I'm following this tutorial in creating mongo views
https://www.percona.com/blog/2017/01/13/mongodb-3-4-views/
The issue here is when i run the command
db.createView('employee_names','employee', [{ $project : { _id : 0, "fullname" : {$concat : ["$FirstName", " ", "$LastName"]}}}])
I get an error saying createView is not a function
My mongo version is 3.4. What am i missing .
Views work in MongoDb since version 3.4, so instead of RoboMongo one might need Robo 3T. And of course this will work is shell as well. (Assuming old installations are upgraded to 3.4 as described at https://docs.mongodb.com/master/release-notes/3.4/#upgrade.)
//There are two collection state and City I would Like to create view on them
db.createView(
... "statedistrict", //View Name
... "States", //First Collection Name
... [
... {$lookup:{from:"Districts",localField:"StateId",foreignField:"StateId", as:"trial"}},
... {$project:{"_id":0,"StateId":1,"StateName":1,"trial.DistrictName":1}}
... ]
... )
//After Pressing Enter You Will get below ok message.
{ "ok" : 1 }
//Then pass the below command to see the result/record
db.statedist.find().pretty()
0 means - don't display
1 means - display
From 1st collection I need all to display except _id. So, only _id is kept 0
From 2nd collection I don't need many. So, I have used trial.not_required_field_name : 0 (you can use any name instead of trial)
Related
This is the case: A webshop in which I want to configure which items should be listed in the sjop based on a set of parameters.
I want this to be configurable, because that allows me to experiment with different parameters also change their values easily.
I have a Product collection that I want to query based on multiple parameters.
A couple of these are found here:
within product:
"delivery" : {
"maximum_delivery_days" : 30,
"average_delivery_days" : 10,
"source" : 1,
"filling_rate" : 85,
"stock" : 0
}
but also other parameters exist.
An example of such query to decide whether or not to include a product could be:
"$or" : [
{
"delivery.stock" : 1
},
{
"$or" : [
{
"$and" : [
{
"delivery.maximum_delivery_days" : {
"$lt" : 60
}
},
{
"delivery.filling_rate" : {
"$gt" : 90
}
}
]
},
{
"$and" : [
{
"delivery.maximum_delivery_days" : {
"$lt" : 40
}
},
{
"delivery.filling_rate" : {
"$gt" : 80
}
}
]
},
{
"$and" : [
{
"delivery.delivery_days" : {
"$lt" : 25
}
},
{
"delivery.filling_rate" : {
"$gt" : 70
}
}
]
}
]
}
]
Now to make this configurable, I need to be able to handle boolean logic, parameters and values.
So, I got the idea, since such query itself is JSON, to store it in Mongo and have my Java app retrieve it.
Next thing is using it in the filter (e.g. find, or whatever) and work on the corresponding selection of products.
The advantage of this approach is that I can actually analyse the data and the effectiveness of the query outside of my program.
I would store it by name in the database. E.g.
{
"name": "query1",
"query": { the thing printed above starting with "$or"... }
}
using:
db.queries.insert({
"name" : "query1",
"query": { the thing printed above starting with "$or"... }
})
Which results in:
2016-03-27T14:43:37.265+0200 E QUERY Error: field names cannot start with $ [$or]
at Error (<anonymous>)
at DBCollection._validateForStorage (src/mongo/shell/collection.js:161:19)
at DBCollection._validateForStorage (src/mongo/shell/collection.js:165:18)
at insert (src/mongo/shell/bulk_api.js:646:20)
at DBCollection.insert (src/mongo/shell/collection.js:243:18)
at (shell):1:12 at src/mongo/shell/collection.js:161
But I CAN STORE it using Robomongo, but not always. Obviously I am doing something wrong. But I have NO IDEA what it is.
If it fails, and I create a brand new collection and try again, it succeeds. Weird stuff that goes beyond what I can comprehend.
But when I try updating values in the "query", changes are not going through. Never. Not even sometimes.
