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Re: RFC: Another proposed hash function transition plan




David Lang wrote:

>> Translation table
>> ~~~~~~~~~~~~~~~~~
>> A fast bidirectional mapping between sha1-names and sha256-names of
>> all local objects in the repository is kept on disk. The exact format
>> of that mapping is to be determined.
>>
>> All operations that make new objects (e.g., "git commit") add the new
>> objects to the translation table.
>
> This seems like a rather nontrival thing to design. It will need to
> hold millions of mappings, and be quickly searchable from either
> direction (sha1->new and new->sha1) while still be fairly fast to
> insert new records into.

I am currently thinking of using LevelDB, since it has the advantages of
being simple, already existing, and having already been ported to Java
(allowing JGit can read and write the same format).

If that doesn't work, we'd try some other key-value store like Samba's
tdb or Kyoto Cabinet.

Jonathan