Mongo remove from nested object by value - mongodb

Question

I have a Mongo collection the consists of a document and a nested object describing what collections the document is in and when it was added. I would like to remove key-value pairs from a nested object based on a condition, e.g. is the value (a date) before 1-1-2016.
Example:
{
"_id" : ObjectId("581214940911ad3de98002db"),
"collections" : {
"c01" : ISODate("2016-10-27T15:52:04.512Z"),
"c02" : ISODate("2015-11-21T16:06:06.546Z")
}
}
needs to become
{
"_id" : ObjectId("581214940911ad3de98002db"),
"collections" : {
"c01" : ISODate("2016-10-27T15:52:04.512Z"),
}
}
One alternative would be to change the schema to something like this:
{
"_id" : ObjectId("581214940911ad3de98002db"),
"collections" : [
{
"id": "c01",
"date": ISODate("2016-10-27T15:52:04.512Z")
},
{
"id": "c02",
"date" : ISODate("2015-11-21T16:06:06.546Z")
}
]
}
in which case removing a document from a would be easy. I am a bit reluctant to do that because it would complicate some of the other queries I would like to support. Thanks!

Answer 1

I prefer the second structure for your schema
{
"_id" : ObjectId("581214940911ad3de98002db"),
"collections" : [
{
"id": "c01",
"date": ISODate("2016-10-27T15:52:04.512Z")
},
{
"id": "c02",
"date" : ISODate("2015-11-21T16:06:06.546Z")
}
]
}
then able to remove from collections like this
db.collectionName.update(
{ },// if you want can add query for specific Id {"_id" : requestId},
{ $pull: { collections: { date: {$lt: yourDate} } } }, // if need can convert iso date string like: new Date(yourDate).toISOString()
{ multi: true }
)