[PATCH 01 of 15] hgext: `speedy` - the history query accelerator

[Pierre-Yves David]

On Tue, Dec 11, 2012 at 10:38:16AM -0800, Tomasz Kleczek wrote:
> # HG changeset patch
> # User Tomasz Kleczek <tkleczek at fb.com>
> # Date 1355250659 28800
> # Branch stable
> # Node ID 13c6bcb8dd900dc7dbf5e3da9ef68d56fed250b3
> # Parent  8973e7dd92d5afdeb82e91d5b66934d53a74e8da
> hgext: `speedy` - the history query accelerator
> 
> This is the first in a series of patches that address the problem
> of hg log being slow on a big repo in most cases.
> 
> 
> Many history queries have performance linear in the number of commits
> or even worse - the size of manifest.
> 
> As a result almost every hg log query with non-trivial rev range or
> with directory specified is painfully slow on big repositories
> and its poor performance doesn't depend on actual output size.
> 
> Here are some frequently used commands that just print a handful of
> log messages:
>   * hg log dir_with_few_commits
>   * hg log --rev "user(MyLazyFriend)"
> 
> They may take more then 30 secs on a big repo (with couple hundred
> thousands of commits).
> 
> This extension addresses this problem by introducing a server component
> that maintains indices over the history and uses them to respond to queries
> in an efficient manner.
> 
> What is going on:
> 
> * the client component forwards certain history queries to the server
>   and waits for a response
> * it takes into account that its history may have diverged from
>   the server's, and still gives correct answers
> * if the server doesn't respond fast enough or crashes, the client falls
>   back to computing the answer locally using normal code path
> * extension setup time is neglible and there is no overhead for queries
>   that cannot be accelerated by the server
> 
> The server can be run:
> * locally in the same process as client or

Could you includes some numbers about this local version ?

It sound like it could have interresting application within graphical history
viewer like TortoiseHG or hgview. Those qre long lived process that can absorbs
the setup time and benefit from the speed up.

-- 
Pierre-Yves David