Delete an element from an array in mongodb

Question

Suppose I have an object in mongoDB:

collection_name: book_info

{_id:"121as", "book_num":"12a", "book_name":"lotr", "info":[ {"borrowerAddress":["NY","Delhi"] }, 
{"borrowerAddress":["SI","Ghana"] } ] }

I want to delete an element "NY" from info.

For this I can do is fetch the object from book_info collection and apply loop and delete when element found inside array and save the data into db.

But I want to do is delete and update at same time without fetching data and looping and updating again.

Also, if direct db manipulation is possible, can anyone suggest me whether fetching data, applying loop and deleting data is efficient or deleting data from db directly is more faster, based on solutions provided.

If anyone needs any further information, please let me know.

Additional Question:

doc1: {_id:"121as", "book_num":"12a", "book_name":"lotr", "info":[ {"borrowerAddress":["NY","Delhi"] }, 
{"borrowerAddress":["SI","Ghana"] } ] }

doc2: {_id:"213s", "book_num":"1c", "book_name":"hp", "info":[ {"borrowerAddress":["NY","Delhi"] }, 
{"borrowerAddress":["SI","Ghana"] } ] }

Assume I have multiple documents inside a book_info collection with different book names and details and I want to delete document for "book_name":"lotr" only, I delete address "NY" from document.

turivishal · Accepted Answer · 2021-04-27 08:33:28Z

3

You can try update query with $pull operator to remove matching element from array, $[] positional for all elements in info array,

db.collection.update(
  { "info.borrowerAddress": "NY" },
  { $pull: { "info.$[].borrowerAddress": "NY" },
  { multi: true }
})

Playground

Assume I have multiple documents inside a book_info collection with different book names and details and I want to delete document for "book_name":"lotr" only, I delete address "NY" from document.

db.collection.update(
  { "book_name":"lotr", "info.borrowerAddress": "NY" },
  { $pull: { "info.$[].borrowerAddress": "NY" },
  { multi: true }
})

Playground

edited Apr 27, 2021 at 8:33

answered Apr 27, 2021 at 7:28

turivishal

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6 Comments

Siva Pradhan Over a year ago

Thank you so much for your help. But I'm unable to understand what is going on. Could you please tell me, what exactly is happening?

Siva Pradhan Over a year ago

Can I ask question related to this? Or should I create new question?

turivishal Over a year ago

yes you can ask here if its related to this question.

Siva Pradhan Over a year ago

I have edited my original question, and added additional question. Could you please have a look? In case need any additional information please let me know.

turivishal Over a year ago

I want to fetch document "book_name":"lotr" only, I want to delete address "NY" exactly not getting this, do you want to select data or remove elements?

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