I am doing a Mini project in MongoDB recently. I am trying to find out the distinct values of field using the db.collections.distinct(<field>)command.
The above command retrieves all the distinct values of the given field inside an array. But as I have 12k documents all the values are not getting displayed in my console.
This is the output I get.. how to view the entire result?
I have search the internet and documentation but I was not able to get a proper answer.
The mongosh is a Node.js environment. There are several solutions, e.g. JSON.stringify the array or use util.inspect.
JSON.stringify(db.collections.distinct(<field>))
util.inspect(db.collections.distinct(<field>), { maxArrayLength: null })
Related
I'm currently trying to use MongoDB Compass to query my collection. However, I seem to be only able to filter the data.
Is there any way for me to sort the data as well? I would like to sort my data in ascending order using one of my data fields.
If MongoDB Compass isn't the best way to order a collection, what other GUI could I use?
Using MongoDB Compass 1.7 or newer, you can sort (and project, skip, or limit) results by choosing the Documents tab and expanding the Options.
To sort in ascending order by a field myField, use { myField:1 }. Any of the usual cursor sort() options can be provided, including ordering results by multiple fields.
Note: options like sort and skip are not available in the default Schema tab because this view uses sampling to find a random set of documents, as opposed to the Documents view which displays a specific query result.
I am using PyMongo and trying to iterate over (10 millions) documents in my MongoDB collection and just extract a couple of keys: "name" and "address", then output them to .csv file.
I cannot figure out the right syntax to do it with find().forEach()
I was trying workarounds like
cursor = db.myCollection.find({"name": {$regex: REGEX}})
where REGEX would match everything - and it resulted in "Killed".
I also tried
cursor = db.myCollection.find({"name": {"$exist": True}})
but that did not work either.
Any suggestions?
I cannot figure out the right syntax to do it with find().forEach()
cursor.forEach() is not available for Python, it's a JavaScript function. You would have to get a cursor and iterate over it. See PyMongo Tutorial: querying for more than one document, where you can do :
for document in myCollection.find():
print(document) # iterate the cursor
where REGEX would match everything - and it resulted in "Killed".
Unfortunately there's lack of information here to debug on why and what 'Killed' is. Although if you would like to match everything, you can just state:
cursor = db.myCollection.find({"name": {$regex: /.*/}})
Given that field name contains string values. Although using $exists to check whether field name exists would be preferable than using regex.
While the use of $exists operator in your example above is incorrect. You're missing an s in $exists. Again, unfortunately we don't know much information on what 'didn't work' meant to help debug further.
If you're writing this script for Python exercise, I would recommend to review:
PyMongo Tutorial
MongoDB Tutorial: query documents
You could also enrol in a free online course at MongoDB University for M220P: MongoDB for Python Developers.
However, if you are just trying to accomplish your task of exporting CSV from a collection. As an alternative you could just use MongoDB's mongoexport. Which has the support for :
Exporting specific fields via --fields "name,address"
Exporting in CSV via --type "csv"
Exporting specific values with query via --query "..."
See mongoexport usage for more information.
I had no luck with .find().forEach() either, but this should find what you are searching for and then print it.
First find all documents that match what you are searching for
cursors = db.myCollection.find({"name": {$regex: REGEX}})
then iterate it over the matches
for cursor in cursors
print(cursor.get("name"))
The find() methods returns a PyMongo cursor, which is a reference to the result set of a query.
You have to de-reference, somehow, the reference(address).
After that, you will get a better understanding how to manipulate/manage the cursor.
Try the following for a start:
result = db.*collection_name*.find()
print(list(result))
I think I get the question but there's no accurate answer yet I believe. I had the same challenge and that's how I came about this, although, I don't know how to output to a .csv file. For my situation I needed the result in JSON. Here's my solution to your question using mongodb Projections;
your_collection = db.myCollection
cursor = list(your_collection.find( { }, {"name": 1, "address": 1}))
This second line returns the result as a list using the python list() function.
And then you can use jsonify(cursor) or just print(cursor) as a list.
I believe with the list it should be easier to figure how to output to a .csv.
I have tried and tried on Meteor and on Robomongo (Mongodb) to select objects with dot notation.
I would like to be able to filter team.0.wageringStats.wageringStraightSpread objects (sometimes subjects can be fields or arrays - thats another issue)
In the first image I can select team.wageringStats.wageringStraightSpread and get back all the subOjects of team (team has siblings not shown in images)
The second image I tried team.0.wageringStats.wageringStraightSpread and I get no fields.
Lastly i tried team.[0].wageringStats.wageringStraightSpread and
team[0].wageringStats.wageringStraightSpread and get the same result : 0 fields
I am at a loss and would like some help. Thank you
I am not sure what you are trying to do now? Because in your first command, you already have a list of team that match your criteria and then, put it into the loop of meteor to process. Why do you need to find only the first one ? By the way, in order to select the nth of the result set in mongodb, you will need something like skip and limit
db.collections.find({'team.wageringStats.wageringStraightSpread':1}).limit(1).skip(0)
(in skip, you need to pass the offset you need to reach to)
Also, if you only care about the first one, findOne is the one you need to do the query
db.collections.findOne({'team.wageringStats.wageringStraightSpread':1})
Be aware that the syntax of mongodb and meteor for querying is a bit different
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/
What is the status of text search with haskell mongodb driver?
There is now 'LIKE' operator in mongo similar to SQL variants, so what is the best way to search a collection or the whole db for a particular text string?
I've read some people referencing external tools but I can also see that some text search was implemented in 2.4 mongo version which is done through command interface.
There should not be any problems doing it from console but how would I do it from haskell driver? I found 'runCommand' function in the driver APIs and it looks like it should be possible to send 'text' command to the server but the signature shows that it returns only one document - not a list of documents. So how is it done correctly?
How would I efficiently search for a word or a sentence in a collection or db so that it returns a list of documents containing the word? Is it possible to do without external tools using mongo 'text search' feature? SHould it be done in the application level?
Thanks.
The result type already contains the list of documents (that contain the searched text). Unfortunately, I could not test the query on my running database, but I have used runCommand to run an aggregation (before it was implemented for the haskell driver). The result document you get for such an query looks something like this:
{ results: [
{ score : ...,
obj : { ... }
},
...
],
... ,
ok : 1
}
The result document has a field results and its value is a document with fields score and obj. So in the end, you can find each of the matched document behind the obj-field in the list of results.
For more details, you should take a look here.