diff --git a/rhodecode/controllers/compare.py b/rhodecode/controllers/compare.py
--- a/rhodecode/controllers/compare.py
+++ b/rhodecode/controllers/compare.py
@@ -127,7 +127,7 @@ class CompareController(BaseRepoControll
             org_ref = ('rev', rev_start)
             other_ref = ('rev', rev_end)
 
-        c.cs_ranges, discovery_data = PullRequestModel().get_compare_data(
+        c.cs_ranges = PullRequestModel().get_compare_data(
                                     org_repo, org_ref, other_repo, other_ref,
                                     )
 
@@ -156,7 +156,6 @@ class CompareController(BaseRepoControll
         diff_limit = self.cut_off_limit if not fulldiff else None
 
         _diff = diffs.differ(org_repo, org_ref, other_repo, other_ref,
-                             discovery_data,
                              remote_compare=incoming_changesets)
 
         diff_processor = diffs.DiffProcessor(_diff or '', format='gitdiff',
diff --git a/rhodecode/lib/diffs.py b/rhodecode/lib/diffs.py
--- a/rhodecode/lib/diffs.py
+++ b/rhodecode/lib/diffs.py
@@ -704,7 +704,7 @@ class InMemoryBundleRepo(bundlerepositor
         self.bundlefilespos = {}
 
 
-def differ(org_repo, org_ref, other_repo, other_ref, discovery_data=None,
+def differ(org_repo, org_ref, other_repo, other_ref,
            remote_compare=False, context=3, ignore_whitespace=False):
     """
     General differ between branches, bookmarks, revisions of two remote or
@@ -735,7 +735,6 @@ def differ(org_repo, org_ref, other_repo
 
     elif remote_compare:
         opts = diffopts(git=True, ignorews=ignore_whitespace, context=context)
-        common, incoming, rheads = discovery_data
         org_repo_peer = localrepo.locallegacypeer(org_repo.local())
         # create a bundle (uncompressed if other repo is not local)
         if org_repo_peer.capable('getbundle'):
diff --git a/rhodecode/model/pull_request.py b/rhodecode/model/pull_request.py
--- a/rhodecode/model/pull_request.py
+++ b/rhodecode/model/pull_request.py
@@ -155,8 +155,7 @@ class PullRequestModel(BaseModel):
         pull_request.updated_on = datetime.datetime.now()
         self.sa.add(pull_request)
 
-    def _get_changesets(self, alias, org_repo, org_ref, other_repo, other_ref,
-                        discovery_data):
+    def _get_changesets(self, alias, org_repo, org_ref, other_repo, other_ref):
         """
         Returns a list of changesets that are incoming from org_repo@org_ref
         to other_repo@other_ref
@@ -170,7 +169,6 @@ class PullRequestModel(BaseModel):
 
         changesets = []
         #case two independent repos
-        common, incoming, rheads = discovery_data
         if org_repo != other_repo:
             revs = [
                 org_repo._repo.lookup(org_ref[1]),
@@ -223,46 +221,9 @@ class PullRequestModel(BaseModel):
 
         return changesets
 
-    def _get_discovery(self, org_repo, org_ref, other_repo, other_ref):
-        """
-        Get's mercurial discovery data used to calculate difference between
-        repos and refs
-
-        :param org_repo:
-        :type org_repo:
-        :param org_ref:
-        :type org_ref:
-        :param other_repo:
-        :type other_repo:
-        :param other_ref:
-        :type other_ref:
-        """
-
-        _org_repo = org_repo._repo
-        org_rev_type, org_rev = org_ref
-
-        _other_repo = other_repo._repo
-        other_rev_type, other_rev = other_ref
-
-        log.debug('Doing discovery for %s@%s vs %s@%s' % (
-                        org_repo, org_ref, other_repo, other_ref)
-        )
-
-        #log.debug('Filter heads are %s[%s]' % ('', org_ref[1]))
-        org_peer = localrepo.locallegacypeer(_org_repo.local())
-        tmp = discovery.findcommonincoming(
-                  repo=_other_repo,  # other_repo we check for incoming
-                  remote=org_peer,  # org_repo source for incoming
-#                  heads=[_other_repo[other_rev].node(),
-#                         _org_repo[org_rev].node()],
-                  force=True
-        )
-        return tmp
-
     def get_compare_data(self, org_repo, org_ref, other_repo, other_ref):
         """
-        Returns a tuple of incomming changesets, and discoverydata cache for
-        mercurial repositories
+        Returns incomming changesets for mercurial repositories
 
         :param org_repo:
         :type org_repo:
@@ -284,12 +245,7 @@ class PullRequestModel(BaseModel):
         other_repo_scm = other_repo.scm_instance
 
         alias = org_repo.scm_instance.alias
-        discovery_data = [None, None, None]
-        if alias == 'hg':
-            discovery_data = self._get_discovery(org_repo_scm, org_ref,
-                                               other_repo_scm, other_ref)
         cs_ranges = self._get_changesets(alias,
                                          org_repo_scm, org_ref,
-                                         other_repo_scm, other_ref,
-                                         discovery_data)
-        return cs_ranges, discovery_data
+                                         other_repo_scm, other_ref)
+        return cs_ranges