date: 2024-09-17
title: "Map Reduce"
status: DONE
author:
- AllenYGY
tags:
- NOTE
- Data-Analysis
publish: TrueMap Reduce
- Input: a set of key-value pairs
- Programmer specifies two methods:
- Map: (k1, v1) -> (k, v)
- Takes a key-value pair and outputs a set of key-value pairs
- E.g., key is the filename, value is a single line in the file
- Reduce: (k, list(v)) -> list(v)
- All values v' with same key k' are reduced together and processed in v' order
- There is one Reduce function call per unique key k'
- Map: (k1, v1) -> (k, v)
Example Natural Join
Table Of Contents