Question

以下是我的收藏“fullclicklogs”，其中包含许多json文档：

{
            "_id" : ObjectId("58fe78dcfbe21fa7896552e8"),
            "preview" : false,
            "offset" : 0,
            "result" : {
                    "tab_name" : "People-Tab",
                    "page_name" : "PEOPLE",
                    "result_number" : "1",
                    "page_num" : "0",

            }
    }
{
             "_id" : ObjectId("58fe78dcfbe21fa7896552e9"),
            "preview" : false,
            "offset" : 0,
            "result" : {
                    "tab_name" : "People-Tab",
                    "page_name" : "PEOPLE",
                    "result_number" : "5",
                    "page_num" : "0",
}
}

我想在我的新收藏集“doc_rank”中添加一个新字段“DOCRANK”DOCRANK = page_num*25+result_number

更新：由于page_num和result_number是字符串，我使用以下命令将它们转换为int：

 >db.fullclicklogs.find().forEach( function (x) {
    x.result.page_num = parseInt(x.result.page_num);
    db.fullclicklogs.save(x);
    });

>db.fullclicklogs.find().forEach( function (x) {
x.result.result_number = parseInt(x.result.result_number);
db.fullclicklogs.save(x);
});

错误：

2017-04-25T11:50:54.830-0700 E QUERY    [thread1] TypeError: x.result is undefined :
@(shell):2:1
DBQuery.prototype.forEach@src/mongo/shell/query.js:501:1
@(shell):1:1
>

下面是我用来获取DOCRANK的聚合，但我的结果集合中仍然获得值null：

db.getCollection('fullclicklogs').aggregate( [
   {
      $project: {
         DOCRANK: {
            $let: {
               vars: {
                  total: { $multiply: [ "$result.page_num", 25 ] },
               },
               in: { $add: [ "$$total", "$result.result_number" ] }
            }
         }
      }
   },
   {
   $out: "doc_rank1"
   }
] )

更新：使用点表示法来修复我的代码。但现在我得到“$ multiply只支持数字类型，而不是字符串”

汇总输出：

assert: command failed: {
        "ok" : 0,
        "errmsg" : "$multiply only supports numeric types, not string",
        "code" : 16555,
        "codeName" : "Location16555"
} : aggregate failed
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:16:14
assert.commandWorked@src/mongo/shell/assert.js:370:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1319:5
@(shell):1:1

2017-04-25T11:12:11.420-0700 E QUERY    [thread1] Error: command failed: {
        "ok" : 0,
        "errmsg" : "$multiply only supports numeric types, not string",
        "code" : 16555,
        "codeName" : "Location16555"
} : aggregate failed :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:16:14
assert.commandWorked@src/mongo/shell/assert.js:370:5
DBCollection.prototype.aggregate@src/mongo/shell/collection.js:1319:5
@(shell):1:1

我可以知道我的代码有什么问题吗？任何帮助表示赞赏。感谢

Answer 1

您需要使用点表示法来访问嵌入字段。 result是嵌入式文档，result_number和page_num是嵌入式字段。

尝试

db.getCollection('fullclicklogs').aggregate( [
   {
      $project: {
         DOCRANK: {
            $let: {
               vars: {
                  total: { $multiply: [ "$result.page_num", 25 ] },
               },
               in: { $add: [ "$$total", "$result.result_number" ] }
            }
         }
      }
   },
   {
   $out: "doc_rank1"
   }
] )

更多https://docs.mongodb.com/manual/core/document/#document-dot-notation

Mongodb：如何使用$乘以数字？

1 个答案: