No, I think it's critical. I worked on one of the first services to ever use Spanner when I was an intern. Lock-free read transactions is a game changer. Short answer -- if your database system can't do lock-free reads, your database is broken. That one feature allows one to do some incredible performance optimizations.

What _exactly_ is a lock-free read transaction? Is it different to reading in a MVCC system?

>if your database system can't do lock-free reads, your database is broken

Yep.

I know CouchDB doesn't do read locking. What are other ones out there?

Not doing read locking is not a game-changer.

Firebird doesn't do read locking. Neither does Lotus Notes. Both have been around about 20 years.

Not doing read locking alone. Combine it with a planet-scale data storage system...

Postgres and Oracle?

PostgreSQL uses MVCC to ensure ACID compliance without read locks. Uncommitted concurrent transactions are isolated from each other.

Datomic.

"non-blocking reads in the past"

Sounds like google's finally invented time travel.

Actually, this is exactly how transactions in Oracle work. The difference is - one db server (Oracle) vs. distributed system (Google)

Oracle doesn't have to be one DB server. Check out Oracle RAC for instance.

I would also be interested in a longer, elaborated answer.

The lessons are pretty much the same as the ones functional programming have been trying to teach us for years: immutability and caching.

Beyond that I would rather not elaborate for reasons of confidentiality.

Value addressing. MVCC.

What is "value addressing"? That's the first time I've seen that term and google doesn't bring anything relevant up.

This is a wild guess, but I guess it might be a synonym for content addressing

http://en.wikipedia.org/wiki/Content-addressable_storage#Con...

+1. Neologism of an autodidact. IMHO it is more correct, regardless.

Elaborate?

> It is too bad that Ken Thompson didn't get at least acknowledged for his role in making it happen.

Interesting, can you say more about this?

Is he not mentioned because officially he is part of the Go team?

Ken sat near Jeff, Sanjay, and co while they were designing Spanner, and he regularly consults in an informal capacity on people's projects. I wasn't there, but it wouldn't surprise me at all if Ken's unique insight contributed to Spanner's design.

I'm familiar with Ken Thompson, so I'm more puzzled than someone who isn't familiar with his work might be.

What exactly is his unique insight? Do you know any specifics or are you just speaking on behalf of the fact that he's a famous programmer?

I say this as someone whose Planetside2 character is named: "KenThompsonHackerExtraordinaire"

Enneff works with ken in the Go team at Google.

As for his particular insight, if you are familiar with his work, that should be enough.

For those not familiar with his work, this interview might be a good starting point:

http://genius.cat-v.org/ken-thompson/interviews/unix-and-bey...

This is golden:

"The aggressive use of a small number of abstractions is, I think, the direct result of a very small number of people who interact closely during the implementation."

It's from 1997 I guess ? Seems like he was wrong about Linux and maybe Microsoft :)

Ken's mind just works in a different way to most people. You explain your problem to him and he'll respond with some question or statement that turns your entire perspective inside out.

When I was in the platforms group looking at storage issues the Spanner requirements had a lot of commentary from Ken in them, so much so that I thought it was his idea/project until someone corrected me a bit later. That was why I was surprised he wasn't acknowledged, from where I sat it seemed like he was one of the architects of the effort. Apparently that wasn't the case.