How do I update MongoDB document fields only if they don't exist?

Question

I have collection foo with documents like:

{site_id: \'xxx\', title: {ru: \'a\', en: \'b\'}, content:         


        

Answer 1

there is a update field operator $setOnInsert which meets your requirement. Please read the documents here: https://docs.mongodb.com/manual/reference/operator/update/setOnInsert/#up._S_setOnInsert