TL;DR:
db.collection.update( _id: 'x' , $pull: embedded_doc: _id: 'y' )
Queries are wrote for the mongo shell
Dot based access
If you have been using
MongoDB for some time, then there are big chances that you will know the "dot-based access" on the
find queries. This is the easier way to write those queries and will probably want to keep using that. Like:
db.collection.find( _id: 'x', 'embedded_doc._id': 'y' )
The thing is that does not work with everything, like: Arrays of embedded documents!
Little example schema
Let's suppose the following little schema (written for
Mongoose):
A = new Schema(
w: String,
x: String
);
Document = new Schema(
embedded_doc: [A]
);
The collection of
Document is called
documents.
Updating arrays
If the arrays are not embedded documents I can actually just use a regular
update like with any other field combined with a
$set and change all the array like:
db.documents.update( _id: 'x', $set: array: [
a: 1 ,
a: 2 ,
a: 3
] )
And using conveniently
$pull and
$addToSet. But when it comes to embedded documents the history is very different. You can't make a simple
$set because it will give you an error related to
ModId which you can't change. So you really need to use
$push,
$addToSet,
$pull and it's friends.
So all those you can do it as in the manual, but what if you want to make a
$pull over an array of objects and
w and
x are not unique? Well, that's why you probably made them an embedded document! Then you have the
_id and you try to use the dot notation like:
db.documents.update( _id: 'x' , $pull: "embedded_doc._id": 'y' )
And it looks good, except that it wont work. You have to use the complete syntax like:
db.documents.update( _id: 'x' , $pull: embedded_doc: _id: 'y' )
