MongoDB - Update objects in a document s array nested updating

Question

Assume we have the following collection  which I have few questions about            id    ObjectId  4faaba123412d654fe83hg876         user id    123456       total    100       items                                         item name     my item one                        price    20                                                   item name     my item two                        price    50                                                   item name     my item three                        price    30                         1 - I want to increase the price for  item name   my item two  and if it doesn t exists  it should be appended to the  items  array   2 - How can I update two fields at the same time  For example  increase the price for  my item three  and at the same time increase the  total   with the same value    I prefer to do this on the MongoDB side  otherwise I have to load the document in client-side  Python  and construct the updated document and replace it with the existing one in MongoDB   UPDATE This is what I have tried and works fine IF THE Object Exists     db test invoice update  user id   123456    items item name   my item one       inc    items   price   10      But if the key doesn t exist it does nothing   Also it only updates the nested object  There is no way with this command to update the  total  field as well

User · Answer

There is no way to do this in single query. You have to search the document in first query:

If document exists:

db.bar.update( {user_id : 123456 , "items.item_name" : "my_item_two" } , 
                {$inc : {"items.$.price" : 1} } , 
                false , 
                true);

Else

db.bar.update( {user_id : 123456 } , 
                {$addToSet : {"items" : {'item_name' : "my_item_two" , 'price' : 1 }} } ,
                false , 
                true);

No need to add condition {$ne : "my_item_two" }.

Also in multithreaded enviourment you have to be careful that only one thread can execute the second (insert case, if document did not found) at a time, otherwise duplicate embed documents will be inserted.

User · Answer

We can use  set operator to update the nested array inside object filed update the value  db getCollection  geolocations   update                 id    ObjectId  5bd3013ac714ea4959f80115             geolocation country     United States of America               set                        geolocation   country     USA                       false     true

User · Answer

For question  1  let s break it into two parts   First  increment any document that has  items item name  equal to  my item two    For this you ll have to use the positional     operator   Something like    db bar update   user id   123456    items item name     my item two                         inc     items   price    1                       false                    true     Note that this will only increment the first matched subdocument in any array  so if you have another document in the array with  item name  equal to  my item two   it won t get incremented    But this might be what you want    The second part is trickier   We can push a new item to an array without a  my item two  as follows    db bar update   user id   123456   items item name      ne    my item two                          addToSet     items      item name     my item two     price    1                        false                    true     For your question  2  the answer is easier  To increment the total and the price of item three in any document that contains  my item three   you can use the  inc operator on multiple fields at the same time  Something like   db bar update    items item name      ne    my item three                        inc    total   1    items   price    1                    false                  true

[mongodb] MongoDB - Update objects in a document's array (nested updating)

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