Mongodb - Mongo DB- Update document field if a particular field has more than one document matches

sabu
January 11, 2024
180 views
0 votes
2 Answers

Scenario

Example Mongo DB documents
Doc 1
{
_id 123
Customer: customer A
State: TX
City: Houston
checksum: 1111
IsBundlled:
}

Doc 2
{
_id 1234
Customer: customer B
State: TX
City: Houston
checksum: 1111
IsBundlled:
}

Doc 3
{
_id 12345
Customer: customer c
State: NY
City: Buffalo
checksum: 2222
IsBundlled:

}

Checksum field is populated in app code using State and City fields.

Problem

Populate IsBundled field for each document to true, if a checksum matches more than 1 documents. In our case 1st and 2nd documents needs to updated with isBundled: true . Instead of adding this logic in application code, I am looking for better solutions using aggregation pipeline

Answers

- R2D2
- January 11, 2024 at 4:05 pm
- 0 votes
0
Maybe something like this:
```
db.collection.aggregate([
{
"$group": {
  "_id": "$checksum",
   "toUpdate": {
    "$addToSet": "$_id"
   },
  cnt: {
    $sum: 1
    }
  }
  },
  {
   $match: {
    cnt: {
      $gt: 1
   }
  }
 },
 {
  $unwind: "$toUpdate"
 }
 ]).toArray().forEach(function(d){ db.collection.update({_id:d.toUpdate},{$set:{ IsBundled:"true" }})   })
```
aggregation playground

Explained:
1. Group on checksum and get document _id per same checksum
2. Filter checksum matching more then one document
3. Unwind toUpdate array with the _id’s needed to be updated
4. Loop over the result to update all the documents with IsBundled: true
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- AniketRaj
- January 11, 2024 at 9:11 pm
- 0 votes
0
MongoDb Playground link : https://mongoplayground.net/p/pV_UbQ-ADby

$group: To group the matching documents.
$set: To modify the document
$gt: To check if greater than condition
$replaceRoot: To replace the current document structure by another.
```
db.collection.aggregate([
  {
    $group: {
      _id: "$checksum",
      count: {
        $sum: 1
      },
      bundles: {
        $push: "$$ROOT"
      }
    }
  },
  {
    "$unwind": "$bundles"
  },
  {
    $set: {
      "bundles.IsBundled": {
        $gt: [
          "$count",
          1
        ]
      }
    }
  },
  {
    "$replaceRoot": {
      "newRoot": "$bundles"
    }
  }
])
```
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