Re: [PATCH v1 00/19] Add configuration options for split-index

From: Duy Nguyen <pclouds@gmail.com>
Date: Oct 26, 2016, 09:25 UTC
Message-ID: <CACsJy8Ba0BY=pZwrKf5rcD5AaZ3YyKh9=ENKkj7hHpTqh00OnA@mail.gmail.com>
In-Reply-To: <xmqqk2cws5t6.fsf@gitster.mtv.corp.google.com>

On Wed, Oct 26, 2016 at 12:21 AM, Junio C Hamano <gitster@pobox.com> wrote:

Show 9 quoted lines

>> Timestamps allow us to say, ok this base index file has not been read
>> by anybody for N+ hours (or better, days), it's most likely not
>> referenced by any temporary index files (including
>> $GIT_DIR/index.lock) anymore because those files, by the definition of
>> "temporary", must be gone by now....
>
> and if we guessed wrong, users will have a "temporary index" that
> they meant to keep for longer term that is now broken here.  I am
> not sure if that risk is worth taking.

Even if we ignore user index files (by forcing them all to be stored in one piece), there is a problem with the special temporary file index.lock, which must use split-index because it will become the new index. Handling race conditions could be tricky with ref counting. Timestamps help in this regard.

-- 
Duy