based on this :
db.room.save({name:'public',msg:[{to:'Jo',msg:'whats up'},{to:'Jo',msg:'dude?'}]})
db.room.find()
> { "_id" : ObjectId("4f86282a87850ac4bfe9a664"), "name" : "public", "msg" : [ { "to" : "Jo", "msg" : "whats up" }, { "to" : "Jo", "msg" : "dude?" } ] }
I would like to get the following result:
db.room.find(????)
> {"name" : "public", "to" : "Jo", "msg" : "whats up"}
> {"name" : "public", "to" : "Jo", "msg" : "dude?"}
What query should i use in order to achieve this ?
The short answer is that it is not possible to retrieve individual embedded documents. Only top-level documents are returned.
There is a feature request for this functionality. "Support for positional ($) operator in fields to return specifier" - https://jira.mongodb.org/browse/SERVER-828
This feature request is slated for version 2.1.1, but this is subject to change.
A similar question was asked on Google Groups a while back, "Retrieving DBObject from an array of DBObjects" - http://groups.google.com/group/mongodb-user/browse_thread/thread/7d2c8919dd6c4dd8 the question is on the Java Driver specifically, but the answer is still applicable.
If you want to modify embedded documents, you can do so as described in the Google Groups response. Additionally, the new Aggregation Framework contains an $unwind method, which you might want to experiment with. If you would like to print out only the embedded documents, you will have to do it via your application, or consider changing your document structure such that the documents that you want to display are top-level.
Hope this helps!
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 $push on a double-nested array but the other advice about using arrayfilters all appear to be related to updating an entry in an array rather than simply appending an entirely new document - unless I'm missing something!
I'm using PyMongo and would simply like to build a new dictionary containing all of the data elements and simply append it to the history.
Thanks!
Straightforward in pymongo:
record = db.mycollection.find_one()
record['subdomains'][0]['history'].append({'another': 'record'})
db.mycollection.replace_one({'_id': record['_id']}, record)
I searched for similar questions but couldn't find any. Feel free to point me in their direction.
Say I have this data:
{ "_id" : ObjectId("5694c9eed4c65e923780f28e"), "name" : "foo1", "attr" : "foo" }
{ "_id" : ObjectId("5694ca3ad4c65e923780f290"), "name" : "foo2", "attr" : "foo" }
{ "_id" : ObjectId("5694ca47d4c65e923780f294"), "name" : "bar1", "attr" : "bar" }
{ "_id" : ObjectId("5694ca53d4c65e923780f296"), "name" : "bar2", "attr" : "bar" }
If I want to get the latest record for each attribute group, I can do this:
> db.content.aggregate({$group: {_id: '$attr', name: {$last: '$name'}}})
{ "_id" : "bar", "name" : "bar2" }
{ "_id" : "foo", "name" : "foo2" }
I would like to have my data grouped by attr and then sorted by _id so that only the latest record remains in each group, and that's how I can achieve this. BUT I need a way to avoid naming all the fields that I want in the result (in this example "name") because in my real use case they are not known ahead.
So, is there a way to achieve this, but without having to explicitly name each field using $last and just taking all fields instead? Of course, I would sort my data prior to grouping and I just need to somehow tell Mongo "take all values from the latest one".
See some possible options here:
Do multiple find().sort() queries for each of the attr values you
want to search.
Grab the original _id of the $last doc, then do a findOne() for each of those values (this is the more extensible option).
Use the $$ROOT system variable as shown here.
This wouldn't be the quickest operation, but I assume you're using this more for analytics, not in response to a user behavior.
Edited to add slouc's example posted in comments:
db.content.aggregate({$group: {_id: '$attr', lastItem: { $last: "$$ROOT" }}}).
This my code:
db.test.find() {
"_id" : ObjectId("4d3ed089fb60ab534684b7e9"),
"title" : "Sir",
"name" : {
"_id" : ObjectId("4d3ed089fb60ab534684b7ff"),
"first_name" : "Farid"
},
"addresses" : [
{
"city" : "Baku",
"country" : "Azerbaijan"
},{
"city" : "Susha",
"country" : "Azerbaijan"
},{
"city" : "Istanbul",
"country" : "Turkey"
}
]
}
I want get output only all city. Or I want get output only all country. How can i do it?
