Mongodb update nested array by id - mongodb

Question

I have the following document and want to update state
Document ID: ObjectId("5a4e5a448b70d50e34d204a5")
Target ID: ObjectId("5a4e5a438b70d50e34d203ea")
I have no idea how to update the state to e.g. 4
{
"_id" : ObjectId("5a4e5a448b70d50e34d204a5"),
"name" : "Wirtschaftsdienst",
"date" : ISODate("2012-10-07T00:00:00.000Z"),
"comment" : null,
"tasks" : [
{
"name" : "Speisen und Getränke",
"sections" : [
{
"start" : 46800,
"end" : 72000,
"entirely" : true,
"assistants" : [
{
"assistant" : {
"_id" : ObjectId("5a4e5a438b70d50e34d203ea")
},
"state" : 3
},
{
"assistant" : {
"_id" : ObjectId("5a4e5a438b70d50e34d203f4")
},
"state" : 3
}
]
}
]
}
]
}

Answer 1

Use positional operator $[] along with arrayFilters to get your job done!
Try this query:
db.collection.update(
{"_id" : ObjectId("5a4e5a448b70d50e34d204a5")},
{$set: {"tasks.$[].sections.$[].assistants.$[element].state":4}},
{arrayFilters: [ {"element.assistant":{"_id" :
ObjectId("5a4e5a438b70d50e34d203ea")} }
], multi:true}
)
And the output is:
/* 1 */
{
"_id" : ObjectId("5a4e5a448b70d50e34d204a5"),
"name" : "Wirtschaftsdienst",
"date" : ISODate("2012-10-07T00:00:00.000Z"),
"comment" : null,
"tasks" : [
{
"name" : "Speisen und Getränke",
"sections" : [
{
"start" : 46800,
"end" : 72000,
"entirely" : true,
"assistants" : [
{
"assistant" : {
"_id" : ObjectId("5a4e5a438b70d50e34d203ea")
},
"state" : 4.0
},
{
"assistant" : {
"_id" : ObjectId("5a4e5a438b70d50e34d203f4")
},
"state" : 3.0
}
]
}
]
}
]
}