# HG changeset patch
# User Augie Fackler <augie@google.com>
# Date 1449243298 18000
# Node ID c08814b48ae52b69dc032318c95ce50fa6a5e791
# Parent  b0d90fef16b616632bcc4d96eef0a4e778eb530b
changegroup: avoid iterating the whole manifest

The old code gathered the list of all files that changed anywhere in
history and then gathered changed file nodes by walking the entirety
of each manifest to be sent in order to gather changed file
nodes. That's going to be unfortunate for narrowhg, and it's already
inefficient for medium-to-large repositories.

Timings for bundle --all on my hg repo, tested with hgperf:
Before:
! wall 23.442445 comb 23.440000 user 23.250000 sys 0.190000 (best of 3)

After:
! wall 20.272187 comb 20.270000 user 20.190000 sys 0.080000 (best of 3)

diff -r b0d90fef16b6 -r c08814b48ae5 mercurial/changegroup.py
--- a/mercurial/changegroup.py	Fri Dec 04 15:59:46 2015 -0500
+++ b/mercurial/changegroup.py	Fri Dec 04 10:34:58 2015 -0500
@@ -613,7 +613,8 @@
         clrevorder = {}
         mfs = {} # needed manifests
         fnodes = {} # needed file nodes
-        changedfiles = set()
+        # maps manifest node id -> set(changed files)
+        mfchangedfiles = {}
 
         # Callback for the changelog, used to collect changed files and manifest
         # nodes.
@@ -621,9 +622,12 @@
         def lookupcl(x):
             c = cl.read(x)
             clrevorder[x] = len(clrevorder)
-            changedfiles.update(c[3])
+            n = c[0]
             # record the first changeset introducing this manifest version
-            mfs.setdefault(c[0], x)
+            mfs.setdefault(n, x)
+            # Record a complete list of potentially-changed files in
+            # this manifest.
+            mfchangedfiles.setdefault(n, set()).update(c[3])
             return x
 
         self._verbosenote(_('uncompressed size of bundle content:\n'))
@@ -668,8 +672,12 @@
             clnode = mfs[x]
             if not fastpathlinkrev:
                 mdata = ml.readfast(x)
-                for f, n in mdata.iteritems():
-                    if f in changedfiles:
+                for f in mfchangedfiles[x]:
+                    if True:
+                        try:
+                            n = mdata[f]
+                        except KeyError:
+                            continue
                         # record the first changeset introducing this filelog
                         # version
                         fclnodes = fnodes.setdefault(f, {})
@@ -696,6 +704,9 @@
                 return dict(genfilenodes())
             return fnodes.get(fname, {})
 
+        changedfiles = set()
+        for x in mfchangedfiles.itervalues():
+            changedfiles.update(x)
         for chunk in self.generatefiles(changedfiles, linknodes, commonrevs,
                                         source):
             yield chunk