I'm new to mongodb and javascript, and have been reading the manual, but I can't seem to put the pieces together to solve the following problem.. I was wondering if you can kindly help.
I have two collections "places" and "reviews".
One document in "places" collection is as follows:
{
"_id" : "004571a7-afe4-4124-996e-b6ec779db494",
"name" : "wakawaka place",
"address" : {
"address" : "12 ad avenue",
"city" : "New York",
},
"review" : [
{
"id" : "i32347",
"review_list" : [
"r123456",
"r123457"
],
}
]
}
The "review" array can be empty for some documents.
And in the "reviews" collection, every document in the collection represents a review:
{
"_id" : ObjectId("53c913689c8e91a5a9c4047f"),
"user_id" : "useridhere",
"review_id" : "r123456",
"attraction_id" : "i32347",
"content" : "review content here"
}
What I would like to achieve is, for each place that has reviews, get the content of each review from the "review" collection and store them together in another new collection.
I'd be grateful for any suggestions on how to go about this.
Thanks
Related
I recently encountered an issue, and I'd like to solve it. If anyone would give any suggestion I'll be grateful.
I have documents that represent "users" and each document has a subarray that is responsible to save some codes, they can be many for each user. The matter is, each user cannot have duplicate codes in its specific array, but at the same time, in this case, each document should be isolated, for example, being possible to have two or more identical codes but since they are from different documents(users).
In short, the subarray("codes") cannot have individually duplicated codes(code), but that shouldn't interfere with other documents
I could do that in the application part, but I think doing that guarantee directly on DB, it's safer.
Is it possible to create indexes for this specific situation?
Example of two documents representing their respective users:
{ // Document of user 1
"_id" : "1", //user 1 and its codes
"codes" : [
{
"code" : "1111",
"description" : "code 1",
},
{
"code" : "2222",
"description" : "code 2",
},
{
"code" : "3333",
"description" : "code 3",
}
]
},
{ // Document of user 2
"_id" : "2", //user 2 and its codes
"codes" : [
{
"code" : "1111",
"description" : "code 1",
},
{
"code" : "4444",
"description" : "code 2",
},
{
"code" : "2222",
"description" : "code 3",
}
]
}
Thank you!
Use https://docs.mongodb.com/manual/reference/operator/update/addToSet/ to maintain uniqueness of code subdocuments. You will need to ensure that you always specify code fields in the same order (e.g. code, description).
Following is example of table in mongodb, I have multiple records for companies like this, which I need help with.
I wanted to query the below table wherein using value from company I should be able to retrieve the name of all the cars.
"vehicles" : [
{
"source" : "jeep",
"tag" : [
{
"company" : "toyota",
"name" : "fortuner"
},
{
"company" : "rangerover",
"name" : "discovery"
]
}
]
Thanks...
try this :
db.vehicles.find({tag: {$elemMatch: {company:'toyota'}}}).pretty();
read more here : https://docs.mongodb.com/manual/reference/operator/query/elemMatch/
I need get a specific object in array of array in MongoDB.
I need get only the task object = [_id = ObjectId("543429a2cb38b1d83c3ff2c2")].
My document (projects):
{
"_id" : ObjectId("543428c2cb38b1d83c3ff2bd"),
"name" : "new project",
"author" : ObjectId("5424ac37eb0ea85d4c921f8b"),
"members" : [
ObjectId("5424ac37eb0ea85d4c921f8b")
],
"US" : [
{
"_id" : ObjectId("5434297fcb38b1d83c3ff2c0"),
"name" : "Test Story",
"author" : ObjectId("5424ac37eb0ea85d4c921f8b"),
"tasks" : [
{
"_id" : ObjectId("54342987cb38b1d83c3ff2c1"),
"name" : "teste3",
"author" : ObjectId("5424ac37eb0ea85d4c921f8b")
},
{
"_id" : ObjectId("543429a2cb38b1d83c3ff2c2"),
"name" : "jklasdfa_XXX",
"author" : ObjectId("5424ac37eb0ea85d4c921f8b")
}
]
}
]
}
Result expected:
{
"_id" : ObjectId("543429a2cb38b1d83c3ff2c2"),
"name" : "jklasdfa_XXX",
"author" : ObjectId("5424ac37eb0ea85d4c921f8b")
}
But i not getting it.
