Rev 4594: Implement a function on btree that inlines the get_parent_map loop. in http://bazaar.launchpad.net/~jameinel/bzr/1.18-faster-iter-ancestry

[John Arbash Meinel]

At http://bazaar.launchpad.net/~jameinel/bzr/1.18-faster-iter-ancestry

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revno: 4594
revision-id: john at arbash-meinel.com-20090806220545-f5dvwvy6tculb64o
parent: pqm at pqm.ubuntu.com-20090806022337-7c2oni07fsjq6gun
committer: John Arbash Meinel <john at arbash-meinel.com>
branch nick: 1.18-faster-iter-ancestry
timestamp: Thu 2009-08-06 17:05:45 -0500
message:
  Implement a function on btree that inlines the get_parent_map loop.
  
  It basically looks for direct parents within a single LeafNode, until it
  hits one that goes outside that node.
  
  Also include some performance notes.
  At least for the number of calls, the new function is *much* better than get_parent_map.
  It takes only 50 calls to walk all of bzr.dev, while for get_parent_map it
  takes 1108 calls.
  Part of that is the 'long tail problem', which is better, albeit not perfect with
  the new function.
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