I have a what I consider to be a pretty straight forward search. I am developing it on MOngoDB locally but deploying it for DocumentDB on AWS. The function that I've written looks something like this:
if (searchCategory) {
return [
{
$match: {
$or: [
{ title: params.searchString },
{ description: params.searchString },
{ workingNotes: params.searchString },
],
active: true,
},
},
];
}
This query used to not have the $match statement around it and it worked fine, but something that we wanted to do was to use reference fields in our model for searching linked items as well. So we have something like this in our model:
appendix: [{type: Schema.Types.ObjectId, ref: "document"}],
Now when I fire off the search query, I get an error back saying "Aggregation stage not supported: '$lookup on multiple join conditions and uncorrelated subquery.'"
Adding the reference field and the $match were the only changes made to the functionality, which worked before we added those.
Based off the documentation I've read about DocumentDB, the $match operator is supported, so it's possible I am missing something else about how to structure the query or handle the reference fields but I've been unable to determine what that might be.
Any help would be appreciated. Thanks!
Related
I've got a collection in MongoDB whose simplified version looks like this:
Dealers = [{
Id: 123,
Name: 'Someone',
Email: 'someone#somewhere.com',
Vehicles: [
{
Id: 1234,
Make: 'Honda',
Model: 'Civic'
},
{
Id: 2345,
Make: 'Ford',
Model: 'Focus'
},
{
Id: 3456,
Make: 'Ford',
Model: 'KA'
}
]
}]
And my Mongoose Model looks a bit like this:
const vehicle_model = mongoose.Schema({
Id: {
Type: Number
},
Email: {
Type: String
},
Vehicles: [{
Id: {
Type: Number
},
Make: {
Type: String
},
Model: {
Type: String
}
}]
})
Note the Ids are not MongoDB Ids, just distinct numbers.
I try doing something like this:
const response = await vehicle_model.findOne({ 'Id': 123, 'Vehicles.Id': 1234 })
But when I do:
console.log(response.Vehicles.length)
It's returned all the Vehicles nested records instead on the one I'm after.
What am I doing wrong?
Thanks.
This question is asked very frequently. Indeed someone asked a related question here just 18 minutes before this one.
When query the database you are requesting that it identify and return matching documents to the client. That is a separate action entirely than asking for it to transform the shape of those documents before they are sent back to the client.
In MongoDB, the latter operation (transforming the shape of the document) is usually referred to as "Projection". Simple projections, specifically just returning a subset of the fields, can be done directly in find() (and similar) operations. Most drivers and the shell use the second argument to the method as the projection specification, see here in the documentation.
Your particular case is a little more complicated because you are looking to trim off some of the values in the array. There is a dedicated page in the documentation titled Project Fields to Return from Query which goes into more detail about different situations. Indeed near the bottom is a section titled Project Specific Array Elements in the Returned Array which describes your situation more directly. In it is where they describe usage of the positional $ operator. You can use that as a starting place as follows:
db.collection.find({
"Id": 123,
"Vehicles.Id": 1234
},
{
"Vehicles.$": 1
})
Playground demonstration here.
If you need something more complex, then you would have to start exploring usage of the $elemMatch (projection) operator (not the query variant) or, as #nimrod serok mentions in the comments, using the $filter aggregation operator in an aggregation pipeline. The last option here is certainly the most expressive and flexible, but also the most verbose.
{
questions: {
q1: "",
}
}
result after updating:
{
questions: {
q1: "",
q2: ""
}
}
I want to add q2 inside questions, without overwritting what's already inside it (q1).
One solution I found is to get the whole document, and modify it on my backend, and send the whole document to replace the current one. But it seems really in-effiecient as I have other fields in the document as well.
Is there a query that does it more efficiently? I looked at the mongodb docs, didn't seem to find a query that does it.
