How would you recreate its result? Does it use aggregation only? Or with some code?
Aggregation pipeline operators like objectToArray doesn't work with nested key-value. The next easiest way I can think of when dealing with nested key-value is just using the programming language, in my case JavaScript.
What do I have to do in order to get the same result as "analyze" result from "MongoDB Compass > Schema"?
Related
Which one is good mongodb aggregate or mongodb functions
what i mean to say : mongodb aggregation or mongodb functional which one is preforable and which one gives good performance.
Mongodb functions
Defines a custom aggregation function or expression in JavaScript.
Whereas aggregation is a prebuilt supported operations.
Executing JavaScript inside an aggregation expression may decrease performance. Only use the $function operator if the provided pipeline operators cannot fulfill your application's needs.
If you have a logic which needs to be customised not supported out of the box, go for functions.
Reference
Say I have a Mongo aggregation I know that I will use frequently, for example, finding the average of a dataset.
Essentially, I want someone to make an API for the database such that someone could type db.collection.average() in the mongo shell and get the result of that function, so that someone without much knowledge of the aggregation framework would easily be able to get the average (or result of any complicated aggregation function I create). What is the best way to achieve this?
As of MongoDB 3.4, you can create views that wrap a defined aggregation pipeline. Sounds like a perfect fit for your use case.
How to do an aggregation query in MongoDB from the RapidMiner using the mongodb plugin? I've tried to google around, unfortunately with no success at all. It has a direct support for criteria and projection (using operator "Read MongoDB"), however I don't see anyhow support for the aggregation. It does have an "Execute MongoDB Command" operator, which might be capable of doing that but I can't find any extensive examples on how to use it. Eventually, if the above mentioned is not possible, do you know any other way how to do the "unwind" over the data in the RapidMiner having the mongodb collection loaded in?
The Execute MongoDB Command Operator is a wrapper for the mongoDB command db.runCommand(). If you want to continue working in RapidMiner, you can expand the collection you get as a result from the Read MongoDB and transform it into an ExampleSet with the JSON to Data Operator.
MongoDB 3.2 is now providing a filter expression to partially index the collection.
Based on that feature, I wonder how MongoDB could help me for the following case.
I do have many pre defined queries very near the filter expression. The principle will be to create many filter expression index.
The index will in fact keep the ids of the maching document and will be updated on each document changes.
For performance reason, I prefer to use the index engine from MongoDB that trying to use an external tools with Trigger solution.
How could I accomplish such feature by extending MongoDB. Any others noSQL could help ?
Thanks
I wanted to know about some examples or scenarios related to Mongo DB which can be done by map-reduce but not aggregation framework ?
Map-reduce is considered to be very powerful tool/mechanism of aggregating data. Then can some of you please share few scenarios where it is not possible for map-reduce to do it ?
Thanks & Best Regards.
In MongoDB currently aggregation framework is limited to 16MB of returned results.
MapReduce can write its output to a collection and has no size limitations.
MapReduce can group entire documents, aggregation framework works on field level. MapReduce can map keys to values and values to keys which can't be done any other way. MapReduce can also call/use various JavaScript built-in functions where aggregation is limited to functions and expressions which are built-in to its framework.