I have searched here but could not find an clear answer to the following question. In the sample collection mycollection below, how would one select distinct vin numbers only in Objects where the status field exists and the status is UNLOCKED ?
I have tried
db.getCollection('mycollection').distinct("vin", {$and: [{"decoded_payload.status": {$exists: true}}, {"decoded_payload.status":"UNLOCKED"}]})
but this query hangs indefinitely
Due to the large size of the database and the lengthy delay of such a query, I would like to limit the output to check if it runs at all but it seems limit() is not an option with .distinct()
In MongoDB, how would one select the distinct vin in the data below, set the limit = 1 and only select based on the status condition (status exists and is equal to "UNLOCKED")?
Would aggregate() be the right choice? How does one use the above conditions with aggregate() and limit() ?
The output in this case would be 34567
{
"_id" : ObjectId("1"),
"vin" : "12345",
"class_name" : "foo",
"decoded_payload" : {
"timestamp" : 1547329250,
"status" : "LOCKED"
}
}
{
"_id" : ObjectId("2"),
"vin" : "23456",
"class_name" : "foo",
"decoded_payload" : {
"timestamp" : 1547329260,
"status" : "LOCKED"
}
}
{
"_id" : ObjectId("3"),
"vin" : "34567",
"class_name" : "bar",
"decoded_payload" : {
"timestamp" : 1547329270,
"status" : "UNLOCKED",
"reservation_id" : "71"
}
}
{
"_id" : ObjectId("4"),
"vin" : "45678",
"class_name" : "baz",
"decoded_payload" : {
"timestamp" : 1547329280,
"reservation_id" : "71"
}
}
You can use this aggregation Query to filter data and return distinct "vin"
db.mycollection.aggregate([
{
$match: {
$and: [{
"decoded_payload.status": { $exists: true }
}, {
"decoded_payload.status": "UNLOCKED"
}]
}
},
{ $limit : 5 }, // You can use this stage after group too
{
$group: { _id: "$vin" }
}
])
Use limit stage before and after $group stage as per requirement
Related
Can't we pass an object to $size operator in mongoose? Is there any ways to query on array for length so we can fetch document which contains an array of a particular length.
Hers is Sample Document
"_id" : ObjectId("5e8c9becd1257f66c4b8cd63"),
"index" : 0,
"name" : "Aurelia Gonzales",
"isActive" : false,
"registered" : ISODate("2015-02-11T09:52:39.000+05:30"),
"age" : 20,
"gender" : "female",
"eyeColor" : "green",
"favoriteFruit" : "banana",
"company" : {
"title" : "YURTURE",
"email" : "aureliagonzales#yurture.com",
"phone" : "+1 (940) 501-3963",
"location" : {
"country" : "USA",
"address" : "694 Hewes Street"
}
},
"tags" : [
"enim",
"id",
"velit",
"ad",
"consequat"
]
}
Here is query
db.admin.aggregate([
{
$match : {tags : {$size : {$lte : 5}}}
}
])
Here is Output
{
"message" : "$size needs a number",
"ok" : 0,
"code" : 2,
"codeName" : "BadValue",
"name" : "MongoError"
}
You can't use $size like that & needed to use aggregation $size operator to do this.
Query :
db.collection.find({
$expr: { /** Allows the use of aggregation expressions within the query language */
$lte: [
{
$size: "$tags"
},
5
]
}
})
Test : MongoDB-Playground
Although if the size of the array is important enough, it could be stored in the documents and indexed to fetch much faster results.
Following a similar logic a solution could be, two stage aggregation using $addFields and $size, $lte.
db.collection.aggregate([
{
$addFields: {
sizeOfTags: {
$size: "$tags"
}
}
},
{
$match: {
sizeOfTags: {
$lte: 5
}
}
}
])
I have collection in which documents are like:
{
_id: ObjectId(),
user: ObjectId(),
studentName: String,
createdAt: Date,
isAbondoned: boolean
}
example of documents are:
1-
{
"_id" : ObjectId("56cd2d36a489a5b875902f0e"),
"user" : ObjectId("56c4cafabd5f92cd78ae49d4"),
"studentName" : "Aman",
"createdAt" : ISODate("2016-02-24T04:10:30.486+0000"),
"isAbandoned" : true
}
2-
{
"_id" : ObjectId("56cd2dcda489a5b875902fcd"),
"user" : ObjectId("56c4cafabd5f92cd78ae49d4"),
"studentName" : "Aman",
"createdAt" : ISODate("2016-02-24T04:13:01.932+0000"),
"isAbandoned" : false
}
3-
{
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281+0000"),
"isAbandoned" : true,
}
Now I want to find the list of students for which their 'isAbandoned' is true for their last 'createdAt' document.
Required output for above example is:
{
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev"
}
because for studentName "Aman" max(createdAt) is 2nd document and 'isAbandoned' is false for that.
The best way to do this is using the aggregation framework. You need to $group your documents by "user" and return the last document for each user using the $last accumulator operator but for this to work, you need a preliminary sorting stage using the $sort aggregation pipeline operator. To sort your documents, you need to consider both the "createdAt" field and the "user" field.
