I'm using mongodb to store my data. My collection consists in a list of objects identified by a type a list of other objects for each of them.
An example of my collection is:
[
{
"type": "a",
"properties": [
{
"value": "value_a",
"date": "my_date_a"
},
{
"value": "value_b",
"date": "my_date_b"
},
...
]
},
...
]
Based on the above data structure, I want to retrieve all collections by a given type, taking for each of them only one element in the nested array (reducing the nested list to a list of only one element).
So, given a type "a", an example of the result may be:
[
{
"type": "a",
"properties": [
{
"value": "value_a",
"date": "my_date_a"
}
]
},
...
]
I'm started trying this query { "type": "a" } to filter the collections. But, how can I do to take only one "properties" element? I cannot use the "slice" operator.
Thanks a lot.
I'm assuming from your reference to slice, that you're not interested in matching a particular nested element, and rather just getting a value at a fixed index (eg, 0).
If you're willing to use the aggregation pipeline, you can use arrayElementAt within a projection:
db.collection.aggregate([
// matches documents with type 'a'
{ $match: { type: 'a' } },
// creates a new document for each
{ $project: {
// that contains the original value for type
type: 1,
// and the first element from the original properties for properties
properties: { $arrayElemAt: [ "$properties", 0 ] }
} }
])
Related
I work on a project where the output of one of our APIs is a JSON array. I'd like to encapsulate this array inside an object.
I try to use a JOLT transformation (this is the first time I use this tool) to achieve this. I've already searched through a lot of example, but I still can't figure out what my JOLT specification has to be to perform the transformation. I can't find what I am looking for.
For example, if my input is like this:
[
{
"id": 1,
"name": "foo"
},
{
"id": 2,
"name": "bar"
}
]
I'd like the output to be:
{
"list":
[
{
"id": 1,
"name": "foo"
},
{
"id": 2,
"name": "bar"
}
]
}
In short, I just want to put my array inside a field of another object.
You can use a shift transformation spec such as
[
{
"operation": "shift",
"spec": {
"*": "list[]"
}
}
]
where "*" wildcard represents indices of the current wrapper array of objects
the demo on the site http://jolt-demo.appspot.com/ is
I have a particular field in my document which has a multilevel nested array structure. The document looks like something this
{
"_id" : ObjectId("62171b4207476091a17f595f"),
"data" : [
{
"id" : "1",
"content" : [
{
"id" : "1.1",
"content" : []
},
{
"id" : "1.2",
"content" : [
{
"id" : "1.2.1",
"content" : [
{
"id" : "1.2.1.1",
"content" : []
}
]
},
{
"id" : "1.2.2",
"content" : []
}
]
}
]
}
]
}
(The ids in my actual data is a random string, I have added a more defined id here just for readability)
In my application code the nesting level is controlled so it won't go more than 5 levels deep.
I need to project a particular object inside one of the deeply nested arrays.
I have all the information needed to traverse the nested structure. For example if I need to fetch the object with id "1.2.2" my input will look something like this:
[{id: 1, index: 0}, {id: 1.2, index: 1}, {id: 1.2.2, index: 1}]
In the above array, each element represents one level of nesting. I have the Id and the index. So in the above example, I know I first need to travel to index 0 at the top level, then inside that to index 1 , then inside that to index 1 again to find my object.
Is there a way I can only get the inner object that I want directly using a query. Or will I need to get the whole "data" field and do the traversal in my application code. I have been unable to figure out any way to construct a query that would satisfy my need.
Query
if you know the path, you can do it using a series of nested
$getField
$arrayElemAt
you can do it in one stage with nested calls, or with many new fields like i did bellow, or with mongodb variables
*i am not sure what output you need, this goes inside to get the 2 using the indexes (if this is not what you need add if you can the expected output)
Test code here
Data
[
{
"_id": ObjectId( "62171b4207476091a17f595f"),
"data": [
{
"id": "1",
"content": [
{
"id": "1.1",
"content": []
},
{
"id": "1.2",
"content": [
{
"id": "1.2.1",
"content": [
{
"id": "1.2.1.1",
"content": []
}
]
},
{
"id": "1.2.2",
"content": [1,2]
}
]
}
]
}
]
}
]
Query
aggregate(
[{"$set":
{"c1":
{"$getField":
{"field":"content", "input":{"$arrayElemAt":["$data", 0]}}}}},
{"$set":
{"c2":
{"$getField":
{"field":"content", "input":{"$arrayElemAt":["$c1", 1]}}}}},
{"$set":
{"c3":
{"$getField":
{"field":"content", "input":{"$arrayElemAt":["$c2", 1]}}}}},
{"$project":{"_id":0, "c4":{"$arrayElemAt":["$c3", 1]}}}])
Results
[{
"c4": 2
}]
I am having trouble with querying a MongoDB collection with an array inside.
Here is the structure of my collection that I am querying. This is one record:
{
"_id": "abc123def4567890",
"profile_id": "abc123def4567890",
"image_count": 2,
"images": [
{
"image_id": "ABC123456789",
"image_url": "images/something.jpg",
"geo_loc": "-0.1234,11.234567890",
"title": "A Title",
"shot_time": "01:23:33",
"shot_date": "11/22/2222",
"shot_type": "scenery",
"conditions": "cloudy",
"iso": 16,
"f": 2.4,
"ss": "1/545",
"focal": 6.0,
"equipment": "",
"instructions": "",
"upload_date": 1234567890,
"update_date": 1234567890
},
{
"image_id": "ABC123456789",
"image_url": "images/something.jpg",
"geo_loc": "-0.1234,11.234567890",
"title": "A Title",
"shot_time": "01:23:33",
"shot_date": "11/22/2222",
"shot_type": "portrait",
"conditions": "cloudy",
"iso": "16",
"f": "2.4",
"ss": "1/545",
"focal": "6.0",
"equipment": "",
"instructions": "",
"upload_date": 1234567890,
"update_date": 1234567890
}
]
}
Forgive the formatting, I didn't know how else to show this.
