The median is somewhat tricky to compute in the general case, because it involves sorting the whole data set, or using a recursion with a depth that is also proportional to the data set size. That’s maybe the reason why many databases don’t have a median operator out of the box (MySQL doesn’t have one, … Read more
I had the same issue and was able to fix it by removing the full url (for example: mongodb://myuser:[email protected]/my_database) in the connection tab and only putting in the mongodb server url: mongodb-test.mydomain.com. Next, in the Authentication tab, I checked the Perform authentication checkbox, specified the Database, user name, password. I also added the database in … Read more
The simplest solution to this is to use the mongodb inbuilt $indexStats aggregation stage, added in MongoDB 3.2. Using the Mongo console: db.collection.aggregate([ { $indexStats: { } } ]) Using PyMongo: from pymongo import MongoClient collection = MongoClient()[db_name][collection_name] index_stats = collection.aggregate([{‘$indexStats’:{}}]) for index_info in index_stats: print index_info
There is a distinct command in mongodb, that can be used in conjunction with a query. However, I believe this just returns a distinct list of values for a specific key you name (i.e. in your case, you’d only get the id values returned) so I’m not sure this will give you exactly what you … Read more
Add Stage 2.5 😛 { $project:{ FileName:1, FileSize:{$substr:[“$FileSize”, 0, -1 ]} } } FileSize is a integer and there is no operation to convert it to String. So you can use hack, and use substr to convert it to string, 0 for starting and -1 rest of the string.
var before = new Date() #aggregation query var after = new Date() execution_mills = after – before
I would recommend NOT to make separate collection per user. Read the documentation By default MongoDB has a limit of approximately 24,000 namespaces per database. Each namespace is 628 bytes, the .ns file is 16MB by default. Each collection counts as a namespace, as does each index. Thus if every collection had one index, we … Read more
What you are doing is the best and most optimal way of doing it in Mongo. I am in a similar situation and after going all possible implementations of the N:M design pattern, have also arrived to this same solution. Apparently, This is not a mongodb thing, but more of a concept of NoSQL, wherein, … Read more
I’m not sure I would agree with the sentiment that a lot of people don’t like SPARQL. SPARQL 1.0 did have some short comings, but it quite nicely addressed what it was designed for, and the new iteration, SPARQL 1.1, builds upon it adding many constructs from SQL that people expected to see in the … Read more
Why does not the aggregate output return as a DBCursor or a List? The aggregation framework was created to solve easy problems that otherwise would require map-reduce. This framework is commonly used to compute data that requires the full db as input and few document as output. What is the difference between the $match operator … Read more