so i created a collection called food with 2 objects that were saved no problem. Using find() yielded no issues either. However, when I entered the following:
db.food.find().sort({averageRating:-1}).select({_id: 1}).limit(2)
I get the error:
JS Error: TypeError: Object DBCursor has no method 'sort'
What am i doing wrong?
Is this what you are looking for?
db.food.find({},{_id:1}).sort({"averageRating":-1}).limit(2);
It selects only 2 id fields ordered by average rating descending.The fields that are to be returned are specified by the second parameter in find(),which in this case is _id.
select is not a valid command in mongoDb as far as I know.
It should be selector, not select. See if that fixes it.
As per shargors' comment, it looks like try.mongodb.org doesn't support sort(). I would recommend downloading and installing mongodb itself, and playing around with the real shell.
Related
I want to get a single Observable from a collection, but I want to get it from a different field that is not the id. It is possible?
I do not want to do a query and limit to 1. I need to get a Single Observable not an array Observable.
Schema:
Code:
this.afs.doc<Credit>('credits/uid/'+ uid).valueChanges();
Error:
Invalid document reference. Document references must have an even number of segments, but credits/uid/d1Zt8sozYqb6H27lhoJgF1Gx2Cc2 has 3
I am not sure if I understand correctly, but I guess that you want to get document with particular uid field value, not using document id.
This particular error is related with common feature of Firestore, that every document has to be in collection not in document. So path values for documents, (nested as well) are always checked, if the segments (devided by /) number is even ex. collection1/doc1/collection2/doc2/collection3/doc3
As results in your code we have 3 segments (like credits/uid/<uid_value>) so this is the error.
I am not very familiar with angularFire2 itself, but I have done it in JS. The approach is normally to query collection and than use method on the results, which in classic JS returns Query object on which the same methods can be used as on CollectionReference (which extends 'Query' btw - reference 1).
Combining this approach with those references: querying and collection I propose following solution:
this.afs.collection('credits', ref => ref.where('uid', '==', <uid_value>)).valueChanges()
If uid_value will be unique you should get your doc.
Unfortunately I do not have any playground to test the solution so please let me know how it works - or if there will be any additional errors.
I hope it will help! Good Luck!
I am using Pymongo (v3.5.1) in a Python v3.6.3 Jupyter notebook.
Problem
Even-though I am limiting my results, the db.collection.find() is still retrieving all results before returning
My code:
for post in posts.find({'subreddit_1':"the_donald"}, limit=2):
print(post)
exit
Background
I have imported the Reddit comment data set (RC_2017-01) from files.pushshift.io and created an index on the subreddit field (subreddit_1).
My Indexes
I believe this is caused by the collection having no index on your query term, as exhibited by the line:
planSummary: COLLSCAN
which means that to answer your query, MongoDB is forced to look at each document in the collection one by one.
Creating an index to support your query should help. You can create an index in the mongo shell by executing:
db.posts.createIndex({'subreddit_1': 1})
This is assuming your collection is named posts.
Please note that creating that index would only help with the query you posted. It's likely that different index would be needed for different type of queries.
To read more about how indexing works in MongoDB, check out https://docs.mongodb.com/manual/indexes/
I think you need to change the query, because in find() method 2nd parameter is projection. Find() always return cursor and limit function always works on cursor.
So the syntax should like below:
for post in posts.find({'subreddit_1':"the_donald"})[<start_index>:<end_index>]
print(post)
exit
OR
for post in posts.find({'subreddit_1':"the_donald"}).limit(2)
print(post)
exit
Please read the doc for detail
I am new to Mongo and can't seem to figure out the following after reading posts and the documentation. I am executing the following query:
db.collection.find({'name':'example name'})
Which returns 14 results. I can get the count of correctly by executing:
db.collection.find({'name':'example name'}).count()
However, I want to return the full documents and the count in a single query, similar to the way Elasticsearch does. Is there anyway to do this.
Additionally, is there any equivalence to Elasticsearch's Bool should query (http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-bool-query.html). Essentially I would want to rank the results, so that those with attribute 'onSale=True' are returned before 'onSale=False'.
I'm not sure about your second question, whether MongoDB provides some mechanism equivalent to Elasticsearch's Bool should query.
But for your 1st question, I think you can use Cursor.
var cursor = db.collection.find({'name':'example name'});
Once you've got the cursor, you can use it for getting the count in the following way:
cursor.count()
as well as for getting the documents wrapped in an array in the following way:
cursor.toArray()
For more info on cursor, please see the below mentioned link:
http://docs.mongodb.org/manual/tutorial/iterate-a-cursor/
I know it is probably a simple solution but for some reason I am having trouble calling it... I tried querying it then calling
user.connected_accounts.facebook but that does not work... I need to get hte number out.
Here is the code:
"connected_accounts":[{"facebook":"5555555"}],
Here is my mongoose schema:
connected_accounts: {type: Array}
For you question, I want to know you query clause, in mongodb console, it is different when you are using db.collection.find method and db.collection.findOne method, find method will return an collections, but findOne method will return one object(docment).
So if you are using find, you can get result like: results[0].connected_accounts[0].facebook , if you are using findOne, you can get result like: results.connected_accounts[0].facebook.
I had to just called connected_account[0].facebook to get the value.
Given the Set in my Image Example,
Is it possible to retrieve by ID and if 'element is in the array'?
As you can see I can find all the records with the element in the array, but as I drill down and find the one by ID as well, it throws an Error, I suspect my syntax is wrong
here is a link to my chat on SO https://chat.stackoverflow.com/transcript/message/5006697#5006697
Thanks in Advance
CAM
You basically have the $in in the projection field (what you want to return) because you closed out the criteria document (what you want to find) early. Try this:
db.users.find( {'_id':1, 'companies-visited': { $in:["stocktwits"]}})