I've got this structure of document, saved in MongoDB 2.6.1, running on Linux:
{
"_id" : "1",
"name" : "Level0",
"childs" : [
{
"id" : "2",
"name" : "Level1",
"childs" : [
{
"id" : "3",
"name" : "Level2",
"childs" : [
{
"id" : "4",
"name" : "Level3-1",
},
{
"id" : "5",
"name" : "Level3-2",
}
]
}
...
Every Element got his childs and every child-element got his own childs until the technical end.
Now I want to Query my MongoDB with something like:
db.categories.find({'childs':{$elemMatch:{$all:['Level19-23']}}})
This Query dont work by the way.
What is a good query to get my elements?
I dont know anything about the children or parents, I've got only the name of the element, and I need the element with all his children.
Anyone got an advise for me, the MongoDB Newbe? :)
Thanks in advance!
Related
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: {$elemMatch: {company:'toyota'}}}).pretty();
read more here : https://docs.mongodb.com/manual/reference/operator/query/elemMatch/
I am pretty new to mongodb, and I am not able to query in my mongo collection.
Structure :
"chapterId":1,
"videos" : [
{
"videoId" : "1",
"videoName" : "about",
"duration" : "12:36",
"tags":["business", "design"]
},
{
"videoId" : "2",
"videoName" : "course",
"duration" : "04:00",
"tags":["technology", "design"]
}
]
I need to select all videos with the tag "business" in chapterId 1.
Can this be done without changing the structure of my collection ?
You should use aggregation so below query will help you
db.collectionName.aggregate(
{"$unwind":"$videos"},
{"$match":{"chapterId":1,"videos.tags":"business"}}
)
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'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
I have two MongoDB collections: The first is a collection that includes frequency information for different IDs and is shown (truncated form) below:
[
{
"_id" : "A1",
"value" : 19
},
{
"_id" : "A2",
"value" : 6
},
{
"_id" : "A3",
"value" : 12
},
{
"_id" : "A4",
"value" : 8
},
{
"_id" : "A5",
"value" : 4
},
...
]
The second collection is more complex and contains information for each _id listed in the first collection (it's called frequency_collection_id in the second collection), but frequency_collection_id may be inside two lists (info.details_one, and info.details_two) for each record:
[
{
"_id" : ObjectId("53cfc1d086763c43723abb07"),
"info" : {
"status" : "pass",
"details_one" : [
{
"frequency_collection_id" : "A1",
"name" : "A1_object_name",
"class" : "known"
},
{
"frequency_collection_id" : "A2",
"name" : "A2_object_name",
"class" : "unknown"
}
],
"details_two" : [
{
"frequency_collection_id" : "A1",
"name" : "A1_object_name",
"class" : "known"
},
{
"frequency_collection_id" : "A2",
"name" : "A2_object_name",
"class" : "unknown"
}
],
}
}
...
]
What I'm looking to do, is merge the frequency information (from the first collection) into the second collection, in effect creating a collection that looks like:
[
{
"_id" : ObjectId("53cfc1d086763c43723abb07"),
"info" : {
"status" : "pass",
"details_one" : [
{
"frequency_collection_id" : "A1",
"name" : "A1_object_name",
"class" : "known",
**"value" : 19**
},
{
"frequency_collection_id" : "A2",
"name" : "A2_object_name",
"class" : "unknown",
**"value" : 6**
}
],
"details_two" : [
{
"frequency_collection_id" : "A1",
"name" : "A1_object_name",
"class" : "known",
**"value" : 19**
},
{
"frequency_collection_id" : "A2",
"name" : "A2_object_name",
"class" : "unknown",
**"value" : 6**
}
],
}
}
...
]
I know that this should be possible with MongoDB's MapReduce functions, but all the examples I've seen are either too minimal for my collection structure, or are answering different questions than I'm looking for.
Does anyone have any pointers? How can I merge my frequency information (from my first collection) into the records (inside my two lists in each record of the second collection)?
I know this is more or less a JOIN, which MongoDB does not support, but from my reading, it looks like this is a prime example of MapReduce.
I'm learning Mongo as best I can, so please forgive me if my question is too naive.
Just like all MongoDB operations, a MapReduce always operates only on a single collection and can not obtain info from another one. So you first step needs to be to dump both collections into one. Your documents have different _id's, so it should not be a problem for them to coexist in the same collection.
Then you do a MapReduce where the map function emits both kinds of documents for their common key, which is their frequency ID.
Your reduce function will then receive an array of two documents for each key: the two documents you have received. You then just have to merge these two documents into one. Keep in mind that the reduce-function can receive these two documents in any order. It can also happen that it gets called for a partial result (only one of the two documents) or for an already completed result. You need to handle these cases gracefully! A good implementation could be to create a new object and then iterate the input-documents copying all existing relevant fields with their values to the new object, so the resulting object is an amalgamation of the input documents.