I'm not 100% about your code example, because if your 'find' by ID there's no need to search by anything else... but I wonder whether the following can help:
db.test.insert({name:'farid', addresses:[
{"city":"Baku", "country":"Azerbaijan"},
{"city":"Susha", "country":"Azerbaijan"},
{"city" : "Istanbul","country" : "Turkey"}
]});
db.test.insert({name:'elena', addresses:[
{"city" : "Ankara","country" : "Turkey"},
{"city":"Baku", "country":"Azerbaijan"}
]});
Then the following will show all countries:
db.test.aggregate(
{$unwind: "$addresses"},
{$group: {_id:"$country", countries:{$addToSet:"$addresses.country"}}}
);
result will be
{ "result" : [
{ "_id" : null,
"countries" : [ "Turkey", "Azerbaijan"]
}
],
"ok" : 1
}
Maybe there are other ways, but that's one I know.
With 'cities' you might want to take more care (because I know cities with the same name in different countries...).
Based on your question, there may be two underlying issues here:
First, it looks like you are trying to query a Collection called "test". Often times, "test" is the name of an actual database you are using. My concern, then, is that you are trying to query the database "test" to find any collections that have the key "city" or "country" on any of the internal documents. If this is the case, what you actually need to do is identify all of the collections in your database, and search them individually to see if any of these collections contain documents that include the keys you are looking for.
(For more information on how the db.collection.find() method works, check the MongoDB documentation here: http://docs.mongodb.org/manual/reference/method/db.collection.find/#db.collection.find)
Second, if this is actually what you are trying to do, all you need to for each collection is define a query that only returns the key of the document you are looking for. If you get more than 0 results from the query, you know documents have the "city" key. If they don't return results, you can ignore these collections. One caveat here is if data about "city" is in embedded documents within a collection. If this is the case, you may actually need to have some idea of which embedded documents may contain the key you are looking for.
I am trying to filter mongo data by using the below query in mongodb version 2.6.1 but getting error.
MongoDB version 2.4.6 (Working):
> db.BC_1839.find({data: {$elemMatch:{$where : "this.First_name.toLowerCase().indexOf('kim') ==0"}}});
output:
{
"_id" : ObjectId("53719a9d5b9e5c8c110001b9"),
"data" : [
{
"First_name" : "Kimberely",
"Last_name" : "Weyman",
"Company_name" : "Scientific Agrcltl Svc Inc",
"Address" : "7721 Harrison St",
"City" : "Kingsway West",
"State" : "NS",
"Post" : "2208",
"Phone1" : "02-7091-8948",
"Phone2" : "0441-151-810",
"Email" : "kweyman#weyman.com.au",
"Web" : "http://www.scientificagrcltlsvcinc.com.au",
"active" : "true"
}
],
"history" : [
{
"timestamp" : "2014-05-13 06:07:55",
"event": "creation",
"createdby" : "Srikesh Infotech",
"creation_data" : [
{
"crm_base_contact_id" : "1839",
"crm_imported_files_id" : "1464"
}
]
},
{
"timestamp" : "2014-05-13 06:09:05",
"event" : "Task",
"createdby" : "Srikesh Infotech",
"Task_data" : [
{
"Campaign ID" : "193",
"Campagin Name" : "Test Campa1"
}
]
}
],
"ref" : [
{ "crm_base_contact_id" : "1839", "crm_imported_files_id" : "1464" }
]
}
MongoDB version 2.6.1(Not Working):
> db.BC_1839.find({data: {$elemMatch:{$where : "this.First_name.toLowerCase().indexOf('kim') ==0"}}});
output:
error: {
"$err" : "Can't canonicalize query: BadValue $elemMatch cannot contain $
where expression",
"code" : 17287
}
Same query executes in mongodb version 2.4.6 but not in mongodb version 2.6.1 Why???
It shouldn't have worked in earlier versions at all, as at the very least you have modified the scoping of this to now refer to "data" as a top level element. In short, this is no longer allowed and you really should not be using JavaScript methods unless you absolutely have to. Even then, there is probably still a better way in most cases.
But in fact this is an un-necessary use of JavaScript matching as it is not required when there are other operators existing that will do this.
You should be using a $regex form instead:
db.docs.find({ "data.First_name": /^kim/i })
Or anywhere within the field, remove the caret ^:
db.docs.find({ "data.First_name": /kim/i })
Which is pretty much as inefficient as JavaScript execution but not as much as there is not the overhead of processing through that interpreter engine. And of course it works everywhere.
Also think about what a query relying on JavaScript to resolve is actually doing:
Invokes a JavaScript interpreter instance
Converts BSON document types per document to JavaScript types
Evaluates JavaScript code in the interpreter per document
Casts JavaScript true|false back as a result per document
Considering that $regex ( but with a case insensitive match which is not optimal ) is doing the same operations but using the "pcre" C library natively without conversion and recasting per document, then it is clearly the sane choice of the two.
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)