Tomasz Ducin
js / java / py enthusiast, architect & developer, trainer, community activist
Mongodb
aggregation & Map-Reduce
Tomasz Ducin
16th April 2014, Warsaw
plan
- who doesn't know mongo?
- motivation (big data)
- simple aggregation operations
- aggregation framework
- map-reduce
Simple aggregation operations
TOOLS SIMILAR TO SQL (docs)
- count ( dbcmd, collection)
- distinct ( dbcmd, collection)
- group ( dbcmd, collection)
Aggregation framework
aggregating operations
api
db.collection.aggregate([ step_1, step_2, ..., step_n ])-
each step is one of 7 operations
- combining (repetative) operations in any order
- output of one becomes input of another
demo
let's try it out
aggregation fw limitations
https://www.youtube.com/watch?v=8BQzKXI-_wE#t=65
- result set limited to 16MB of memory (the maximum BSON document size is 16MB as well)
- 10% of memory on a machine
- sharding
map-reduce
algorithm
- 3 steps
- map function: scope
- reduce function: ~recursion, common key
Mongodb aggregation & Map-Reduce
By Tomasz Ducin
Mongodb aggregation & Map-Reduce
MongoDB built-in tools for processing data
