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  1. CouchDB
  2. COUCHDB-1256

Incremental requests to _changes can skip revisions

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 0.10, 0.10.1, 0.10.2, 0.11.1, 0.11.2, 1.0, 1.0.1, 1.0.2, 1.0.3, 1.1
    • Fix Version/s: 1.1.1, 1.2, 1.2.1
    • Component/s: Replication
    • Labels:
      None
    • Environment:

      confirmed on Apache CouchDB 1.1.0, bug appears to be present in 1.0.3 and trunk

    • Skill Level:
      Committers Level (Medium to Hard)

      Description

      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}

        .

        Attachments

        1. jira-1256-test.diff
          1 kB
          Bob Dionne

          Activity

            People

            • Assignee:
              kocolosk Adam Kocoloski
              Reporter:
              kocolosk Adam Kocoloski
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              Dates

              • Created:
                Updated:
                Resolved: