Simon Willison’s Weblog

The humble hash aggregate (via) Today I learned that “hash aggregate” is the name for the algorithm where you split a list of tuples on a common key, run an aggregation against each resulting group and combine the results back together again—I’d previously thought if this in terms of map/reduce but hash aggregate is a much older term used widely by SQL engines—I’ve seen it come up in PostgreSQL explain query output (for GROUP BY) before but didn’t know what it meant.

# 6th June 2021, 4:03 pm / mapreduce, sql, algorithms

The Friendship That Made Google Huge. The New Yorker profiles Jeff Dean and Sanjay Ghemawat, Google’s first and only level 11 Senior Fellows. This is some of the best writing on complex software engineering topics (map-reduce, Tensor Flow and the like) aimed at a general audience that I’ve ever seen. Also a very compelling case study in pair programming.

# 31st December 2018, 3:56 am / mapreduce, tensorflow, google, new-yorker

App Engine at Google I/O 2010. OpenID and OAuth are now baked in to the AppEngine users API. They’re also demoing two very exciting new features—a mapper API for doing map/reduce style queries against the data store, and a Channel API for building comet applications.

# 20th May 2010, 3:30 pm / appengine, comet, google, mapreduce, oauth, openid, recovered

BashReduce. Map/Reduce in Bash is no longer a joke project (if it ever was)—Richard Crowley is extending it and using it for analysis at OpenDNS.

# 28th June 2009, 3:03 pm / mapreduce, bash, bashreduce, richard-crowley, opendns

Finding similar items with Amazon Elastic MapReduce, Python, and Hadoop streaming. Tutorial for running Hadoop jobs on Elastic MapReduce using Python and the 2005 Audioscrobbler dataset.

# 7th April 2009, 9:19 am / audioscrobbler, amazon, amazon-web-services, hadoop, mapreduce, elasticmapreduce, python

Amazon Elastic MapReduce (via) Hadoop as a service. Basically a web based GUI around Hadoop—you could roll this yourself on EC2 but for a small markup on regular EC2 prices you get to avoid the extra work setting everything up. Data processing scripts can be written in Java, Ruby, Perl, Python, PHP, R, or C++ and are loaded in to S3 before firing off the job.

# 2nd April 2009, 10:25 am / cloud-computing, hadoop, amazon-web-services, amazon, mapreduce, ec2, s3

Cascading. A Java API abstraction layer over Hadoop that lets developers think in terms of pipes and filters rather than map/reduce. The Cascading developers claim that this model is easier to understand and less error prone.

# 1st October 2008, 1:22 pm / mapreduce, cascading, java, hadoop, pipesfilters

Python + Hadoop = Flying Circus Elephant. Last.fm have released Dumbo, a Python module that lets you easily write Hadoop map/reduce tasks using Python and generators.

# 31st May 2008, 2:14 pm / hadoop, python, generators, lastfm, dumbo, mapreduce

Writing An Hadoop MapReduce Program In Python. Hadoop (the open source map/reduce framework) can interact with any program that reads from stdin and outputs on stdout—so it’s trivial to drop in Python scripts for the map and reduce steps.

# 9th October 2007, 11:33 am / hadoop, mapreduce, python

CouchDB: Thinking beyond the RDBMS. CouchDB is a fascinating project—an Erlang powered non-relational database with a JSON API that lets you define “views” (really computed tables) based on JavaScript functions that execute using map/reduce. Damien Katz, the main developer currently works for MySQL and used to work on Lotus Notes.

# 3rd September 2007, 9:48 am / couchdb, erlang, databases, json, javascript, damien-katz, lotusnotes, mysql, mapreduce