[GitHub] [couchdb] iilyak commented on pull request #3530: Improve retry handling in _all_dbs, _dbs_info and _deleted_dbs

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iilyak commented on pull request #3530:
URL: https://github.com/apache/couchdb/pull/3530#issuecomment-827761831


   I could be wrong, however after reading the code I came to conclusion that in case of a re-try we would be calling `UserCallback({row, Row}, Acc)` multiple times for the same row. This means that the response would have duplicates. Because we don't do anything with rows other than calling [`{ok, Resp1} = chttpd:send_delayed_chunk(Resp0, [Prepend, ?JSON_ENCODE(DbName)]),`](https://github.com/apache/couchdb/blob/main/src/chttpd/src/chttpd_misc.erl#L142
   
   I agree that this PR should fix multiple '[' characters on the fist line. However we still have changed/broken semantics of `_all_dbs` endpoint.
   
   Having in mind recent discussions about introducing limits on each response. It could be a good time to get away from streaming API and instead de-duplicate rows in memory before sending the result to client.
   
   This would fix the long due problem when client receives invalid JSON when erlang process dies while streaming.
   


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