Re: QGit: Shrink used memory with custom git log format

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Mon, 26 Nov 2007, Shawn O. Pearce wrote:

> Marco Costalba <mcostalba@gmail.com> wrote:
> > Now instead of --pretty=raw a custom made --pretty=format is given,
> > this shrinks loaded data of 30% (17MB less on Linux tree) and gives a
> > good speed up when you are low on memory (especially on big repos)
> > 
> > Next step _would_ be to load log message body on demand (another 50%
> > reduction) but this has two drawbacks:
> > 
> > (1) Text search/filter on log message would be broken
> > 
> > (2) Slower to browse through revisions because for each revision an
> > additional git-rev-list /git-log command should be executed to read
> > the body
> > 
> > The second point is worsted by the fact that it is not possible to
> > keep a command running and "open" like as example git-diff-tree
> > --stdin and feed with additional revision's sha when needed. Avoiding
> > the burden to startup a new process each time to read a new log
> > message given an sha would let the answer much more quick especially
> > on lesser OS's
> > 
> > Indeed there is a git-rev-list --stdin option but with different
> > behaviour from git-diff-tree --stdin and not suitable for this.
> 
> There was a proposed patch for git-cat-file that would let you run
> it in a --stdin mode; the git-svn folks wanted this to speed up
> fetching raw objects from the repository.  That may help as you
> could get commit bodies (in raw format - not reencoded format!)
> quite efficiently.
> 
> Otherwise I think what you really want here is a libgit that you can
> link into your process and that can efficiently inflate an object
> on demand for you.  Like the work Luiz was working on this past
> summer for GSOC.  Lots of downsides to that current tree though...
> like die() kills the GUI...

But then, die() calls die_routine, which you can override.  And C++ has 
this funny exception mechanism which just begs to be used here.  The only 
thing you need to add is a way to flush all singletons like the object 
array.

Ciao,
Dscho