Re: [RFC/PATCH 0/8] Add configuration options for split-index

On Tue, Jul 12, 2016 at 6:01 PM, Duy Nguyen [off-list ref] wrote:

On Mon, Jul 11, 2016 at 7:22 PM, Christian Couder
[off-list ref] wrote:

quoted

Future work
~~~~~~~~~~~

One thing that is probably missing is a mechanism to avoid having too
many changes accumulating in the (split) index while in split index
mode. The git-update-index documentation says:

        If split-index mode is already enabled and `--split-index` is
        given again, all changes in $GIT_DIR/index are pushed back to
        the shared index file.

but it is probably better to not expect the user to think about it and
to have a mechanism that pushes back all changes to the shared index
file automatically when some threshold is reached. The threshold could
be for example when $GIT_DIR/index size is larger than 25% of the
shared index size. Opinions, test results or test ideas are welcome on
this.

Oh yes I would like something like this. I stuck to the basics because
as you see you need to define some criteria to re-split again, but
without experimenting on real repos, I could just have gone the wrong
way. Index file size or the percentage of entries in linked/shared
indexes are two good candidates.

Ok, I started working on automatically pushing back all changes to the
shared index when the percentage of entries in linked vs shared
indexes is greater than 25% (maybe I will make it configurable later).
It is very basic and doesn't work well for now (for one thing it is
missing added entries), see:

https://github.com/chriscool/git/commits/config-split-index8

Basically I would like a way to count then entries that are only in
the linked index without modifying them to be safe, but I have a hard
time seeing how I could modify prepare_to_write_split_index() to get
that.

You can also just re-split on
commands that likely lead to increasing linked index size a lot (maybe
git-reset), or run long enough that some extra processing won't get
noticed. For example git-gc should definitely re-split if this feature
is on, but I can't say if it's often enough.

I'd like to avoid re-split only on some specific commands as I feel it
could lead to bad behavior when none of these specific commands are
called but the linked index is growing because of other commands.