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From kocol...@apache.org
Subject couch commit: updated refs/heads/2735-duplicate-docs to cb4f1aa
Date Sat, 18 Jul 2015 11:51:16 GMT
Repository: couchdb-couch
Updated Branches:
  refs/heads/2735-duplicate-docs [created] cb4f1aa07


Ensure doc groups are sorted before merging them

We had been implicily assuming that clients send us sorted groups, but
unsurprisingly that's not always the case. The additional sorting here
should be redundant, but the consequences of merging unsorted groups are
severe -- we can end up with uniqueness violations on the primary key in
the database -- and so we add an additional sort here.

COUCHDB-2735


Project: http://git-wip-us.apache.org/repos/asf/couchdb-couch/repo
Commit: http://git-wip-us.apache.org/repos/asf/couchdb-couch/commit/cb4f1aa0
Tree: http://git-wip-us.apache.org/repos/asf/couchdb-couch/tree/cb4f1aa0
Diff: http://git-wip-us.apache.org/repos/asf/couchdb-couch/diff/cb4f1aa0

Branch: refs/heads/2735-duplicate-docs
Commit: cb4f1aa073a6add3b4a6215ab2d253bff8e8c961
Parents: 331f811
Author: Adam Kocoloski <adam@cloudant.com>
Authored: Sat Jul 18 07:49:00 2015 -0400
Committer: Adam Kocoloski <adam@cloudant.com>
Committed: Sat Jul 18 07:49:31 2015 -0400

----------------------------------------------------------------------
 src/couch_db_updater.erl | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/couchdb-couch/blob/cb4f1aa0/src/couch_db_updater.erl
----------------------------------------------------------------------
diff --git a/src/couch_db_updater.erl b/src/couch_db_updater.erl
index bd42b35..92139a9 100644
--- a/src/couch_db_updater.erl
+++ b/src/couch_db_updater.erl
@@ -276,7 +276,7 @@ handle_cast(Msg, #db{name = Name} = Db) ->
 
 handle_info({update_docs, Client, GroupedDocs, NonRepDocs, MergeConflicts,
         FullCommit}, Db) ->
-    GroupedDocs2 = maybe_tag_grouped_docs(Client, GroupedDocs),
+    GroupedDocs2 = sort_and_tag_grouped_docs(Client, GroupedDocs),
     if NonRepDocs == [] ->
         {GroupedDocs3, Clients, FullCommit2} = collect_updates(GroupedDocs2,
                 [Client], MergeConflicts, FullCommit);
@@ -338,10 +338,15 @@ handle_info({'DOWN', Ref, _, _, Reason}, #db{fd_monitor=Ref, name=Name}
= Db) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
-maybe_tag_grouped_docs(Client, GroupedDocs) ->
+sort_and_tag_grouped_docs(Client, GroupedDocs) ->
+    % These groups should already be sorted but sometimes clients misbehave.
+    % The merge_updates function will fail and the database can end up with
+    % duplicate documents if the incoming groups are not sorted, so as a sanity
+    % check we sort them again here. See COUCHDB-2735.
+    Cmp = fun([#doc{id=A}|_], [#doc{id=B}|_]) -> A < B end,
     lists:map(fun(DocGroup) ->
         [{Client, maybe_tag_doc(D)} || D <- DocGroup]
-    end, GroupedDocs).
+    end, lists:sort(Cmp, GroupedDocs)).
 
 maybe_tag_doc(#doc{id=Id, revs={Pos,[_Rev|PrevRevs]}, meta=Meta0}=Doc) ->
     case lists:keymember(ref, 1, Meta0) of
@@ -370,7 +375,7 @@ collect_updates(GroupedDocsAcc, ClientsAcc, MergeConflicts, FullCommit)
->
         % updaters than deal with their possible conflicts, and local docs
         % writes are relatively rare. Can be optmized later if really needed.
         {update_docs, Client, GroupedDocs, [], MergeConflicts, FullCommit2} ->
-            GroupedDocs2 = maybe_tag_grouped_docs(Client, GroupedDocs),
+            GroupedDocs2 = sort_and_tag_grouped_docs(Client, GroupedDocs),
             GroupedDocsAcc2 =
                 merge_updates(GroupedDocsAcc, GroupedDocs2),
             collect_updates(GroupedDocsAcc2, [Client | ClientsAcc],


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