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Datomic is Free

blog.datomic.com

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Re: Datomic is Free

#241

Post by wwweston »

bvanderveen wrote: post #236
JulianWasTaken wrote: post #233

Earlier quoted context omitted.

I don't doubt your story of course, and I love Postgres, but comparing apples to oranges no? Datomic's killer feature is time travel. Did you simply not use that feature once you moved off Datomic (and if so why'd you pick Datomic in the first place)? Or are you using Postgres using some extension to add in?

We implemented it in Postgres with 'created_at' and 'deleted_at' columns on everything and filtering to make sure that the object 'exists' at the time the query is concerned with. Changes in relationships between objects are modeled as join tables with a boolean indicating whether the relationship is made or broken and at what time. Our data model is not large and we had a very complete test suite already, so it was…

Yeah, it seems you could be able to substitute thoughtful schema design avoiding updates/deletes for time-travel as a feature.

I wonder if anyone has made a collection of reference examples implemented this way (and in general think that a substantial compendium good examples of DB schema and thinking behind them could be worthwhile).

Re: Datomic is Free

#242

Post by ithrow »

bvanderveen wrote: post #224

From experience: Datomic Cloud is slow, expensive, resource intensive, designed in the baroque style of massively over-complicated CloudFormation astronautics. Hard to diagnose performance issues. Impossible to backup. Ran into one scenario where apparently we weren't quick enough to migrate to the latest version, AWS had dropped support for $runtime in Lambda, and it became impossible to upgrade the CloudFormation t…

I guess this is why datomic.com front page now defaults to datomic pro and not cloud.

Re: Datomic is Free

#243

Post by waffletower »

kaba0 wrote: post #219
gleenn wrote: post #193

Earlier quoted context omitted.

Rich Hickey has a great talk about how Objects are data structures with unique interfaces that are unnecessary complexity. He showed and example of a web server with a web request object with request headers etc etc. Doing simple things like collecting information out of that nested object structure is bespoke and harder than it should be for no real gain. If everything is a map or list or set, it becomes completely…

I think there is a need for objects. An active connection, talking to the GPU, etc are not data -- identity is essential for their operation. OOP is probably the best way to model such,.. well objects, allowing them a private, encapsulated state, and making it only modifiable, or even viewable through a well-defined public interface that enforces all its invariants.

I think OOP (object oriented programming) is abused and is not the optimal paradigm for most software services. It succeeds best at providing inter-operability structure for API design. "Objects", as mentioned here, are an abstraction. Stateful data can be organized and manipulated elegantly without use of the OOP paradigm. Many small systems that employ OOP hamper their maintenance and extendability by unnecessary dependence upon encapsulation and data ownership. Mutability is a villain here as well -- when data structures are immutable, there is little fear of panoptic architectures designed without ownership constraints. Here software is no longer corralled into walled gardens of "objects"; large complex types and their brittle method associations are avoided, greatly simplifying software architectures as a result.

Re: Datomic is Free

#244

Post by twic »

wwweston wrote: post #241
bvanderveen wrote: post #236

Earlier quoted context omitted.

We implemented it in Postgres with 'created_at' and 'deleted_at' columns on everything and filtering to make sure that the object 'exists' at the time the query is concerned with. Changes in relationships between objects are modeled as join tables with a boolean indicating whether the relationship is made or broken and at what time. Our data model is not large and we had a very complete test suite already, so it was…

Yeah, it seems you could be able to substitute thoughtful schema design avoiding updates/deletes for time-travel as a feature. I wonder if anyone has made a collection of reference examples implemented this way (and in general think that a substantial compendium good examples of DB schema and thinking behind them could be worthwhile).

I'm moderately confident you could mechanically transform a time-oblivious schema into a history-preserving one, and then write a view on top of it which gave a slice at a particular time. Moderately.

Re: Datomic is Free

#245

Post by ithrow »

Scarbutt wrote: post #104
augustl wrote: post #11

Datomic's is perfect for probably 90% of small-ish backoffice systems that never has to be web scale (i.e. most of what I do at work). Writing in a single thread removes a whole host of problems in understanding (and implementing) how data changes over time. (And a busy MVCC sql db spends 75% of its time doing coordination, not actual writes, so a single thread applying a queue of transactions in sequence can be fast…

Datomic's is perfect for probably 90% of small-ish backoffice systems that never has to be web scale How do they scale it for Nubank? (millions of users)

I don't how they do it, but the obvious answer is probably sharding. Their cloud costs must be no joke. Peers require tons of memory and I can only guess they must have thousands of transactors to support that workload and who knows how many peers. Add to this that they probably need something like Kafka for integrating/pipelining all this data.

Re: Datomic is Free

#246

Post by newswasboring »

thomastjeffery wrote: post #239
newswasboring wrote: post #237

Earlier quoted context omitted.

I don't know what you are calling "good". That is a super loaded word. I would say it is effective though. The baseline evidence for that is how much money gets spent in that industry, I guess.

> The baseline evidence for that is how much money gets spent in that industry, I guess. I can't imagine a clearer example of circular reasoning. I can lift exactly as much weight as I decide to put on the barbell.

While I see your point, please note people actually spending money don't just look at how much money is in the industry. They have internal metrics and can track performance of individual marketing campaigns. I called it a baseline argument because I'm not a marketing expert so this it the only real KPI __I__ understand.

Re: Datomic is Free

#247

Post by JimmyRuska »

augustl wrote: post #11

Datomic's is perfect for probably 90% of small-ish backoffice systems that never has to be web scale (i.e. most of what I do at work). Writing in a single thread removes a whole host of problems in understanding (and implementing) how data changes over time. (And a busy MVCC sql db spends 75% of its time doing coordination, not actual writes, so a single thread applying a queue of transactions in sequence can be fast…

> doing UPDATE in SQL feels pretty weird, as the default mode of operation of your _business data_ is to delete data, with no trace of who and why!

It's a good idea to version your schema changes using something like liquibase into git, that gets rid of at least some of those pains. Liquibase works on a wide variety of databases, even graphs like Neo4j

I got the same feeling in Erlang many times, once write operations start getting parallel you worry about atomic operations, and making an Erlang process centralize writes through its message queue always feels natural and easy to reason about.

Re: Datomic is Free

#248

Post by avodonosov »

bvanderveen wrote: post #224

From experience: Datomic Cloud is slow, expensive, resource intensive, designed in the baroque style of massively over-complicated CloudFormation astronautics. Hard to diagnose performance issues. Impossible to backup. Ran into one scenario where apparently we weren't quick enough to migrate to the latest version, AWS had dropped support for $runtime in Lambda, and it became impossible to upgrade the CloudFormation t…

Why backups were impossible? Couldn't you backed up the storage resources?

Re: Datomic is Free

#249

Post by ithrow »

JulianWasTaken wrote: post #233
bvanderveen wrote: post #224

From experience: Datomic Cloud is slow, expensive, resource intensive, designed in the baroque style of massively over-complicated CloudFormation astronautics. Hard to diagnose performance issues. Impossible to backup. Ran into one scenario where apparently we weren't quick enough to migrate to the latest version, AWS had dropped support for $runtime in Lambda, and it became impossible to upgrade the CloudFormation t…

I don't doubt your story of course, and I love Postgres, but comparing apples to oranges no? Datomic's killer feature is time travel. Did you simply not use that feature once you moved off Datomic (and if so why'd you pick Datomic in the first place)? Or are you using Postgres using some extension to add in?

Datomic's 'time travel' is an audit feature, not something for your application/business logic to depend on. Performance reasons make it impractical, unless you only have like 10 users and very little data.
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