I've pulled up a document in the mongo shell
car = db.cars.findOne();
...make some changes...
car = db.cars.findOne();
results for same document as if no changes had been made it
There's no save method on a cursor in mongodb. What can I do to persist changes in the shell?
Update. The car document (the first one that's pulled up) has an array of previousdrivers. I have to remove one of the elements and save the doc with it removed.
"previousdrivers" : [
{
"year" : "2011",
"name" : Mr. Zed"
},
{
"year" : "2012",
"name" : "Mr. Bean"
},
{
"year" : "2013",
"name" : "Mr. Smith"
}
]
If you're using the Mongodb shell, you need to use the methods on the collection object to update a document.
For example, if you first:
car = db.cars.findOne();
Then, modify the car instance, you can just use the save method to update the single document (save documentation).
db.cars.save(car);
That will update the single document in the cars collection.
For more advanced usage, you might consider using one of the Array operators which can directly manipulate an array as part of an update.
The findOne() method doesn't return a cursor but a document. You can use any javascript method to manipulate the array. When done, you can call save() for that document. Example
> db.cars.save({make : "ford", gears : [1,2,3,4,5]})
> var doc = db.cars.findOne()
> doc.gears.pop()
5
> db.cars.save(doc)
> db.cars.findOne()
{
"_id" : ObjectId("52239e729a713e4fbc425ed1"),
"make" : "ford",
"gears" : [
1,
2,
3,
4
]
}
Related
I have a double nested array in my MongoDB schema and I'm trying to add an entirely new array element to a second-level nested array using $push. I'm getting the error cannot use the part (...) to traverse the element
A documents have the following structure
{
"_id" : ObjectId("5d8e37eb46c064790a28a467"),
"org-name" : "Manchester University NHS Foundation Trust",
"domain" : "mft.nhs.uk",
"subdomains" : [ {
"name" : "careers.mft.nhs.uk",
"firstSeen" : "2017-10-06 11:32:00",
"history" : [
{
"a_rr" : "80.244.185.184",
"timestamp" : ISODate("2019-09-27T17:24:57.148Z"),
"asn" : 61323,
"asn_org" : "Ukfast.net Limited",
"city" : null,
"country" : "United Kingdom",
"shodan" : {
"ports" : [
{
"port" : 443,
"versions" : [
"TLSv1",
"-SSLv2",
"-SSLv3",
"TLSv1.1",
"TLSv1.2",
"-TLSv1.3"
],
"cpe" : "cpe:/a:apache:http_server:2.4.18",
"product" : "Apache httpd"
}
],
"timestamp" : ISODate("2019-09-27T17:24:58.538Z")
}
}
]
}
]
}
What I'm attempting to do is refresh the details held in the history array and add another entire array entry to represent the most recently collected data for the subdomain.name
The net result is that I will have multiple entries in the history array, each one timestamped the the date that the data was refreshed. That way I have a historical record of changes to any of the data held.
I've read that I can't use $push on a double-nested array but the other advice about using arrayfilters all appear to be related to updating an entry in an array rather than simply appending an entirely new document - unless I'm missing something!
I'm using PyMongo and would simply like to build a new dictionary containing all of the data elements and simply append it to the history.
Thanks!
Straightforward in pymongo:
record = db.mycollection.find_one()
record['subdomains'][0]['history'].append({'another': 'record'})
db.mycollection.replace_one({'_id': record['_id']}, record)
Field is added but then disappears.
Here is the code from within the mongo shell:
> db.users.aggregate([{$addFields:{totalAge:{$sum:"$age"}}}])
{ "_id" : ObjectId("5acb81b53306361018814849"), "name" : "A", "age" : 1, "totalAge" : 1 }
{ "_id" : ObjectId("5acb81b5330636101881484a"), "name" : "B", "age" : 2, "totalAge" : 2 }
{ "_id" : ObjectId("5acb81b5330636101881484b"), "name" : "C", "age" : 3, "totalAge" : 3 }
> db.users.find().pretty()
{ "_id" : ObjectId("5acb81b53306361018814849"), "name" : "A", "age" : 1 }
{ "_id" : ObjectId("5acb81b5330636101881484a"), "name" : "B", "age" : 2 }
{ "_id" : ObjectId("5acb81b5330636101881484b"), "name" : "C", "age" : 3 }
Aggregation only reads data from your collection; it does not edit the collection too. The best way to think about aggregation is that you read some data and manipulate it for your immediate usage.
If you want change it in main source then you must use the update method.