As turivishal said, you can use $set like this
But you also can use $addFields in this way:
db.collection.aggregate([
{
"$match": {
"questions.q1": "q1"
}
},
{
"$addFields": {
"questions.q2": "q2"
}
}
])
Example here
Also, reading your comment where you say Cannot create field 'q2' in element {questions: "q1"}. It seems your original schema is not the same you have into your DB.
Your schema says that questions is an object with field q1. But your error says that questions is the field and q1 the value.
Say I have an entry in the inventory collection that looks like
{ _id: 1, item: "polarizing_filter", tags: [ "electronics", "camera" ]}
and I issue the command
db.inventory.update(
{ _id: 1 },
{ $addToSet: { tags: "accessories" } }
)
I have an oplog tailer, and would like to know that, specifically, "accessories" has been added to this document's tags field. As far as I can tell, the oplog always normalizes commands to use $set and $unset to maintain idempotency. In this case, the field of the entry describing the update would show something like
{$set : { tags : ["electronics", "camera", "accessories"] } }
which makes it impossible to know which tags were actually added by this update. Is there anyway to do this? I'm also curious about the analogous case in which fields are modified through deletion, e.g. through $pull. Solutions outside of the realm of an oplog tailer are welcome, as well as pointers to documentation of this command normalization process - I can't find it.
Thanks!
So I've got an application that uses a lot of embedded documents, which is fine. However I've noticed that some embedded documents aren't displayed when you show collections in Mongo shell.
Normally this isn't an issue, but whilst dicking with setting embedded documents, I accidentally added an empty entry to one of the entries. I'd normally do something like this to remove the entry db.collection.remove({_id: ObjectId('<OBJECT_ID>')}), but since some of these aren't actual collections I'm unable to do it like this.
I'm also not sure how I'd splice out this successfully while actually removing the document. I could splice it out of the entry, but I have a feeling it would leave that embedded document floating around somewhere in the DB.
Any ideas how to do this?
To give you an idea what I'm talking about, an example of the entry:
entry = {
_id: ObjectId('blah blah blah'),
name: {
first: 'example',
last: 'city'
},
log : [
{
_id: ObjectId('some id'),
action: 'whatever',
someField: 'etc.'
},
{
_id: ObjectId('another id')
},
{
_id: ObjectId('yet another id'),
action: 'who cares',
someField: 'data'
}
]
}
If you want to remove one of the log entries, then you want the $pull operator.
The format would be something like:
db.collection.update({_id:<id-of-document-to-update>},
{$pull:{"log._id":<id-of-log-entry-to-remove>"}}
)
This says, find document with certain _id and remove from log array an entry with certain sub_id.
I've just started to look at meteor and I'm stuck trying to update a record within an array within a record. Say i have a document that looks something like this:
Users:
{
_id: "somerandom",
name: "name1",
items, [
{
name: "item1",
data: "somedata",
...
},
{
name: "item2",
data: "somedata",
...
}
],
...
},
...
And I want to update the data of items 'item1'. I can't find anything on how to do this in meteor, but from what I have read about MongoDB I think that the correct way would be something like
Users.update({_id: userId, "items.name": 'item1}, {$set: {"items.$.data": newData}});
but since the MongoDB used in Meteor doesn't support $ it won't work, on the other hand I might be way of how this should be done.
Does anyone have a solution for this?
Use Meteor.methods() and implement your database operation on the server side and call it using Meteor.call() from the client. This feature is not yet implemented in Meteor and it is documented here.
You can read more in the discussion on this issue raised on Github, here.
I found a workaround at meteor's github https://github.com/meteor/meteor/blob/master/examples/parties/model.js
The idea is to first get the index of the array-item you want to change and then use that index instead of $. So in this case it would be something like
user = Users.findOne(userId);
index = _.indexOf(_.pluck(user.items, 'name'), 'item1');
modifier = {$set: {}};
modifier.$set["items." + index + ".data"] = newData;
Users.update(userId, modifier);