The last stage in the pipeline is the $match stage where you select only those last documents where "isAbandoned" equals true.
db.students.aggregate([
{ "$sort": { "user": 1, "createdAt": 1 } },
{ "$group": {
"_id": "$user",
"last": { "$last": "$$ROOT" }
}},
{ "$match": { "last.isAbandoned": true } }
])
which returns something like this:
{
"_id" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"last" : {
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281Z"),
"isAbandoned" : true
}
}
To get the expected result, we need to use the $replaceRoot pipeline operator starting from verion 3.4 to promote the embedded document to the top level
{
$replaceRoot: { newRoot: "$last" }
}
In older version, you need to use the $project aggregation pipeline operation to reshape our documents. So if we extend our pipeline with the following stage:
{
"$project": {
"_id": "$last._id",
"user": "$last.user",
"studentName": "$last.studentName",
"createdAt": "$last.createdAt",
"isAbandoned": "$last.isAbandoned"
}}
it produces the expected output:
{
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281Z"),
"isAbandoned" : true
}
This is a good example of need to group data by specific filed (createdAt) and then compare result set match criteria.
find max by student id,
match only entries by max entry = createdAt
check if they are passing criteria
reshape document
Code:
db.student.aggregate([{
$group : {
_id : "$user",
created : {
$max : "$createdAt"
},
documents : {
$push : "$$ROOT"
}
}
}, {
$project : {
_id : 0,
documents : {
$filter : {
input : "$documents",
as : "item",
cond : {
$eq : ["$$item.createdAt", "$created"]
}
}
}}
}, {
$match : {
"documents.isAbandoned" : true
}},
{ $unwind : "$documents" },
{
$project : {
_id : "$documents._id",
user : "$documents.user",
studentName : "$documents.studentName",
createdAt : "$documents.createdAt",
isAbandoned : "$documents.isAbandoned",
}}
])
I have collection in which documents are like:
{
_id: ObjectId(),
user: ObjectId(),
studentName: String,
createdAt: Date,
isAbondoned: boolean
}
example of documents are:
1-
{
"_id" : ObjectId("56cd2d36a489a5b875902f0e"),
"user" : ObjectId("56c4cafabd5f92cd78ae49d4"),
"studentName" : "Aman",
"createdAt" : ISODate("2016-02-24T04:10:30.486+0000"),
"isAbandoned" : true
}
2-
{
"_id" : ObjectId("56cd2dcda489a5b875902fcd"),
"user" : ObjectId("56c4cafabd5f92cd78ae49d4"),
"studentName" : "Aman",
"createdAt" : ISODate("2016-02-24T04:13:01.932+0000"),
"isAbandoned" : false
}
3-
{
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281+0000"),
"isAbandoned" : true,
}
Now I want to find the list of students for which their 'isAbandoned' is true for their last 'createdAt' document.
Required output for above example is:
{
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev"
}
because for studentName "Aman" max(createdAt) is 2nd document and 'isAbandoned' is false for that.
The best way to do this is using the aggregation framework. You need to $group your documents by "user" and return the last document for each user using the $last accumulator operator but for this to work, you need a preliminary sorting stage using the $sort aggregation pipeline operator. To sort your documents, you need to consider both the "createdAt" field and the "user" field.
The last stage in the pipeline is the $match stage where you select only those last documents where "isAbandoned" equals true.
db.students.aggregate([
{ "$sort": { "user": 1, "createdAt": 1 } },
{ "$group": {
"_id": "$user",
"last": { "$last": "$$ROOT" }
}},
{ "$match": { "last.isAbandoned": true } }
])
which returns something like this:
{
"_id" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"last" : {
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281Z"),
"isAbandoned" : true
}
}
To get the expected result, we need to use the $replaceRoot pipeline operator starting from verion 3.4 to promote the embedded document to the top level
{
$replaceRoot: { newRoot: "$last" }
}
In older version, you need to use the $project aggregation pipeline operation to reshape our documents. So if we extend our pipeline with the following stage:
{
"$project": {
"_id": "$last._id",
"user": "$last.user",
"studentName": "$last.studentName",
"createdAt": "$last.createdAt",
"isAbandoned": "$last.isAbandoned"
}}
it produces the expected output:
{
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281Z"),
"isAbandoned" : true
}
This is a good example of need to group data by specific filed (createdAt) and then compare result set match criteria.
