Friday, January 30, 2015

data: "Append Only Computing", Immutability Changes Everything - Pat Helland (!)
Immutability Changes Everything, Pat Helland,

"It wasn’t that long ago that computation was expensive, disk storage was expensive, DRAM was expensive, but coordination with latches was cheap. Now, all these have changed using cheap computation (with many-core), cheap commodity disks, and cheap DRAM and SSD, while coordination with latches gets harder because latch latency loses lots of instruction opportunities. We can now afford to keep immutable copies of lots of data, and one payoff is reduced coordination challenges."

OldCPU, HDD, RAMCoordinationno duplication
=> DB normalization
NewCoordinationCPU, HDD, RAMno locking
=> no DB updates

"Can not re-write history. Database transaction logs never change. No updates.
A database is a caching of a subset of the log." 

Immutability Changes Everything - Pat Helland, RICON2012 on Vimeo
"There are emerging solutions which are based on immutable data. It seems we need to look back to our grandparents and how they managed distributed work in the days before telephones."

Immutability Changes Everything - Pat Helland, RICON2012 from Basho Technologies on Vimeo.
  • Accountants Don’t Use Erasers (Ledger)
  • Keeping the Stone Tablets Safe
  • Hey! Versions Are Immutable, Too!
  • Immutability by Reference
  • Immutability Is in the Eye of the Beholder
  • Normalization Is for Sissies
"Pat Helland has published another thought provoking paper: Immutability Changes Everything. If video is more your style, Pat gave a wonderful talk on the same subject at RICON2012 (video, slides). It's fun to see how Pat's thinking is evolving over time as he's worked at Tandem Computers (TransactionMonitoring Facility), Amazon, Microsoft (Microsoft Transaction Server and SQL Service Broker), and now Salesforce."

One such database system: Datomic

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