I am working with MongoDB and Perl. Here is my data structure:
{
"_id" : ObjectId("501976f8005c8b541d000000"),
"err_id" : "err",
"solution" : [
{
"attachment" : "attach",
"macr" : "macrs",
"yammer" : "yam",
"resolution" : "l",
"salesforce" : "salesforce",
"username" : "bob"
},
{
"attachment" : "attach",
"macr" : "macrs",
"yammer" : "yam",
"resolution" : "losssss",
"salesforce" : "salesforce",
"username" : "bob"
}
]
}
As you can see, I have an array with objects inside. I have created this using the Perl MongoDB library.
I am familiar with some syntax for manipulating arrays in the Perl MongoDB lib. For example, I use this to find entries with a username the same as $username.
$users->find({"solution.username" => $username});
I thought removing an element would be as simple:
$users->remove({"solution.username" => $username});
But alas, it is not so. I have tried this and using pull, but to no avail! I've had a hard time finding this. Does anybody know the syntax to remove an array element based on the contents of one of its fields?
The MongoDB::Collection remove() method will remove documents matched by your query .. so definitely not what you are looking for.
To delete specific fields you should use $unset.
Your solution.usernames are actually in an array, so you would have to include an array index for the fields to delete, eg:
$users->update({"_id" => '123'}, {
'$unset' => {
'solution.0.username' => 1,
'solution.1.username' => 1
}
});
I'm not aware of a shorter syntax to unset all fields matching username within the solution array, but you can add multiple solution.#.username fields to the $unset command.
My example above deletes the first two username entries from the array. If the matching document(s) had more than two username entries, each time you ran this update you would delete up to two more entries (if they exist).
Related
I have lots of documents inside a collection.
The structure of each of the documents inside the collection is as it follows:
{
"_id" : ObjectId(....),
"valor" : {
"AB" : {
"X" : 0.0,
"Y" : 142.6,
},
"FJ" : {
"X" : 0.2,
"Y" : 3.33
....
The collection has currently about 200 documents and I have noticed that one of the keys inside valor has the wrong name. In this case we will say "FJ" shall be "JOF" in all the docs of the collection.
Im pretty sure it is possible to change the key in all the docs using the update function of pymongo. The problem I am facing is that when I visit the online doc available https://docs.mongodb.com/v3.0/reference/method/db.collection.update/ only explains how to change the values(which I would like to remain how they currently are and change only the keys).
This is what I have tried:
def multi_update(spec_key,key_updte):
rdo=col.update((valor.spec_key),{"$set":(valor.key_updte)},multi=True)
return rdo
print(multi_update('FJ','JOF'))
But outputs name 'valor' is not defined . I thought I shall use valor.specific_key to access to the corresponding json
how can I update a key only along the docs of the collection?
You have two problems. First, valor is not an identifier in your Python code, it's a field name of a MongoDB document. You need to quote it in single or double quotes in Python in order to make it a string and use it in a PyMongo update expression.
Your second problem is, MongoDB's update command doesn't allow you set one field to the value of another, nor to rename a field. However, you can reshape all the documents in your collection using the aggregate command with a $project stage and store the results in a second collection using a $out stage.
Here's a complete example to play with:
db = MongoClient().test
collection = db.collection
collection.delete_many({})
collection.insert_one({
"valor" : {
"AB" : {
"X" : 0.0,
"Y" : 142.6,
},
"FJ" : {
"X" : 0.2,
"Y" : 3.33}}})
collection.aggregate([{
"$project": {
"valor": {
"AB": "$valor.AB",
"FOJ": "$valor.FJ"
}
}
}, {
"$out": "collection2"
}])
This is the dangerous part. First, check that "collection2" has all the documents you want, in the desired shape. Then:
collection.drop()
db.collection2.rename("collection")
import pprint
pprint.pprint(collection.find_one())
This is the case: A webshop in which I want to configure which items should be listed in the sjop based on a set of parameters.
I want this to be configurable, because that allows me to experiment with different parameters also change their values easily.
I have a Product collection that I want to query based on multiple parameters.
A couple of these are found here:
within product:
"delivery" : {
"maximum_delivery_days" : 30,
"average_delivery_days" : 10,
"source" : 1,
"filling_rate" : 85,
"stock" : 0
}
but also other parameters exist.
An example of such query to decide whether or not to include a product could be:
"$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);
I'm having a little trouble writing a query that needs to compare a given value against a certain field in all embedded documents within an array. I will give an example to make the issue less abstract.
Let's say I want to use MongoDB to store the last queries that users on my network have entered into different online search engines. An entry in the collection would have a structure like this :
{
'_id' : 'zinfandel',
'last_search' : [
{
'engine' : 'google.com',
'query' : 'why is the sky blue'
},
{
'engine' : 'bing.com',
'query' : 'what is love'
},
{ 'engine' : 'yahoo.com',
'query' : 'how to tie a tie'
}
]
}
Now let's say user username enters a new query into a certain engine. The code that stores this query in the DB needs to find out whether there already exists an entry for the engine that the user used. If yes, this entry is to be updated with the new query. If not, a new entry should be created. My idea is to do a $push only if there is no entry for the given engine and do a $set otherwise. For this purpose, I tried to write my push like this :
db.mycollection.update(
{ '_id' : username , search.$.engine : { '$ne' : engine } },
{ '$push' : { 'search.$.engine' : engine, 'search.$.query' : query } }
)
However, this pushes a new embedded document even if there already was an entry for the given engine. The problem seems to be that the $ne operator doesn't work with arrays like I expect it to work. What I need is a way to make sure that not a single embedded document in the array has an "engine" entry that matches the specified engine.
Does anyone have an idea how to do that? Please tell me if I need to further clarify the question ...
You can push the item into the array with the following command:
db.mycollection.update({
_id: "zinfandel",
"last_search.engine": {
$nin: ["notwellknownengine.com"]
}
}, {
$push: {
"last_search": {
"engine" : "notwellknownengine.com",
"query" : "stackoveflow.com"
}
}
});
It seems that i can go further than one subdocument if i want to add it dynamicaly, here is the code:
db.users.update({"pup.cmn.id":id}, {"$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.