Copy array to another array in same collection

Question

I want to copy items from admin to newAdmins if it does not exist in the newAdmins

Before:

[
  {
    _id: "60801199bf57265ed8b786bc",
    admins: [
     "Kenny"
     "Abu"
     "Raj"
    ],
    newAdmins: [
     "Kenny"
     "Abu"
    ]
  }
]

After:

[
  {
    _id: "60801199bf57265ed8b786bc",
    admins: [
     "Kenny"
     "Abu"
     "Raj"
    ],
    newAdmins: [
     "Kenny"
     "Abu"
     "Raj"
    ]
  }
]

Searched online but could not find a simpler way to do it.

nimrod serok · Accepted Answer · 2022-11-30 09:58:43Z

1

One option is:

db.collection.update({},
[
  {
    $set: {
      newAdmins: {
        $setUnion: [
          "$newAdmins",
          "$admins"
        ]
      }
    }
  }
], 
{multi: true})

See how it works on the playground example

edited Nov 30, 2022 at 9:58

answered Nov 30, 2022 at 9:50

nimrod serok

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4 Comments

hades Over a year ago

i run it says fail to run update: update document must contain key beginning with '$'

nimrod serok Over a year ago

Is it working for you on the playground example? Did you copy the $set part?

hades Over a year ago

playground not working, ya it has the $set part, i just click on the playground example link and click run

nimrod serok Over a year ago

You are right. It was my bad. Updated it now

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