I can however create a new object and discard the previous one. So, the workaround is there.
db.queries.update(
{"name": "query1"},
{"$set": {
... update goes here ...
}
}
)
doing this results in:
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"nModified" : 0,
"writeError" : {
"code" : 52,
"errmsg" : "The dollar ($) prefixed field '$or' in 'action.$or' is not valid for storage."
}
})
seems pretty close to the other message above.
Needles to say, I am pretty clueless about what is going on here, so I hope some of the wizzards here are able to shed some light on the matter
I think the error message contains the important info you need to consider:
QUERY Error: field names cannot start with $
Since you are trying to store a query (or part of one) in a document, you'll end up with attribute names that contain mongo operator keywords (such as $or, $ne, $gt). The mongo documentation actually references this exact scenario - emphasis added
Field names cannot contain dots (i.e. .) or null characters, and they must not start with a dollar sign (i.e. $)...
I wouldn't trust 3rd party applications such as Robomongo in these instances. I suggest debugging/testing this issue directly in the mongo shell.
My suggestion would be to store an escaped version of the query in your document as to not interfere with reserved operator keywords. You can use the available JSON.stringify(my_obj); to encode your partial query into a string and then parse/decode it when you choose to retrieve it later on: JSON.parse(escaped_query_string_from_db)
Your approach of storing the query as a JSON object in MongoDB is not viable.
You could potentially store your query logic and fields in MongoDB, but you have to have an external app build the query with the proper MongoDB syntax.
MongoDB queries contain operators, and some of those have special characters in them.
There are rules for mongoDB filed names. These rules do not allow for special characters.
Look here: https://docs.mongodb.org/manual/reference/limits/#Restrictions-on-Field-Names
The probable reason you can sometimes successfully create the doc using Robomongo is because Robomongo is transforming your query into a string and properly escaping the special characters as it sends it to MongoDB.
This also explains why your attempt to update them never works. You tried to create a document, but instead created something that is a string object, so your update conditions are probably not retrieving any docs.
I see two problems with your approach.
In following query
db.queries.insert({
"name" : "query1",
"query": { the thing printed above starting with "$or"... }
})
a valid JSON expects key, value pair. here in "query" you are storing an object without a key. You have two options. either store query as text or create another key inside curly braces.
Second problem is, you are storing query values without wrapping in quotes. All string values must be wrapped in quotes.
so your final document should appear as
db.queries.insert({
"name" : "query1",
"query": 'the thing printed above starting with "$or"... '
})
Now try, it should work.
Obviously my attempt to store a query in mongo the way I did was foolish as became clear from the answers from both #bigdatakid and #lix. So what I finally did was this: I altered the naming of the fields to comply to the mongo requirements.
E.g. instead of $or I used _$or etc. and instead of using a . inside the name I used a #. Both of which I am replacing in my Java code.
This way I can still easily try and test the queries outside of my program. In my Java program I just change the names and use the query. Using just 2 lines of code. It simply works now. Thanks guys for the suggestions you made.
String documentAsString = query.toJson().replaceAll("_\\$", "\\$").replaceAll("#", ".");
Object q = JSON.parse(documentAsString);
2 days old to Mongo, so bear with me.
I have a collection from which, I only want to retrieve specific values contingent to another key existing in the MongoDB environment.
Here is what I am doing:
db.results.find({'someKeyThatShouldExist':{$exists:true}}, {"parentKey.childKey.theKeyWoseValueIwant":1}
This yields data in the following format for me:
{ "_id" : ObjectId("532a2c2b6803fa486b8b456a"), "parentKey" : { "childKey" : { "theKeyWhoseValueIWant" : 102982577 }}}.....
Now, all I really want is the value 102982577, not everything else.
How can I do this ?
