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From dav...@apache.org
Subject [6/7] couch commit: updated refs/heads/COUCHDB-3287-pluggable-storage-engines to cde5780
Date Wed, 22 Feb 2017 16:11:45 GMT
Ensure deterministic revisions for attachments

This re-fixes a corner case when recreating a document with an
attachment in a single multipart request. Since we don't detect that we
need a new revision until after the document has been serialized we need
to be able to deserialize the body so that we can generate the same
revisions regardless of the contents of the database. If we don't do
this then we end up including information from the position of the
attachment on disk in the revision calculation which can introduce
branches in the revision tree.

I've left this as a separate commit from the pluggable storage engine
work so that its called out clearly for us to revisit.

COUCHDB-3255


Project: http://git-wip-us.apache.org/repos/asf/couchdb-couch/repo
Commit: http://git-wip-us.apache.org/repos/asf/couchdb-couch/commit/cde57808
Tree: http://git-wip-us.apache.org/repos/asf/couchdb-couch/tree/cde57808
Diff: http://git-wip-us.apache.org/repos/asf/couchdb-couch/diff/cde57808

Branch: refs/heads/COUCHDB-3287-pluggable-storage-engines
Commit: cde57808f191b6894b1d599abf978b7ca79123e7
Parents: f3b454e
Author: Paul J. Davis <paul.joseph.davis@gmail.com>
Authored: Wed Feb 8 07:25:37 2017 -0600
Committer: Paul J. Davis <paul.joseph.davis@gmail.com>
Committed: Wed Feb 22 10:11:03 2017 -0600

----------------------------------------------------------------------
 src/couch_bt_engine.erl  | 10 +++++++++-
 src/couch_db.erl         | 12 +-----------
 src/couch_db_updater.erl | 12 +++++++++++-
 3 files changed, 21 insertions(+), 13 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/couchdb-couch/blob/cde57808/src/couch_bt_engine.erl
----------------------------------------------------------------------
diff --git a/src/couch_bt_engine.erl b/src/couch_bt_engine.erl
index 7c0fdbc..ebf312c 100644
--- a/src/couch_bt_engine.erl
+++ b/src/couch_bt_engine.erl
@@ -324,7 +324,15 @@ serialize_doc(#st{} = St, #doc{} = Doc) ->
     SummaryBin = ?term_to_bin({Body, Atts}),
     Md5 = couch_crypto:hash(md5, SummaryBin),
     Data = couch_file:assemble_file_chunk(SummaryBin, Md5),
-    Doc#doc{body = Data}.
+    % TODO: This is a terrible hack to get around the issues
+    %       in COUCHDB-3255. We'll need to come back and figure
+    %       out a better approach to handling the case when we
+    %       need to generate a new revision id after the doc
+    %       has been serialized.
+    Doc#doc{
+        body = Data,
+        meta = [{comp_body, Body} | Doc#doc.meta]
+    }.
 
 
 write_doc_body(St, #doc{} = Doc) ->

http://git-wip-us.apache.org/repos/asf/couchdb-couch/blob/cde57808/src/couch_db.erl
----------------------------------------------------------------------
diff --git a/src/couch_db.erl b/src/couch_db.erl
index cd03b49..51123a9 100644
--- a/src/couch_db.erl
+++ b/src/couch_db.erl
@@ -934,7 +934,7 @@ prep_and_validate_replicated_updates(Db, [Bucket|RestBuckets], [OldInfo|RestOldI
 
 
 
-new_revid(#doc{body=Body0, revs={OldStart,OldRevs}, atts=Atts, deleted=Deleted}) ->
+new_revid(#doc{body=Body, revs={OldStart,OldRevs}, atts=Atts, deleted=Deleted}) ->
     DigestedAtts = lists:foldl(fun(Att, Acc) ->
         [N, T, M] = couch_att:fetch([name, type, md5], Att),
         case M == <<>> of
@@ -942,16 +942,6 @@ new_revid(#doc{body=Body0, revs={OldStart,OldRevs}, atts=Atts, deleted=Deleted})
             false -> [{N, T, M} | Acc]
         end
     end, [], Atts),
-    Body = case Body0 of
-        {summary, [_Len, _Md5, BodyAtts], _SizeInfo, _AttsFd} ->
-            {CompBody, _CompAtts} = binary_to_term(BodyAtts),
-            couch_compress:decompress(CompBody);
-        {summary, [_Len, BodyAtts], _SizeInfo, _AttsFd} ->
-            {CompBody, _CompAtts} = binary_to_term(BodyAtts),
-            couch_compress:decompress(CompBody);
-        Else ->
-            Else
-    end,
     case DigestedAtts of
         Atts2 when length(Atts) =/= length(Atts2) ->
             % We must have old style non-md5 attachments

http://git-wip-us.apache.org/repos/asf/couchdb-couch/blob/cde57808/src/couch_db_updater.erl
----------------------------------------------------------------------
diff --git a/src/couch_db_updater.erl b/src/couch_db_updater.erl
index 71628c6..360a441 100644
--- a/src/couch_db_updater.erl
+++ b/src/couch_db_updater.erl
@@ -520,7 +520,17 @@ merge_rev_tree(OldInfo, NewDoc, Client, Limit, false)
             % Update the new doc based on revisions in OldInfo
             #doc_info{revs=[WinningRev | _]} = couch_doc:to_doc_info(OldInfo),
             #rev_info{rev={OldPos, OldRev}} = WinningRev,
-            NewRevId = couch_db:new_revid(NewDoc#doc{revs={OldPos, [OldRev]}}),
+            Body = case couch_util:get_value(comp_body, NewDoc#doc.meta) of
+                CompBody when is_binary(CompBody) ->
+                    couch_compress:decompress(CompBody);
+                _ ->
+                    NewDoc#doc.body
+            end,
+            RevIdDoc = NewDoc#doc{
+                revs = {OldPos, [OldRev]},
+                body = Body
+            },
+            NewRevId = couch_db:new_revid(RevIdDoc),
             NewDoc2 = NewDoc#doc{revs={OldPos + 1, [NewRevId, OldRev]}},
 
             % Merge our modified new doc into the tree


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