CODEWITHSUNDEEP
mongodb
cavalier
cavalier

Reputation: 101

How to update a field of all documents in mongodb?

I'm trying to do the equivalent of 

UPDATE TABLENAME SET COLUMN = COLUMN * 0.725

in mongodb.

Here is what I tried but doesn't seem to work. Help! 

db.costs.update(
  {$mul: {totalcost: NumberDecimal("0.725")}},
  {multi: true}
);

generates

"errmsg" : "unknown top level operator: $mul"

and the below 

db.costs.update(
  { recordId: {$regex:"*"}},
  {$mul: {totalcost: NumberDecimal("0.725")}},
  {multi: true}
);

generates

"errmsg" : "Regular expression is invalid: nothing to repeat"

Apparently I'm missing the syntax and scoured through the documentation but couldn't find anything that could help.

thanks

Upvotes: 0

Views: 250

Answers (2)

Shyam
Shyam

Reputation: 114

Edited. Looks like you are trying to do a bulk update.

var bulk = db.getCollection('collection-name').initializeUnorderedBulkOp()
bulk.find({}).update({ $mul : {points: 2}}); // will multiply the field by 2
bulk.execute();

There is should work. For more info, check out unordered and ordered operations.

Upvotes: 0

Himanshu Sharma
Himanshu Sharma

Reputation: 3010

The following query can get us the expected output:

db.collection.updateMany({},
{
    $mul:{
        "totalCost": 0.725
    }
})

Data set:

{ "_id" : ObjectId("5d882f0d38db7cf8d3f75cdd"), "totalCost" : 1000 }
{ "_id" : ObjectId("5d882f0d38db7cf8d3f75cde"), "totalCost" : 1200 }
{ "_id" : ObjectId("5d882f0d38db7cf8d3f75cdf"), "totalCost" : 1500 }
{ "_id" : ObjectId("5d882f0d38db7cf8d3f75ce0"), "totalCost" : 1800 }

Output:

{ "_id" : ObjectId("5d882f0d38db7cf8d3f75cdd"), "totalCost" : 725 }
{ "_id" : ObjectId("5d882f0d38db7cf8d3f75cde"), "totalCost" : 870 }
{ "_id" : ObjectId("5d882f0d38db7cf8d3f75cdf"), "totalCost" : 1087.5 }
{ "_id" : ObjectId("5d882f0d38db7cf8d3f75ce0"), "totalCost" : 1305 }

Upvotes: 1

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