$bit(bitwise update)

The $bit operator is used to perform bitwise operations on integer values. It can be used to update integer fields in documents by applying bitwise AND, OR, and XOR operations. Bitwise operators like $bit aren't designed for incrementing values, but for manipulating bits directly (like checking, setting, or clearing specific bits).

{ $bit: { <field>: { <operator>: <number> } } }

Let's understand the usage with the following sample json.

{
  "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
   "name": "Lakeshore Retail | DJ Equipment Stop - Port Cecile",
  "location": {
    "lat": 60.1441,
    "lon": -141.5012
  },
  "staff": {
    "totalStaff": {
      "fullTime": 2,
      "partTime": 0
    }
  },
  "sales": {
    "salesByCategory": [
      {
        "categoryName": "DJ Headphones",
        "totalSales": 35921
      }
    ],
    "fullSales": 3700
  },
  "promotionEvents": [
    {
      "eventName": "Bargain Blitz Days",
      "promotionalDates": {
        "startDate": {
          "Year": 2024,
          "Month": 3,
          "Day": 11
        },
        "endDate": {
          "Year": 2024,
          "Month": 2,
          "Day": 18
        }
      },
      "discounts": [
        {
          "categoryName": "DJ Turntables",
          "discountPercentage": 18
        },
        {
          "categoryName": "DJ Mixers",
          "discountPercentage": 15
        }
      ]
    }
  ],
  "tag": [
    "#ShopLocal",
    "#SeasonalSale",
    "#FreeShipping",
    "#MembershipDeals"
  ]
}

db.stores.updateOne(
  { "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5" },
  { $bit: { "staff.totalStaff.partTime": { and: 1 } } }
)

This query would return the following document. The AND of 0 and 1 is 0 hence the new value of the field is 0.

{
  "acknowledged": true,
  "insertedId": null,
  "matchedCount": "1",
  "modifiedCount": "1",
  "upsertedCount": 0
}

db.stores.updateOne(
  { "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5" },
  { $bit: { "staff.totalStaff.partTime": { "or" : 1 } } }
)

This query would return the following document. The OR of 0 and 1 is 1 hence the new value of the field is 1.

{
  "acknowledged": true,
  "insertedId": null,
  "matchedCount": "1",
  "modifiedCount": "1",
  "upsertedCount": 0
}

db.stores.updateOne(
  { "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5" },
  { $bit: { "staff.totalStaff.partTime": { "xor" : 1 } } }
)

This query would return the following document. The XOR of 1 and 1 is 0 hence the new value of the field is 0.

{
  "acknowledged": true,
  "insertedId": null,
  "matchedCount": "1",
  "modifiedCount": "1",
  "upsertedCount": 0
}

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