Or an easier way (Not best but easy)
db.users.aggregate([{$addFields:{totalAge:{$sum:"$age"}}}]).forEach(function (x){
db.users.save(x)
})
Nozar's answer was correct, but .save() is now deprecated.
Instead of using his/her exact answer, modify it by using .updateOne and $set.
Old/deprecated answer:
db.users
.aggregate([{$addFields:{totalAge:{$sum:"$age"}}}])
.forEach(function (x){db.users.save(x)})
New/working answer:
db.users
.aggregate([{$addFields:{totalAge:{$sum:"$age"}}}])
.forEach(function (x){db.users.updateOne({name: x.name}, {$set: {totalAge: x.totalAge}})})
Note: In my example, I'm using 'name' to filter (essentially match, in this case) the documents in 'users' collection, but you can use any unique field (e.g. _id field).
Shoutout to Nozar for leading me to the updated answer I provided, as I just used it in my project! (In my project, I used a $match pipeline stage prior to the $addFields pipeline stage, as I was just looking to do this to a single document in my collection, rather than all documents)
The reason is that, your both approach totally different.In aggregation, you have use $addFields in that query you will get a totalAge. But according to your find query, you can get specific data which you have stored in a database.Here you did not calculate totalAge.
I hope you can understand it.
The aggregation pipeline doesn't alter the original data; what it does is to take a temporary in-memory copy of the data and perform a sequence of manipulations on it (still in-memory) and send it to the client.
It's similar to the way you can do db.collection.find().sort() ; the sorting there only changes what is being returned to the client, it doesn't change what is stored in the database.
The only exception is when you use the $out stage, which saves the result of the aggregation to another collection. You can see that, because they had to add a special type of stage to do this, that a normal aggregation does not write back to the stored data.
Use Case
I've got a collection band_profiles and I've got a collection band_profiles_history. The history collection is supposed to store a band_profile snapshot every 24 hour and therefore I am using MongoDB's recommended format for historical tracking: Each month+year is it's own document and in an object array I will store the bandProfile snapshot along with the current day of the month.
My models:
A document in band_profiles_history looks like this:
{
"_id" : ObjectId("599e3bc406955db4cbffe0a8"),
"month" : 7,
"tag_lowercased" : "9yq88gg",
"year" : 2017,
"values" : [
{
"_id" : ObjectId("599e3bc41c073a7418fead91"),
"profile" : {
"_id" : ObjectId("5989a65d0f39d9fd70cde1fe"),
"tag" : "9YQ88GG",
"name_normalized" : "example name1",
},
"day" : 1
},
{
"_id" : ObjectId("599e3bc41c073a7418fead91"),
"profile" : {
"_id" : ObjectId("5989a65d0f39d9fd70cde1fe"),
"tag" : "9YQ88GG",
"name_normalized" : "new name",
},
"day" : 2
}
]
}
And a document in band_profiles:
{
"_id" : ObjectId("5989a6190f39d9fd70cddeb1"),
"tag" : "9V9LRGU",
"name_normalized" : "example name",
"tag_lowercased" : "9v9lrgu",
}
This is how I upsert my documents into band_profiles_history at the moment:
BandProfileHistory.update(
{ tag_lowercased: tag, year, month},
{ $push: {
values: { day, profile }
}
},
{ upsert: true }
)
My problem:
I only want to insert ONE snapshot for every day. Right now it would always push a new object into the object array values no matter if I already have an object for that day or not. How can I achieve that it would only push that object if there is no object for the current day yet?
Putting mongoose aside for a moment:
There is an operation addToSet that will add an element to an array if it doesn't already exists.
Caveat:
If the value is a document, MongoDB determines that the document is a duplicate if an existing document in the array matches the to-be-added document exactly; i.e. the existing document has the exact same fields and values and the fields are in the same order. As such, field order matters and you cannot specify that MongoDB compare only a subset of the fields in the document to determine whether the document is a duplicate of an existing array element.
Since you are trying to add an entire document you are subjected to this restriction.
So I see the following solutions for you:
Solution 1:
Read in the array, see if it contains the element you want and if not push it to the values array with push.
This has the disadvantage of NOT being an atomic operation meaning that you could end up would duplicates anyways. This could be acceptable if you ran a periodical clean up job to remove duplicates from this field on each document.
It's up to you to decide if this is acceptable.
Solution 2:
Assuming you are putting the field _id in the subdocuments of your values field, stop doing it. Assuming mongoose is doing this for you (because it does, from what I understand) stop it from doing it like it says here: Stop mongoose from creating _id for subdocument in arrays.
