MongoDB - JSON parsing

Question

I have a valid JSON structure in MongoDB that needs to be changed on run time. Here is a valid snapshot of 3 such separate documents in a single collection: -

{
    company : "ABC",
    tags : ["ADMIN", "QA"],
    year : 2010,
    Project : [{
            Domain : "Telecom",
            tags : ["DEV", "ADMIN"],
            size : 15
        }, {
            Domain : "Retail",
            tags : ["ADMIN", "DEV"],
            size : 35
        }, {
            Domain : "Finance",
            tags : ["ADMIN"],
            size : 25
        }
    ]
}
{
    company : "ABC",
    tags : ["QA"],
    year : 2011,
    Project : [{
            Domain : "Telecom",
            tags : ["DEV"],
            size : 15
        }, {
            Domain : "Retail",
            tags : ["ADMIN", "DEV"],
            size : 35
        }, {
            Domain : "Finance",
            tags : ["ADMIN"],
            size : 25
        }
    ]
}
{
    company : "ABC",
    tags : ["QA"],
    year : 2012,
    Project : [{
            Domain : "Telecom",
            tags : ["DEV", "ADMIN"],
            size : 15
        }, {
            Domain : "Retail",
            tags : ["ADMIN", "DEV"],
            size : 35
        }, {
            Domain : "Finance",
            tags : ["ADMIN"],
            size : 25
        }
    ]
}

The structure needs to merge these 3 documents into 1 and then displayed in the following manner: -

{
    "company" : "ABC",
    "tags" : ["ADMIN", "QA"],
    "period" : {
        [{
                year : 2010,
                Project : [{
                        Domain : "Telecom",
                        tags : ["DEV", "ADMIN"],
                        size : 15
                    }, {
                        Domain : "Retail",
                        tags : ["ADMIN", "DEV"],
                        size : 35
                    }, {
                        Domain : "Finance",
                        tags : ["ADMIN"],
                        size : 25
                    }
                ]
            }
        ],
        [{
                year : 2011,
                Project : [{
                        Domain : "Telecom",
                        tags : ["DEV"],
                        size : 15
                    }, {
                        Domain : "Retail",
                        tags : ["ADMIN", "DEV"],
                        size : 35
                    }, {
                        Domain : "Finance",
                        tags : ["ADMIN"],
                        size : 25
                    }
                ]
            }
        ],
        [{
                year : 2012,
                Project : [{
                        Domain : "Telecom",
                        tags : ["DEV", "ADMIN"],
                        size : 15
                    }, {
                        Domain : "Retail",
                        tags : ["ADMIN", "DEV"],
                        size : 35
                    }, {
                        Domain : "Finance",
                        tags : ["ADMIN"],
                        size : 25
                    }
                ]
            }
        ]
    }
}

I know I can use map reduce and get this done. But I thought I should try writing a Java script function for this which could then be called whenever this needed to be done.

Assuming that the following function can be invoked using the collection , a recordset would be passed to the function below.

`var curlprojects = function()
{
    var arrSyn = new Array();
    var JSONString = "";
    var doc;
    var parent;
    var arrTop = new Array();
    while (myCursor.hasNext()) 
    {
        doc = myCursor.next();
        parent = doc.companyName;
        var fulltext = "{\"year\":" + tojson(doc.year) + ",\"project\":" + tojson(doc.project) + "}";
        JSONString = JSONString + fulltext;
    };
    arrSyn.push(JSONString);
    var outext = "{\"period\":" + JSONString + "}";
    print(outext);
}   `

Here's the problem. Eventhough the text appears to be JSON like when I generate it or print it out, it does not print to the screen.

The last line print(outext) displays some weird message asking whether I wish to display 181 preferences, and if I say yes - it lists all reserved words in java script !!!

Any suggestions would be appreciated.

kevinadi · Accepted Answer · 2016-01-22 04:54:05Z

2

As an alternative to using MapReduce or Javascript, you might want to consider using the aggregation framework instead.

The output you wanted could be generated in the Mongo shell using:

db.test.aggregate([

  //optional: match a single company
  {$match:{"company":"ABC"}},

  //expand the "tags" array
  {$unwind:"$tags"},

  //"group by" stage:
  {$group: {

    //group by company
    _id:"$company",

    //add unique tags into the "tags" array
    tags: {$addToSet:"$tags"},

    //add the "Project" details into the "period" array
    period: {$push: {year:"$year", Project:"$Project"}}
  }}
])

answered Jan 22, 2016 at 4:54

kevinadi

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