Incremental requests to _changes can skip revisions
---------------------------------------------------
Key: COUCHDB-1256
URL: https://issues.apache.org/jira/browse/COUCHDB-1256
Project: CouchDB
Issue Type: Bug
Components: Replication
Environment: confirmed on Apache CouchDB 1.1.0, bug appears to be
present in 1.0.3 and trunk
Reporter: Adam Kocoloski
Assignee: Adam Kocoloski
Priority: Blocker
Fix For: 1.0.4, 1.1.1, 1.2
Requests to _changes with style=all_docs&since=N (requests made by the
replicator) are liable to suppress revisions of a document. The following
sequence of curl commands demonstrates the bug:
curl -X PUT localhost:5985/revseq
{"ok":true}
curl -X PUT -Hcontent-type:application/json localhost:5985/revseq/foo -d
'{"a":123}'
{"ok":true,"id":"foo","rev":"1-0dc33db52a43872b6f3371cef7de0277"}
curl -X PUT -Hcontent-type:application/json localhost:5985/revseq/bar -d
'{"a":456}'
{"ok":true,"id":"bar","rev":"1-cc609831f0ca66e8cd3d4c1e0d98108a"}
% stick a conflict revision in foo
curl -X PUT -Hcontent-type:application/json
localhost:5985/revseq/foo?new_edits=false -d
'{"_rev":"1-cc609831f0ca66e8cd3d4c1e0d98108a", "a":123}'
{"ok":true,"id":"foo","rev":"1-cc609831f0ca66e8cd3d4c1e0d98108a"}
% request without since= gives the expected result
curl -Hcontent-type:application/json
localhost:5985/revseq/_changes?style=all_docs
{"results":[
{"seq":2,"id":"bar","changes":[{"rev":"1-cc609831f0ca66e8cd3d4c1e0d98108a"}]},
{"seq":3,"id":"foo","changes":[{"rev":"1-cc609831f0ca66e8cd3d4c1e0d98108a"},{"rev":"1-0dc33db52a43872b6f3371cef7de0277"}]}
],
"last_seq":3}
% request starting from since=2 suppresses revision
1-0dc33db52a43872b6f3371cef7de0277 of foo
macbook:~ (master) $ curl localhost:5985/revseq/_changes?style=all_docs\&since=2
{"results":[
{"seq":3,"id":"foo","changes":[{"rev":"1-cc609831f0ca66e8cd3d4c1e0d98108a"}]}
],
"last_seq":3}
I believe the fix is something like this (though we could refactor further
because Style is unused):
diff --git a/src/couchdb/couch_db.erl b/src/couchdb/couch_db.erl
index e8705be..65aeca3 100644
--- a/src/couchdb/couch_db.erl
+++ b/src/couchdb/couch_db.erl
@@ -1029,19 +1029,7 @@ changes_since(Db, Style, StartSeq, Fun, Acc) ->
changes_since(Db, Style, StartSeq, Fun, [], Acc).
changes_since(Db, Style, StartSeq, Fun, Options, Acc) ->
- Wrapper = fun(DocInfo, _Offset, Acc2) ->
- #doc_info{revs=Revs} = DocInfo,
- DocInfo2 =
- case Style of
- main_only ->
- DocInfo;
- all_docs ->
- % remove revs before the seq
- DocInfo#doc_info{revs=[RevInfo ||
- #rev_info{seq=RevSeq}=RevInfo <- Revs, StartSeq < RevSeq]}
- end,
- Fun(DocInfo2, Acc2)
- end,
+ Wrapper = fun(DocInfo, _Offset, Acc2) -> Fun(DocInfo, Acc2) end,
{ok, _LastReduction, AccOut} = couch_btree:fold(by_seq_btree(Db),
Wrapper, Acc, [{start_key, StartSeq + 1}] ++ Options),
{ok, AccOut}.
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