I'm seeing some differences between 2.0.7 and 2.2.0 when it comes to the $elemMatch operation.
In 2.2.0, I do get results back with this query:
db.testColl.find( { "metadata" : {$elemMatch : {$gt : {age:23}, $lt : {age:99}} }});
In 2.0.7, I don't get any results back.
For testing purposes, I have only one document in my testColl collection:
{
"_id" : ObjectId("4fb2974cbedb4a626109b002"),
"metadata" : [
{
"age" : 59
},
{
"gender" : "FEMALE"
}
]
}
Does anyone know why this works in 2.2.0, but not 2.0.7?
According to this:
http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24elemMatch
elemMatch is supported for v1.4+
Thanks,
Galen
If you're looking for a way that works in both versions, you don't need to use $elemMatch here because you're only comparing against a single field so you can use a simpler query. Try this instead:
db.testColl.find({ 'metadata.age': { $gt: 23, $lt: 99 }});
Related
I have this collection in MongoDB that contains the following entries. I'm using Robo3T to run the query.
{
"_id" : ObjectId("xxx1"),
"Evaluation Date" : "2021-09-09",
"Results" : [
{
"Name" : "ABCD",
"Version" : "3.2.x"
}
]
"_id" : ObjectId("xxx2"),
"Evaluation Date" : "2022-09-09",
"Results" : [
{
"Name" : "ABxD",
"Version" : "5.2.x"
}
]
}
This document contains multiple entries of similar format. Now, I need to extract the latest value for "Version".
Expected output:
5.2.x
Measures I've taken so far:
(1) I've only tried findOne() and while I was able to extract the value of "Version": db.getCollection('TestCollectionName').findOne().Results[0].Version
...only the oldest entry was returned.
3.2.x
(2) Using the find().sort().limit() like below, returns the entire document for the latest entry and not just the data value that I wanted; db.getCollection('TestCollectionName').find({}).sort({"Results.Version":-1}).limit(1)
Results below:
"_id" : ObjectId("xxx2"),
"Evaluation Date" : "2022-09-09",
"Results" : [
{
"Name" : "ABxD",
"Version" : "5.2.x"
}
]
(3) I've tried to use sort() and limit() alongside findOne() but I've read that findOne is maybe deprecated and also not compatible with sort. And thus, resulting to an error.
(4) Finally, if I try to use sort and limit on find like this: db.getCollection('LD_exit_Evaluation_Result_MFC525').find({"Results.New"}).sort({_id:-1}).limit(1) I would get an unexpected token error.
What would be a good measure for this?
Did I simply mistake to/remove a bracket or need to reorder the syntax?
Thanks in advance.
I'm not sure if I understood well, but maybe this could be what are you looking for:
db.collection.aggregate([
{
"$project": {
lastResult: {
"$last": "$Results"
},
},
},
{
"$project": {
version: "$lastResult.Version",
_id: 0
}
}
])
It uses aggregate with some operators: the first $project calculate a new field called lastResult with the last element of each array using $last operator. The second $project is just to clean the output. If you need the _id reference, just remove _id: 0 or change its value to 1.
You can check how it works here: https://mongoplayground.net/p/jwqulFtCh6b
Hope I helped
Suppose, we have this type of documents :
{
"_id" : ObjectId("4c02c58de500fe1be1000305"),
"date" : ""20090530"
}
{
"_id" : ObjectId("4c02c58de500fe1be1000005"),
"date" : ""20090607"
}
Is it possible to find/group all documents with 7 days between them?
With aggregate?
You can write something like this, I believe you won't be needing aggregation here, if you are doing this for the same collection:
db.collectionName.find({date: { $gte: "20090530", $lte: "20090607" } } );
Reference: $lte and $gte
I did this in my mongodb:
db.teams.insert({name:"Alpha team",employees:[{name:"john"},{name:"david"}]});
db.teams.insert({name:"True team",employees:[{name:"oliver"},{name:"sam"}]});
db.teams.insert({name:"Blue team",employees:[{name:"jane"},{name:"raji"}]});
db.teams.find({"employees.name":/.*o.*/});
But what I got was:
{ "_id" : ObjectId("5ddf3ca83c182cc5354a15dd"), "name" : "Alpha team", "employees" : [ { "name" : "john" }, { "name" : "david" } ] }
{ "_id" : ObjectId("5ddf3ca93c182cc5354a15de"), "name" : "True team", "employees" : [ { "name" : "oliver" }, { "name" : "sam" } ] }
But what I really want is
[{"name":"john"},{"name":"oliver"}]
I'm having a hard time finding examples of this without using some kind of programmatic iterator/loop. Or examples I find return the parent document, which means I'd have to parse out the embedded array employees and do some kind of UNION statement?
Eg.
How to get embedded document in mongodb?
Retrieve only the queried element in an object array in MongoDB collection
Can someone point me in the right direction?
