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我有包含 3 组文档项目、用户、评论的 couchDB 数据库 在项目和用户的评论文档中维护多对多关系

用户

{"type":"user","user_id":"U1"},
{"type":"user","user_id":"U2"},
{"type":"user","user_id":"U3"}

物品

{"type":"item","item_id":"I1"},
{"type":"item","item_id":"I2"},
{"type":"item","item_id":"I3"},
{"type":"item","item_id":"I4"}

审查

{"type":"review","item_id":"I1","user_id":"U1","score":4},
{"type":"review","item_id":"I1","user_id":"U2","score":3},
{"type":"review","item_id":"I2","user_id":"U1","score":4},
{"type":"review","item_id":"I3","user_id":"U3","score":1}

我想使用评论获得项目和用户的外部联接，以获得以下结果

预期结果

{"total_rows":16,"offset":0,"rows":[
{"id":"...","key":"I1","value":["item"]},
{"id":"...","key":"I1","value":["review","U1",4]},
{"id":"...","key":"I1","value":["review","U2",3]},
{"id":"...","key":"I1","value":["review","U3",0]},
{"id":"...","key":"I2","value":["item"]},
{"id":"...","key":"I2","value":["review","U1",4]},
{"id":"...","key":"I2","value":["review","U2",0]},
{"id":"...","key":"I2","value":["review","U3",0]},
{"id":"...","key":"I3","value":["item"]},
{"id":"...","key":"I3","value":["review","U1",0]},
{"id":"...","key":"I3","value":["review","U2",0]},
{"id":"...","key":"I3","value":["review","U3",1]},
{"id":"...","key":"I4","value":["item"]},
{"id":"...","key":"I4","value":["review","U1",0]},
{"id":"...","key":"I4","value":["review","U2",0]},
{"id":"...","key":"I4","value":["review","U3",0]}
]}

我正在使用这里提到的技巧 http://wiki.apache.org/couchdb/EntityRelationship#Many_to_Many:_Relationship_documents

"many_join_review": {
           "map": "function(doc) { 
                   if (doc.type == 'review') { 
                        emit(doc.item_id,[doc.type,doc.user_id,doc.score]); 
                    } else if (doc.type == 'item') { 
                        emit(doc.item_id,[doc.type]); 
                    }"
  }

我得到了以下结果

{"total_rows":8,"offset":0,"rows":[
{"id":"d5e26b9da1683232d1c208241a0056fc","key":"I1","value":["item"]},
{"id":"d5e26b9da1683232d1c208241a006bc8","key":"I1","value":["review","U1",4]},
{"id":"d5e26b9da1683232d1c208241a006be0","key":"I1","value":["review","U2",3]},
{"id":"d5e26b9da1683232d1c208241a005eb0","key":"I2","value":["item"]},
{"id":"d5e26b9da1683232d1c208241a0075cf","key":"I2","value":["review","U1",4]},
{"id":"d5e26b9da1683232d1c208241a006409","key":"I3","value":["item"]},
{"id":"d5e26b9da1683232d1c208241a008313","key":"I3","value":["review","U3",1]},
{"id":"d5e26b9da1683232d1c208241a0065d7","key":"I4","value":["item"]}
]}

那么我应该改变什么来获得预期的结果，例如如何在用户不存在评论的项目上获得 0 作为分数。我需要在reduce部分下添加一些东西吗？

谢谢

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0 回答 0