CODEWITHSUNDEEP
mongodbshelldatabase
user3332859
user3332859

Reputation: 13

How to change type of a field in mongo db collection

I inserted some data in a database collection named Orders. And I have a field named numberofh.

But all fields in my collection are string types. I am connected to the mongo db shell on the server and I want to delete all orders where numberofh is less then 5.

db.orders.remove({numberofh:{$lt:20}}) does not work because numberofh is a string so $lt won't work.

Can I do this some other way such as sdb.orders.remove({parseInt(numberofh}:{$lt:20})?

Upvotes: 1

Views: 437

Answers (2)

heinob
heinob

Reputation: 19474

You cannot compare strings with numbers in mongoDB. You have to first insert a new field, that is a numerical representation of numberofh. And you have to do the conversion client-side. There is no possibility, to create a field in dependency of the value of another field. 

db.orders.find( {} ).forEach( function (x) {   
    x.numberofh_n = parseInt( x.numberofh, 10 ); 
    db.orders.save( x );
});

After that you can remove the records by the new field:

db.orders.remove( { numberofh_n: { $lt:20 } } )

Upvotes: 1

Lix
Lix

Reputation: 47976

I think you'll need to iterate over each of the documents and convert each value as the cursor reaches it:

db.orders.find().forEach( function( doc ) {  
  // Extract the relevant value and convert to an int
  var numberofh_int = parseInt( doc[ "numberofh" ], 10 );
  // Perform conditionals on the value
  if ( numberofh_int < 20 ){ // $lt:20
    // Remove the document if it answers to the conditions
    db.orders.remove( doc );
  }
} );

Upvotes: 1

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