Mapreduce Function In Mongodb

During implementation the map phase is always executed before the reduce phase. Syntax of mongo mapreduce() following is the syntax of mapreduce() function that could be used in mongo shell >db.collection.mapre duce This is a guide to mongodb mapreduce.

The reduce phase performs the aggregations, or analysis over that data. This function has two main functions, i.e., map function and reduce function. This is a guide to mongodb mapreduce.

Viewed 4k times 0 i am trying to return a field of every object in my collection in form of array using mapreduce function.

Here, map operation is performed to each input document. Mapreduce is a programming model and an associated implementation for processing and generating large data sets. To use mapreduce the user need to define a map function which takes a key/value pair and produces an intermediate key/value pair, later a reduce function merges the intermediate results of the same key to produce the. Now, we will use a mapreduce function on the posts collection to select all active posts, group them based on user_name and then count the.