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From kocol...@apache.org
Subject [5/6] couchdb commit: updated refs/heads/1.x.x to dc00bd8
Date Sat, 18 Jul 2015 15:47:11 GMT
Ensure doc groups are sorted before merging them

We had been implicitly 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/repo
Commit: http://git-wip-us.apache.org/repos/asf/couchdb/commit/50ada24b
Tree: http://git-wip-us.apache.org/repos/asf/couchdb/tree/50ada24b
Diff: http://git-wip-us.apache.org/repos/asf/couchdb/diff/50ada24b

Branch: refs/heads/1.x.x
Commit: 50ada24b120c274b7d959ffe8e780055816b662e
Parents: 5b1b3e1
Author: Adam Kocoloski <adam@cloudant.com>
Authored: Fri Jul 17 19:20:36 2015 -0400
Committer: Adam Kocoloski <adam@cloudant.com>
Committed: Sat Jul 18 11:44:53 2015 -0400

----------------------------------------------------------------------
 src/couchdb/couch_db_updater.erl | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/couchdb/blob/50ada24b/src/couchdb/couch_db_updater.erl
----------------------------------------------------------------------
diff --git a/src/couchdb/couch_db_updater.erl b/src/couchdb/couch_db_updater.erl
index 947669c..c92097f 100644
--- a/src/couchdb/couch_db_updater.erl
+++ b/src/couchdb/couch_db_updater.erl
@@ -222,7 +222,7 @@ handle_cast(Msg, #db{name = Name} = Db) ->
 
 handle_info({update_docs, Client, GroupedDocs, NonRepDocs, MergeConflicts,
         FullCommit}, Db) ->
-    GroupedDocs2 = [[{Client, D} || D <- DocGroup] || DocGroup <- GroupedDocs],
+    GroupedDocs2 = sort_and_tag_groups(Client, GroupedDocs),
     if NonRepDocs == [] ->
         {GroupedDocs3, Clients, FullCommit2} = collect_updates(GroupedDocs2,
                 [Client], MergeConflicts, FullCommit);
@@ -291,8 +291,7 @@ 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 = [[{Client, Doc} || Doc <- DocGroup]
-                    || DocGroup <- GroupedDocs],
+            GroupedDocs2 = sort_and_tag_groups(Client, GroupedDocs),
             GroupedDocsAcc2 =
                 merge_updates(GroupedDocsAcc, GroupedDocs2, []),
             collect_updates(GroupedDocsAcc2, [Client | ClientsAcc],
@@ -302,6 +301,15 @@ collect_updates(GroupedDocsAcc, ClientsAcc, MergeConflicts, FullCommit)
->
     end.
 
 
+sort_and_tag_groups(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,
+    SortedGroups = lists:sort(Cmp, GroupedDocs),
+    [[{Client, D} || D <- DocGroup] || DocGroup <- SortedGroups].
+
 btree_by_seq_split(#doc_info{id=Id, high_seq=KeySeq, revs=Revs}) ->
     {RevInfos, DeletedRevInfos} = lists:foldl(
         fun(#rev_info{deleted = false, seq = Seq} = Ri, {Acc, AccDel}) ->


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