You can suppress the _id by adding _id:0 to the projection criteria.
db.results.find(
{"someKeyThatShouldExist":{$exists:true}},
{_id:0, "parentKey.childKey.theKeyWoseValueIwant":1}
)
To get just the value, you could do something like:
db.results.find(
{"someKeyThatShouldExist":{$exists:true}},
{_id:0, "parentKey.childKey.theKeyWoseValueIwant":1}
)[0].parentKey.childKey.theKeyWoseValueIwant
It seems that i can go further than one subdocument if i want to add it dynamicaly, here is the code:
db.users.update({"pup.cmn.id":id}, {"$addToSet":{"pup.cmn":{"abus":email}}})
this give error:
OperationFailure: can't append to array using string field name: cmn
then, if i add positional element i get this:
db.users.update({"pup.cmn.id":id}, {"$addToSet":{"pup.$.cmn":{"abus":email}}})
"cmn" :
[
{
"fto" : ObjectId("5190e8a53a5f3a0c102af045")
"id" : "14.05.2013 12:29:53"
},
{
"abus" : "u...#example.com"
}
]
so as you can see, it will add it in the same level, and i dont want that, because the application will get errors.
It seems that Mongodb for the time of writing (2.4.x) have not this feature, there is a ticket:
https://jira.mongodb.org/browse/SERVER-831
I need help incrementing value of all keys in participants without having to know name of the keys inside of it.
> db.conversations.findOne()
{
"_id" : ObjectId("4faf74b238ba278704000000"),
"participants" : {
"4f81eab338ba27c011000001" : NumberLong(2),
"4f78497938ba27bf11000002" : NumberLong(2)
}
}
I've tried with something like
$mongodb->conversations->update(array('_id' => new \MongoId($objectId)), array('$inc' => array('participants' => 1)));
to no avail...
You need to redesign your schema. It is never a good idea to have "random key names". Even though MongoDB is schemaless, it still means you need to have defined key names. You should change your schema to:
{
"_id" : ObjectId("4faf74b238ba278704000000"),
"participants" : [
{ _id: "4f81eab338ba27c011000001", count: NumberLong(2) },
{ _id: "4f78497938ba27bf11000002", count: NumberLong(2) }
]
}
Sadly, even with that, you can't update all embedded counts in one command. There is currently an open feature request for that: https://jira.mongodb.org/browse/SERVER-1243
In order to still update everything, you should:
query the document
update all the counts on the client side
store the document again
In order to prevent race conditions with that, have a look at "Compare and Swap" and following paragraphs.
It is not possible to update all nested elements in one single move in current version of MongoDB. So I can advice to use "foreach {}".
Read realted topic: How to Update Multiple Array Elements in mongodb
I hope this feature will be implemented in next version.
I am trying to update the following document in Mongodb.
doc = { id : 10 , graph :[{userId:1,children:[2]},{userId:2,children:[]}]}
db.test.insert(doc)
then I perform two updates:
db.test.update( {'id':10,'graph.userId' : 1}, { $push:{'graph.$.children':10}})
db.test.update( {'id':10,'graph.userId' : 1},{ $push:{'graph':{'userId':10,'children':[]}}})
(Saddly :
db.test.update( {'id':10,'graph.userId' : 1},{ $push:{'graph.$.children':10},$push:{'graph':{'userId':10,'children':[]}}})
does not work)
Is there a way to update these simultaneously ?
Thanks a lot
You can bundle multiple update operations together, but the only issue with what you've written in pseudo code is that the elements you're pushing belong to different arrays (graph and graph.children respectively.) This needs to be done in two pushes.
Try this:
db.test.update( { id:10, 'graph.userId':1 },
{ $push:{'graph.$.children' : 4 }, $push:{'graph' : {'userId':4,'children':[]}} } )
The multiple keys in the modifier array stop it from working. You have to do two updates to do this if I read your shema right cos you are trying to push a new child onto the current position and push a new record into the subdocument of the parent.
The thing that stops it is the children[] setting. Mongo just does not know where to set that.
I suppose you could try:
db.test.update( {'id':10,'graph.userId' : 1},{ $push:{'graph.$.children':10},$pushAll:{'graph':{{'userId':10,'children':[]}}}})
But it is a long shot