Please add projections to filter out the fields you don't need. Please refer the project link mongodb projections
Your find query should be constructed with the projection parameters like below:
db.teams.find({"employees.name":/.*o.*/}, {_id:0, "employees.name": 1});
This will return you:
[{"name":"john"},{"name":"oliver"}]
Can be solved with a simple aggregation pipeline.
db.teams.aggregate([
{$unwind : "$employees"},
{$match : {"employees.name":/.*o.*/}},
])
EDIT:
OP Wants to skip the parent fields. Modified query:
db.teams.aggregate([
{$unwind : "$employees"},
{$match : {"employees.name":/.*o.*/}},
{$project : {"name":"$employees.name",_id:0}}
])
Output:
{ "name" : "john" }
{ "name" : "oliver" }
I have the following documents,
{
"_id" : ObjectId("5b85312981c1634f59751604"),
"date" : "0"
},
{
"_id" : ObjectId("5b85312981c1634f59751604"),
"date" : "20180330"
},
{
"_id" : ObjectId("5b85312981c1634f59751604"),
"date" : "20180402"
},
{
"_id" : ObjectId("5b85312981c1634f59751604"),
"date" : "20180323"
},
I tried to convert date to ISODate using $toDate in aggregation,
db.documents.aggregate( [ { "$addFields": { "received_date": { "$cond": [ {"$ne": ["$date", "0"] }, {"$toDate": "$date"}, new Date("1970-01-01") ] } } } ] )
the query executed fine, but when I
db.documents.find({})
to examine all the documents, nothing changed, I am wondering how to fix it. I am using MongoDB 4.0.6 on Linux Mint 19.1 X64.
As they mentioned in the comments, aggregate doesn't update documents in the database directly (just an output of them).
If you'd like to permanently add a new field to documents via aggregation (aka update the documents in the database), use the following .forEach/.updateOne method:
Your example:
db.documents
.aggregate([{"$addFields":{"received_date":{"$cond":[{"$ne":["$date","0"]}, {"$toDate": "$date"}, new Date("1970-01-01")]}}}])
.forEach(function (x){db.documents.updateOne({_id: x._id}, {$set: {"received_date": x.received_date}})})
Since _id's value is an ObjectID(), there may be a slight modification you need to do to {_id:x._id}. If there is, let me know and I'll update it!
Another example:
db.users.find().pretty()
{ "_id" : ObjectId("5acb81b53306361018814849"), "name" : "A", "age" : 1 }
{ "_id" : ObjectId("5acb81b5330636101881484a"), "name" : "B", "age" : 2 }
{ "_id" : ObjectId("5acb81b5330636101881484b"), "name" : "C", "age" : 3 }
db.users
.aggregate([{$addFields:{totalAge:{$sum:"$age"}}}])
.forEach(function (x){db.users.updateOne({name: x.name}, {$set: {totalAge: x.totalAge}})})
Being able to update collections via the aggregation pipeline seems to be quite valuable because of what you have the power to do with aggregation (e.g. what you did in your question, doing calculations based on other fields within the document, etc.). I'm newer to MongoDB so maybe updating collections via aggregation pipeline is "bad practice", but it works and it's been quite valuable for me. I wonder why it isn't more straight-forward to do?
Note: I came up with this method after discovering Nazo's now-deprecated .save() method. Shoutout to Nazo!
I've recently updated to Mongodb 2.2.0 and found that the following query now no longer works.
The database is empty and I run the following:
db.Sessions.update({_id:"test",sessions:{$not:{$elemMatch:{type:"Web"}}}},{$push:{sessions:{type:"Web",dateAdded:new Date}}},true)
returns the error:
Cannot apply $push/$pushAll modifier to non-array
Prior to the update the following document would have been created:
{ "_id" : "test", "sessions" : [ { "type" : "Web", "dateAdded" : ISODate("2012-09-12T15:11:11.942Z") } ] }
Any ideas?
Edit:
I forgot to mention, it's the addition of the $not that breaks in this version as the following works fine, so it's not a issue that the array/field doesn't exist.
db.Sessions.update({_id:"test"},{$push:{sessions:{type:"Web",dateAdded:new Date}}},true)
The behavior of $elemMatch has changed slightly in 2.2, which is why this no longer works in combination with $not, which is only a meta-operator for negating other operators and can not actually be used to search fields.
Instead, you can use $nin (not in) to inspect the values inside your sessions array.
For example,
> db.Sessions.update( { _id:"test", sessions: { "$nin": {type: "Web"} } }, {"$push":{sessions:{type:"Web",dateAdded:new Date}}},true);
> db.Sessions.findOne();
{
"_id" : "test",
"sessions" : [
{
"type" : "Web",
"dateAdded" : ISODate("2012-09-12T16:03:18.271Z")
}
]
}
I filed a bug "a query field with a $not operator should not be used to populate an upsert document" which will be backported into 2.2.x that fixes this situation.