How to update document with nested array in mongodb [duplicate] - mongodb

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Mongodb $push in nested array
(4 answers)
Closed 4 years ago.
I've got a document in a collection 'events' with the following structure:
{
"_id" : "abc",
"text" : "some text",
}
I wish to update the document by inserting an array named guestOwner. The result I want would update the document like this:
{
"_id" : "abc",
"text" : "some text",
"guestOwner" : [
{
"name" : "JACK BLACK",
"guests" : [
"GUEST1",
"GUEST2"
]
}
]
}
So I tried an mongo update with the following:
db.events.update({ _id: eventid }, { $push: { guestOwner: { name: username, guests: allGuests } } });
where 'username' is a string, and 'allGuests' is an array of names ["Guest1", "Guest2"]
The issue for me is when a subsequent update to the document occurs, I would want to push a the new 'allGuests' array into the existing one if the name is the same. For example, if a second update occurs with 'allGuests' = ["GUEST3"], and with the same name = "JACK BLACK", I would want the document to be:
{
"_id" : "abc",
"text" : "some text",
"guestOwner" : [
{
"name" : "JACK BLACK",
"guests" : [
"GUEST1",
"GUEST2"
"GUEST3"
]
}
]
}
BUT, if the document were updated with a different name = 'JOHN SMITH' where allGuests array = ["GUEST3"], it would create:
{
"_id" : "abc",
"text" : "some text",
"guestOwner" : [
{
"name" : "JACK BLACK",
"guests" : [
"GUEST1",
"GUEST2"
]
},
{
"name" : "JOHN SMITH",
"guests" : [
"GUEST3"
]
}
]
}
Would I need conditional statements surrounding the mongo update to check for guestOwner[0].name? Not sure if mongo could do this on its own, or if a bunch of logic is going to be necessary.

Answer 1

You could simply do an update where in the query section you would specify the name:
db.events.update({
"_id" : ObjectId("someId"), "guestOwner.name": "JACK BLACK"}, {
$push: { "guestOwner.$.guests": "GUEST11" // etc }
})
If this returns the number of updated elements to be 1 you are good to go since the name exists etc.
If it returns 0 then that name does not exists so you can run:
db.events.update({"_id" : ObjectId("someId")}, {
$addToSet: { guestOwner: { name: "JACK BLACK" // etc }}
})
It would save you one call since if you have to check if the record exists you would always do 2 rounds. One to check and another to take action based on the result. Here if the records is already there you only do one update.