Next you need to ensure that the fields in the document always have the same order, because order matters when comparing documents in the addToSet operation as stated in the citation above.
Solution 3
Change the schema of your band_profiles_history to something like:
{
"_id" : ObjectId("599e3bc406955db4cbffe0a8"),
"month" : 7,
"tag_lowercased" : "9yq88gg",
"year" : 2017,
"values" : {
"1": { "_id" : ObjectId("599e3bc41c073a7418fead91"),
"profile" : {
"_id" : ObjectId("5989a65d0f39d9fd70cde1fe"),
"tag" : "9YQ88GG",
"name_normalized" : "example name1"
}
},
"2": {
"_id" : ObjectId("599e3bc41c073a7418fead91"),
"profile" : {
"_id" : ObjectId("5989a65d0f39d9fd70cde1fe"),
"tag" : "9YQ88GG",
"name_normalized" : "new name"
}
}
}
Notice that the day field became the key for the subdocuments on the values. Notice also that values is now an Object instead of an Array.
No you can run an update query that would update values.<day> only if values.<day> didn't exist.
Personally I don't like this as it is using the fact that JSON doesn't allow duplicate keys to support the schema.
First of all, sadly mongodb does not support uniqueness of a field in an array of a collection. You can see there is major bug opened for 7 years and not closed yet(that is a shame in my opinion).
What you can do from here is limited and all is on application level. I had same problem and solve it in application level. Do something like this:
First read your document with document _id and values.day.
If your reading in step 1 returns null, that means there is no record on values array for given day, so you can push the new value(I assume band_profile_history has record with _id value).
If your reading in step 1 returns a document, that means values array has a record for given day. In that case you can use setoperation with $operator.
Like others said, they will be not atomic but while you are dealing with your problem in application level, you can make whole bunch of code synchronized. There will be 2 queries to run on mongodb among of 3 queries. Like below:
db.getCollection('band_profiles_history').find({"_id": "1", "values.day": 3})
if returns null:
db.getCollection('band_profiles_history').update({"_id": "1"}, {$push: {"values": {<your new band profile history for given day>}}})
if returns not null:
db.getCollection('band_profiles_history').update({"_id": "1", "values.day": 3}, {$set: {"values.$": {<your new band profile history for given day>}}})
To check if object is empty
{ field: {$exists: false} }
or if it is an array
{ field: {$eq: []} }
Mongoose also supports field: {type: Date} so you can use it instead counting a days, and do updates only for current date.
I have a collection called books.
When use browse a particular book, I get the book by id.
But I also want to increase the view count by 1 each time I read the doc.
I can use 2 commands: one to read and another to update the views counter by 1
Is there a wayy to do this by single command like findAndModify?
How to use that using CSharp driver?
Books:
{
{
"_id": "1"
"title" : "Earth Day",
"author" : "John ",
"pages" : 212,
"price" : 14.5,
"views" : 1000
},
{
"_id": "2"
"title" : "The last voyage",
"author" : "Bob",
"pages" : 112,
"price" : 10.5,
"views" : 100
}
}
I have this:
var query = Query.And(Query.EQ("_id", id));
var sortBy = SortBy.Null;
var update = Update.Inc("views", 1);
var result = Books.FindAndModify(query, sortBy, update, true);
But how do I get the matching document back?
EDIT: I got it working..
return result.GetModifiedDocumentAs<T>();
My question is this call GetModifiedDocumentAs() will hit the database again?
No, it won't hit the database again.
When in doubt about things like this, look at the source. It shows that the GetModifiedDocumentAs method just accesses the resulting doc from the existing Response object and casts it to the requested type.
I'm a newbie with MongoDB, and am trying to store user activity performed on a site. My data is currently structured as:
{ "_id" : ObjectId("4decfb0fc7c6ff7ff77d615e"),
"activity" : [
{
"action" : "added",
"item_name" : "iPhone",
"item_id" : 6140,
},
{
"action" : "added",
"item_name" : "iPad",
"item_id" : 7220,
}
],
"name" : "Smith,
"user_id" : 2
}
If I want to retrieve, for example, all the activity concerning item_id 7220, I would use a query like:
db.find( { "activity.item_id" : 7220 } );
However, this seems to return the entire document, including the record for item 6140.
Can anyone suggest how this might be done correctly? I'm not sure if it's a problem with my query, or with the structure of the data itself.
Many thanks.
You have to wait the following dev: https://jira.mongodb.org/browse/SERVER-828
You can use $slice only if you know insertion order and position of your element.
Standard queries on MongoDb always return all document.
(question also available here: MongoDB query to return only embedded document)