I'm using the Java driver withe document that looks like this (a real test example):
{
"_id" : ObjectId("5207fe359b88bfa6f90a82b0"),
"meta_id" : "d6eb1b13-50c7-473f-8348-b5a638a542a0",
"name" : "Fake Name Inc.",
"created" : ISODate("2013-08-11T21:12:21.533Z"),
"members" : {
"5207fe359b88bfa6f90a82af" : [
"Admin",
"User"
]
}
}
I want to select the string array at the path "members.5207fe359b88bfa6f90a82af" (which is a list of roles).
I'm at a loss as to how to do that. It looks like a projection would work here, but I'm new enough to Mongo that the way the projection is written is not obvious.
I can of course load the whole object or maybe even just the "members" field, but I think I should be able to select just exactly the data I'm after.
So, does anyone have an idea of how such a query would be written?
Note: This question suggests that maybe I need to change the structure of the document to make things easier: MongoDB - Query by sub-tree
You can use dot notation in the projection parameter of find to do this. In the shell:
db.test.find(
{_id : ObjectId("5207fe359b88bfa6f90a82b0")},
{'members.5207fe359b88bfa6f90a82af': 1, _id: 0})
Returns:
{
"members": {
"5207fe359b88bfa6f90a82af": [
"Admin",
"User"
]
}
}
Related
Given a collection of MongoDb documents with a property "myContacts" like this:
{
"_id": 123,
"myContacts" : {
"contacts" : {
"10" : {
"_id" : NumberLong(10),
"name" : "c1",
"prop" : true
},
"20" : {
"_id" : NumberLong(20),
"name" : "c2"
},
}
}
}
I want to select all documents, where at least one contact lacks the "prop" field.
I figured out a general query:
db.getCollection('xyz').find({ 'myContacts.contacts.???.prop': { $exists: false } })
The problem is that IDs of the contacts are part of the path and I cannot know them ahead. I want sth like 'myContacts.contacts.$anyChild.prop', but cannot find sth similar in the mongo docs.
Does it mean there is no way to do it?
PS: I cannot change the document structure, a live app uses it. I've spent some time with Google and my bet it's not possible. I however would like an opinion from people who have experience with Mongo.
Thank you guys for helpful comments, this got me going! I could get the results I wanted with:
db.getCollection('xyz').aggregate([{$project: {_id:1, contacts:{$objectToArray: "$myContacts.contacts"}}}, {$match: {"contacts.v.prop" : null}}])
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" }}}).
If I have a document as follows:
{
"_id" : ObjectId("54986d5531a011bb5fb8e0ee"),
"owner" : "54948a5d85f7a9527a002917",
"type" : "group",
"deleted" : false,
"participants" : {
"54948a5d85f7a9527a002917" : {
"last_message_id" : null
},
"5491234568f7a9527a002917" : {
"last_message_id" : null
}
"1234567aaaa7a9527a002917" : {
"last_message_id" : null
}
},
}
How do I do a simple filter for all documents this have participant "54948a5d85f7a9527a002917"?
Thanks
Trying to query structures like this does not work well. There are a whole whole host of problems with modelling like this, but the most clear problem is using "data" as the names for "keys".
Try to think a little RDBMS like, at least in the concepts of the limitations to what a database cannot or should not do. You wouldn't design a "table" in a schema that had something like "54948a5d85f7a9527a002917" as the "column" name now would you? But this is essentially what you are doing here.
MongoDB can query this, but not in an efficient way:
db.collection.find({
"participants.54948a5d85f7a9527a002917": { "$exists": true }
})
Naturally this looks for the "presence" of a key in the data. While the query form is available, it does not make efficient use of such things as indexes where available as indexes apply to "data" and not the "key" names.
A better structure and approach is this:
{
"_id" : ObjectId("54986d5531a011bb5fb8e0ee"),
"owner" : "54948a5d85f7a9527a002917",
"type" : "group",
"deleted" : false,
"participants" : [
{ "_id": "54948a5d85f7a9527a002917" },
{ "_id": "5491234568f7a9527a002918" },
{ "_id": "1234567aaaa7a9527a002917" }
]
}
Now the "data" you are looking for is actual "data" associated with a "key" ( possibly ) and inside an array for binding to the parent object. This is much more efficient to query:
db.collection.find({
"participants._id": "54948a5d85f7a9527a002917"
})
It's much better to model that way than what you are presently doing and it makes sense to the consumption of objects.
BTW. It's probably just cut and paste in your question but you cannot possibly duplicate keys such as "54948a5d85f7a9527a002917" as you have. That is a basic hash rule that is being broken there.
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.
{ _id : ObjectId(...),
name : "...",
addresses : [ {
context : "home" ,
loc : [ 55.5, 42.3 ]
} ,
{
context : "office",
loc : [ -74 , 44.74 ]
}
]
}
address.loc is "2d" indexed.
I want to write a query that should give me all the document that are $near a location and the context is office.
I wrote some thing like:
db.coll.find({'address.loc':{$near:[lat,lng]}, 'address.context' : "office"});
Above query doesn't give me results that wanted. It searches for location in the entire "Address" array and then searches for context in the entire array.
I would like to search for same array location and same context. I know it could be done by $elemMatch but when I try to use it, it says there is no 2d index available or 2dsphere index.
I am new to MongoDB and not sure how should I write my query.
I've tried the query and it seems to work as you intend with the $elemMatch operator. I think the problem is that you have a typo in your query where address is used instead of addresses. Your query should look like:
db.coll.find({ 'addresses.loc':{$near:[lat,lng]}, addresses: { $elemMatch: {context: "office"} } });