find max by student id,
match only entries by max entry = createdAt
check if they are passing criteria
reshape document
Code:
db.student.aggregate([{
$group : {
_id : "$user",
created : {
$max : "$createdAt"
},
documents : {
$push : "$$ROOT"
}
}
}, {
$project : {
_id : 0,
documents : {
$filter : {
input : "$documents",
as : "item",
cond : {
$eq : ["$$item.createdAt", "$created"]
}
}
}}
}, {
$match : {
"documents.isAbandoned" : true
}},
{ $unwind : "$documents" },
{
$project : {
_id : "$documents._id",
user : "$documents.user",
studentName : "$documents.studentName",
createdAt : "$documents.createdAt",
isAbandoned : "$documents.isAbandoned",
}}
])
I have collection in which documents are like:
{
_id: ObjectId(),
user: ObjectId(),
studentName: String,
createdAt: Date,
isAbondoned: boolean
}
example of documents are:
1-
{
"_id" : ObjectId("56cd2d36a489a5b875902f0e"),
"user" : ObjectId("56c4cafabd5f92cd78ae49d4"),
"studentName" : "Aman",
"createdAt" : ISODate("2016-02-24T04:10:30.486+0000"),
"isAbandoned" : true
}
2-
{
"_id" : ObjectId("56cd2dcda489a5b875902fcd"),
"user" : ObjectId("56c4cafabd5f92cd78ae49d4"),
"studentName" : "Aman",
"createdAt" : ISODate("2016-02-24T04:13:01.932+0000"),
"isAbandoned" : false
}
3-
{
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281+0000"),
"isAbandoned" : true,
}
Now I want to find the list of students for which their 'isAbandoned' is true for their last 'createdAt' document.
Required output for above example is:
{
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev"
}
because for studentName "Aman" max(createdAt) is 2nd document and 'isAbandoned' is false for that.
The best way to do this is using the aggregation framework. You need to $group your documents by "user" and return the last document for each user using the $last accumulator operator but for this to work, you need a preliminary sorting stage using the $sort aggregation pipeline operator. To sort your documents, you need to consider both the "createdAt" field and the "user" field.
The last stage in the pipeline is the $match stage where you select only those last documents where "isAbandoned" equals true.
db.students.aggregate([
{ "$sort": { "user": 1, "createdAt": 1 } },
{ "$group": {
"_id": "$user",
"last": { "$last": "$$ROOT" }
}},
{ "$match": { "last.isAbandoned": true } }
])
which returns something like this:
{
"_id" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"last" : {
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281Z"),
"isAbandoned" : true
}
}
To get the expected result, we need to use the $replaceRoot pipeline operator starting from verion 3.4 to promote the embedded document to the top level
{
$replaceRoot: { newRoot: "$last" }
}
In older version, you need to use the $project aggregation pipeline operation to reshape our documents. So if we extend our pipeline with the following stage:
{
"$project": {
"_id": "$last._id",
"user": "$last.user",
"studentName": "$last.studentName",
"createdAt": "$last.createdAt",
"isAbandoned": "$last.isAbandoned"
}}
it produces the expected output:
{
"_id" : ObjectId("56cee51503b7cb7b0eda9c4c"),
"user" : ObjectId("56c85244bd5f92cd78ae4bc1"),
"studentName" : "Rajeev",
"createdAt" : ISODate("2016-02-25T11:27:17.281Z"),
"isAbandoned" : true
}
This is a good example of need to group data by specific filed (createdAt) and then compare result set match criteria.
find max by student id,
match only entries by max entry = createdAt
check if they are passing criteria
reshape document
Code:
db.student.aggregate([{
$group : {
_id : "$user",
created : {
$max : "$createdAt"
},
documents : {
$push : "$$ROOT"
}
}
}, {
$project : {
_id : 0,
documents : {
$filter : {
input : "$documents",
as : "item",
cond : {
$eq : ["$$item.createdAt", "$created"]
}
}
}}
}, {
$match : {
"documents.isAbandoned" : true
}},
{ $unwind : "$documents" },
{
$project : {
_id : "$documents._id",
user : "$documents.user",
studentName : "$documents.studentName",
createdAt : "$documents.createdAt",
isAbandoned : "$documents.isAbandoned",
}}
])
{
"_id" : ObjectId("53692eb238ed04c824679f18"),
"firstUserId" : 1,
"secondUserId" : 17,
"messages" : [
{
"_id" : ObjectId("5369338997b964b81d579fc6"),
"read" : true,
"dateTime" : 1399403401,
"message" : "d",
"userId" : 1
},
{
"_id" : ObjectId("536933c797b964b81d579fc7"),
"read" : false,
"dateTime" : 1399403463,
"message" : "asdf",
"userId" : 17
}
]
}
I'm trying to select all documents that have firstUserId = 1 and also have sub documents
that have userId differnet ($ne) to 1 and read = false.
I tried:
db.usermessages.find({firstUserId: 1, "messages.userId": {$ne: 1}, "messages.read": false})
But it returns empty cause messages have both 1 and 17.
And also how to count subdocuments that have given case?
Are you trying to get the count of all the documents which are returned after your match criteria? If Yes, then you might consider using aggregation framework. http://docs.mongodb.org/manual/aggregation/
Something like below could be done to get you the counts:
db.usermessages.aggregate(
{ "$unwind": "$messages" },
{ "$match":
{ "firstUserId": 1,
"messages.userId": { "$ne" : 1},
"messages.read": false
}
},
{ "$group": { "_id" :null, "count" : { "$sum": 1 } } }
)
Hope this helps.
PS: I have not tried this on my system.