I still testing with no success:
db.projects.find({
"US.tasks._id" : ObjectId("543429a2cb38b1d83c3ff2c2")
}, { "US.tasks.$" : 1 })
I tryed with $elemMatch too, but return nothing.
db.projects.find({
"US" : {
"tasks" : {
$elemMatch : {
"_id" : ObjectId("543429a2cb38b1d83c3ff2c2")
}
}
}
})
Can i get ONLY my result expected using find()? If not, what and how use?
Thanks!
You will need an aggregation for that:
db.projects.aggregate([{$unwind:"$US"},
{$unwind:"$US.tasks"},
{$match:{"US.tasks._id":ObjectId("543429a2cb38b1d83c3ff2c2")}},
{$project:{_id:0,"task":"$US.tasks"}}])
should return
{ task : {
"_id" : ObjectId("543429a2cb38b1d83c3ff2c2"),
"name" : "jklasdfa_XXX",
"author" : ObjectId("5424ac37eb0ea85d4c921f8b")
}
Explanation:
$unwind creates a new (virtual) document for each array element
$match is the query part of your find
$project is similar as to project part in find i.e. it specifies the fields you want to get in the results
You might want to add a second $match before the $unwind if you know the document you are searching (look at performance metrics).
Edit: added a second $unwind since US is an array.
Don't know what you are doing (so realy can't tell and just sugesting) but you might want to examine if your schema (and mongodb) is ideal for your task because the document looks just like denormalized relational data probably a relational database would be better for you.
I have two collection as bellow products has reference of user. i search product by name & in return i want combine output of product and user using map reduce method
user collection
{
"_id" : ObjectId("52ac5dd1fb670c2007000000"),
"company" : {
"about" : "This is textile machinery dealer",
"contactAddress" : [{
"address" : "abcd",
"city" : "52ac4bc6fb670c1007000000",
"zipcode" : "39as46as80"
},{
"address" : "abcd",
"city" : "52ac4bc6fb670c1007000000",
"zipcode" : "39as46as80"
}],
"fax" : "58784868",
"mainProducts" : "ads,asd,asd",
"mobileNumber" : "9537236588",
"name" : "krishna steels",
}
"user" : ObjectId("52ac4eb7fb670c0c07000000")
}
product colletion
{
"_id" : ObjectId("52ac5722fb670cf806000002"),
"category" : "52a2a9cc48a508b80e00001d",
"deliveryTime" : "10 days after received the ",
"price" : {
"minPrice" : "2000",
"maxPrice" : "3000",
"perUnit" : "5288ac6f7c104203e0976851",
"currency" : "INR"
},
"productName" : "New Mobile Solar Charger with Carabiner",
"rejectReason" : "",
"status" : 1,
"user" : ObjectId("52ac4eb7fb670c0c07000000")
}
This cannot be done. Mongo support Map Reduce only on one collection. You could try to fetch and merge in a java collection. Couple of days back I solved a similar problem using java collection.
Click to see similar response about joins and multi collection not supported in mongo.
This can be done using two map reduces.
You run your first MR and then you reduce out the second MR onto the results of the first.
You shouldn't do this though. JOINs are not designed to be done through MR, in fact it sounds like you are trying to do this MR with inline output which in itself is a very bad idea.
MRs are not designed to run inline to the application.
You would be better off doing the JOIN else where.
My first adventure into Mongo. Please save me some time by answering the following. This is the schema.
"_id" : 1,
"FullName" : "Full Name",
"Email" : "email#email.com",
"FacebookId" : NumberLong(0),
"LastModified" : ISODate("2012-04-11T09:26:10.955Z"),
"Connections" : [{
"_id" : 7,
"FullName" : "Fuller name",
"Email" : "connections#email.com",
"FacebookId" : NumberLong(0),
"LastModified" : ISODate("0001-01-01T00:00:00Z")
},
....
Given an id of a single top user, i'd like to return all of the Emails in the Connections array, and preferably, just the emails. What's the querystring? Much obliged!
You can't get only values from the sub-objects in MongoDB.
If you do a query like this:
db.test.find({"_id": 1}, {"Connections.Email":1});
you will get this kind of response:
{
"_id": 1,
"Connections" : [ {"Email":"connections#email.com"},
{"Email":"foo#example.com"} ]
}
This is the closest you can get with a simple query and field selection from MongoDB.
You can then filter out the e-mails values in your code with a simple foreach.