[couchdb] branch fix-limit0-for-views created (now d9d2bac)

[va...@apache.org]

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vatamane pushed a change to branch fix-limit0-for-views
in repository https://gitbox.apache.org/repos/asf/couchdb.git.


      at d9d2bac  Fix meta result for views when limit = 0

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     new d9d2bac  Fix meta result for views when limit = 0

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[couchdb] 01/01: Fix meta result for views when limit = 0

[va...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

vatamane pushed a commit to branch fix-limit0-for-views
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit d9d2bacd402921e08db78cc818106836ce3685af
Author: Nick Vatamaniuc <va...@gmail.com>
AuthorDate: Wed Sep 15 15:31:34 2021 -0400

    Fix meta result for views when limit = 0
    
    Previously, as soon as one row returned, we immediately stopped, erroneously
    assuming that meta for all ranges have already been received. However, it was
    possible that we'd get meta from range 00-7f, then a row from 00-7f before
    getting meta from 7f-ff and thus we'd return an empty result.
    
    To fix the issue we simply re-use the already existing limit=0 clause from the
    fabric_view:maybe_send_row/1 function which will wait until there is a complete
    ring before returning. That relies on updating the counters (the ring) only
    with meta return and not with view rows, so if the ring is complete, we know we
    only completed with meta.
    
    The other issue with limit=0 clause was that it wasn't properly ack-ing the
    received row. Rows are acked for sorted=false case below and for the regular
    limit>0, sorted=true case in fabric_view:get_next_row/1.
    
    Issue: https://github.com/apache/couchdb/issues/3750
---
 src/fabric/src/fabric_view_map.erl | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/fabric/src/fabric_view_map.erl b/src/fabric/src/fabric_view_map.erl
index b8d0d39..6477654 100644
--- a/src/fabric/src/fabric_view_map.erl
+++ b/src/fabric/src/fabric_view_map.erl
@@ -146,10 +146,11 @@ handle_message({meta, Meta0}, {Worker, From}, State) ->
         }}
     end;
 
-handle_message(#view_row{}, {_, _}, #collector{limit=0} = State) ->
-    #collector{callback=Callback} = State,
-    {_, Acc} = Callback(complete, State#collector.user_acc),
-    {stop, State#collector{user_acc=Acc}};
+handle_message(#view_row{}, {_, From}, #collector{limit=0} = State) ->
+    rexi:stream_ack(From),
+    % Rely on limit=0 clause in maybe_send_row/1 to wait until all
+    % shard ranges reply with meta
+    fabric_view:maybe_send_row(State);
 
 handle_message(#view_row{} = Row, {_,From}, #collector{sorted=false} = St) ->
     #collector{callback=Callback, user_acc=AccIn, limit=Limit} = St,