want to list the notes
> by path of the object they belong to. As a blob could potentially
> belong to more than one path (copies of files in the repo), I do not
> see another way of getting that information other than iterating over
> all blobs and checking what path(s) they belong to.