Try this
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $push: {"myarray": {
userId:ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}}
)
Explination:
in the first statment $pull
removes the element with userId= ObjectId("570ca5e48dbe673802c2d035")
from the array on the document where _id = ObjectId("57315ba4846dd82425ca2408")
In the second one $push
inserts
this object { userId:ObjectId("570ca5e48dbe673802c2d035"), point: 10 }
in the same array.