Speedup with history-db (was: Performance improvements for bzr-2.4 on large trees)

[Eli Zaretskii]

> Date: Fri, 27 May 2011 12:23:45 +0300
> From: Eli Zaretskii <eliz at gnu.org>
> Cc: bazaar at lists.canonical.com
> 
> A few comments:

Here's one more:  I just did a "bzr up", which announced that the tree
is up to date.  And yet history-db did do something, as this portion
of the log shows:

  8.656  fetch up to rev {rgm at gnu.org-20110527071815-pnm36i0e38mb8wte}
  13.578  history_db post-change-hook took 1.638s (0.012s to get_config, 1.526s to init, 0.100s to import)
  13.578  Stats:
  {'num_search_tips': 0,
   'step mainline': 1,
   'step mainline added': 4,
   'step mainline cache missed': 1,
   'step mainline initial': 1}
  [ 4216] 2011-05-27 17:06:14.640 INFO: Tree is up to date at revision 104384 of branch bzr+ssh://eliz@bzr.savannah.gnu.org/emacs/trunk

What is it trying to do for 1.6s?