MongoDB sort map elements when searching a particular document

Question

I have a query that returns a single document but have a map field. I would like to sort the map elements, is this possible?

The data is something like this:

Calendars:

{
    "_id" : "1f5c0468-3249-4eee-ae65-79fc134f37c7",
    "countryId" : "60a562ba-43d1-48b3-bd07-7aebbb2c0123",
    "name" : "Bangladesh Holiday 2019",
    "year" : 2019,
    "holidays" : {
        "2019-02-21" : "Language Martyrs' Day",
        "2019-03-17" : "Sheikh Mujibur Rahman's birthday",
        "2019-03-26" : "Independence Day",
        "2019-04-14" : "Bengali New Year",
        "2019-04-21" : "Shab e-Barat",
        "2019-05-01" : "May Day",
        "2019-05-19" : "Buddha Purnima",
        "2019-05-31" : "Jumatul Bidah",
        "2019-06-01" : "Night of Destiny",
        "2019-06-02" : "Night of Destiny",
        "2019-06-03" : "Compensate leave for Night of Destiny",
        "2019-06-04" : "Eid al-Fitr",
        "2019-06-05" : "Eid ul-Fitr",
        "2019-06-06" : "Eid ul-Ftr Holiday",
        "2019-08-09" : "Compensate leave for Eid ul-Adha",
        "2019-08-11" : "Eid ul-Adha Day 1",
        "2019-08-12" : "Eid ul-Adha Day 2",
        "2019-08-13" : "Eid ul-Adha Day 3",
        "2019-08-15" : "National Mourning Day",
        "2019-08-23" : "Janmashtami",
        "2019-09-10" : "Ashura",
        "2019-10-08" : "Durga Puja",
        "2019-11-10" : "Eid e-Milad-un Nabi",
        "2019-12-16" : "Victory Day",
        "2019-12-25" : "Christmas Day"
    }
}

The simple query to get a particular document is like this:

db.getCollection('calendars').find({ "_id" : "1f5c0468-3249-4eee-ae65-79fc134f37c7" })

Now, is it possible to sort the map of holidays by date?

store result in java script veritable and do sorting . take help from https://stackoverflow.com/questions/5467129/sort-javascript-object-by-key — sandeep rawat, Aug 08 '19 at 09:14
you can use `objectToArray` to then unwind your data, sort it and group it together via the aggregation framework if you are on the right version See for example: https://docs.mongodb.com/manual/reference/operator/aggregation/objectToArray/ — pandaadb, Aug 08 '19 at 09:52

Hardik Shah · Accepted Answer · 2019-08-08T10:43:06.887

Based on your sample JSON: (As far as I understood)

Date is key (We must have some mechanism to convert the key to value)
Date is a string (We must have to convert String date to Date object)
Then sort on date
Wrap up whole structure again same as sample JSON but should be sorted

Below is the result of using aggregation:

db.Collection.aggregate([
    { $match: { "_id" : "1f5c0468-3249-4eee-ae65-79fc134f37c7" }}, // Let's fetch particular document
    { $project: {
        countryId: 1,
        name: 1,
        year: 1,
        holidays: { $objectToArray: "$holidays" }, // Let's convert Object to Array first
    }},
    { $unwind: "$holidays" }, // Let's unwind So we can easily convert String date to Date object
    { $addFields: {
      convertedDate: { $toDate: "$holidays.k" } // Let's convert string date to date object
    }},
    { $sort: { "convertedDate": -1 }}, // let's sort converted date (-1 or 1)
    { $group: {  // Let's wrap up whole unwinded object to single
      _id: "$_id",
      countryId: {$first: "$countryId"},
      name: {$first: "$name"},
      year: {$first: "$year"},
      holidays: {$push: "$holidays"} 
    }},
    { $project: { // Let's convert holiday to object again but this time it would be sorted
        countryId: 1,
        name: 1,
        year: 1,
        holidays: { $arrayToObject: "$holidays" }
    }}
])

Output:

{
    "_id" : ObjectId("5d4be8738ac090b7119314a3"),
    "countryId" : "60a562ba-43d1-48b3-bd07-7aebbb2c0123",
    "name" : "Bangladesh Holiday 2019",
    "year" : 2019,
    "holidays" : {
        "2019-12-25" : "Christmas Day",
        "2019-12-16" : "Victory Day",
        "2019-11-10" : "Eid e-Milad-un Nabi",
        "2019-10-08" : "Durga Puja",
        "2019-09-10" : "Ashura",
        "2019-08-23" : "Janmashtami",
        "2019-08-15" : "National Mourning Day",
        "2019-08-13" : "Eid ul-Adha Day 3",
        "2019-08-12" : "Eid ul-Adha Day 2",
        "2019-08-11" : "Eid ul-Adha Day 1",
        "2019-08-09" : "Compensate leave for Eid ul-Adha",
        "2019-06-06" : "Eid ul-Ftr Holiday",
        "2019-06-05" : "Eid ul-Fitr",
        "2019-06-04" : "Eid al-Fitr",
        "2019-06-03" : "Compensate leave for Night of Destiny",
        "2019-06-02" : "Night of Destiny",
        "2019-06-01" : "Night of Destiny",
        "2019-05-31" : "Jumatul Bidah",
        "2019-05-19" : "Buddha Purnima",
        "2019-05-01" : "May Day",
        "2019-04-21" : "Shab e-Barat",
        "2019-04-14" : "Bengali New Year",
        "2019-03-26" : "Independence Day",
        "2019-03-17" : "Sheikh Mujibur Rahman's birthday",
        "2019-02-21" : "Language Martyrs' Day"
    }
}

the comments really is a big help also, thanks a lot – Borgy Manotoy Aug 08 '19 at 11:09 — Borgy Manotoy, Aug 08 '19 at 11:09

MongoDB sort map elements when searching a particular document

1 Answers1