As you can see, it's a profile with a series of images within an array called 'images' and there are 2 images. Each of the 'images' array items contain an object of attributes for the image (url, title, type, etc).
All I want to do is to return the object element whose attributes match certain criteria:
Select object from images which has shot_type = "scenery"
I tried to make it as simple as possible so i started with:
find( { "images.shot_type": "scenery" } )
This returns the entire record and both the images within. So I tried projection but I could not isolate the single object within the array (in this case object at position 0) and return it.
I think the answer lies with projection but I am unsure.
I have gone through the MongoDB documents for hours now and can't find inspiration. I have read about $elemMatch, $, and the other array operators, nothing seems to allow you to single out an array item based on data within. I have been through this page too https://docs.mongodb.com/manual/tutorial/query-arrays/ Still can't work it out.
Can anyone provide help?
Have I made an error by using '$push' to populate my images field (making it an array) instead of using '$set' which would have made it into an embedded document? Would this have made a difference?
Using aggregation:
db.collection.aggregate({
$project: {
_id: 0,
"result": {
$filter: {
input: "$images",
as: "img",
cond: {
$eq: [
"$$img.shot_type",
"scenery"
]
}
}
}
}
})
Playground
You can use $elemMatch in this way (simplified query):
db.collection.find({
"profile_id": "1",
},
{
"images": {
"$elemMatch": {
"shot_type": 1
}
}
})
You can use two objects into find query. The first will filter all document and will only get those whose profile_id is 1. You can omit this stage and use only { } if you wnat to search into the entire collection.
Then, the other object uses $elemMatch to get only the element whose shot_type is 1.
Check an example here
In Azure search, is it possible to select objects in an array (Collection(Edm.ComplexType) field) which satisfy a predicate?
Using the any operator specified at https://learn.microsoft.com/en-us/azure/search/search-query-understand-collection-filters#correlated-versus-uncorrelated-search returns the entire root object if any of the objects in the array satisfies the predicate.
Example, given the object below in Azure search:
{
"arrayOfObjects": [
{
"id": 1,
"foo": "a"
},
{
"id": 2,
"foo": "b"
},
{
"id": 3,
"foo": "b"
}
]
}
Is it possible to select only the nested objects where foo equals “b”, so that the search response looks like this:
{
"arrayOfObjects": [
{
"id": 2,
"foo": "b"
},
{
"id": 3,
"foo": "b"
}
]
}
No, this is not possible. Queries in Azure Search operate at the granularity of documents, not objects within documents. A possible workaround would be to model your index such that the individual objects become top-level documents.
I am trying to identify documents where both key-value pairs within an array match using the aggregate pipeline. Specifically, if I want to find documents where one array contains user_attribute.Name = Quests_In_Progress and user_attribute.Value =3. Below is an example of such a document that I'm trying to match.
If I use
db.myCollection.aggregate({
$match: {
"user_attribute.Name": "Quests_In_Progress",
"user_attribute.Value": "3"
}
})
It will match every document that contains Quests_In_Progress for user_attribute.Name in one element of the array and contains "3" for user_attribute.Value, regardless of whether they exist in the same element of the array or not.
i.e.
db.myCollection.aggregate({
$match: {
"user_attribute.Name": "Quests_In_Progress",
"user_attribute.Value": "0"
}
})
will match the same document simply because one element of the array has a key:Value pair of Value:0 and another element of the array contains a key:value pair of Quests_In_Progress.
What I want to do is identify documents where both of those conditions are met within one element of the array.
I tried to do this with $elemMatch, but I couldn't get it to work. Plus the aggregate documentation doesn't indicate that $elemMatch works, so maybe that's why I couldn't get it to work.
Lastly, I need to use the aggregate pipeline, because there are a bunch of other things I have to do after finding these documents- specifically unwinding them.
{
"_id": ObjectId("5555bb32de938ce667f78ce00"),
"user_attribute": [{
"Value": "Facebook",
"Name": "Social_Connection"
}, {
"Name": "Total_Fireteam_Missions_Initiated",
"Value": "0"
}, {
"Name": "Quests_Completed",
"Value": "3"
}, {
"Name": "Item_Slots_Owned",
"Value": "36"
}, {
"Name": "Quests_In_Progress",
"Value": "3"
}, {
"Name": "Player_Progression",
"Value": "0"
}, {
"Value": "1",
"Name": "Characters_Owned"
}, {
"Name": "Quests_Started",
"Value": "6"
}, {
"Name": "Total_Friends",
"Value": "0"
}, {
"Name": "Device_Type",
"Value": "Phone"
}]
}
Try using $elemMatch
db.myCollection.aggregate([{$match: {"user_attribute": {$elemMatch: {"Name":"Quests_In_Progress", "Value":"0"}}}}, { $out, "temp"}])
That query will find anyone who has element of their array "Quests_In_Progress" with a value of 0 and put it into the collection temp