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Datomic is Free

blog.datomic.com

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Re: Datomic is Free

#221

Post by augustl »

tyre wrote: post #206
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…

“No real gain” I don’t agree with this. iirc Rack ultimately uses and array to represent HTTP responses. It has three members: the status code, the headers, and the response body. If you’re shipping a new change, is it easier to mistake response[0] or response.headers? This is a trivial example, but the general class (ha) of trade-off is amplified with more complex objects. I love clojure and lisp but the blindness b…

In Clojure, response.headers is still data :) You just use the built-in ways of reading named keys, such as (:headers response) or (get headers :response).

Re: Datomic is Free

#222

Post by LukeEF »

NickBusey wrote: post #2

Free as in beer. Not free as in speech. > Is it Open Source? Datomic binaries are provided under the Apache 2 license which grants all the same rights to a work delivered in object form. Datomic will continue to be developed at Nubank, where it is a critical piece of our infrastructure.

There are already some open source alternatives to datomic. TerminusDB (https://github.com/terminusdb/terminusdb) for example is implemented in prolog (and Rust) so has the datalog variant query power that makes datomic so powerful. If you want free as in speech (thou I love free beer).

Re: Datomic is Free

#223

Post by augustl »

spariev wrote: post #205
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…

One thing which is quite hard to do in Datomic is simple pagination on a large sorted dataset, as one can easily do with LIMIT/OFFSET in MySQL for example. There are solutions for some of the cases, but general case is not solved, as far as I remember (it’s been a while I used it extensively)

It depends! If you want to lazily walk data, you can read directly from the index (keep in mind, the index = the data = lives in your app), or use the index-pull API which is a bit more convenient.

However, if you want to paginate data that you need to sort first, and the data isn't sorted the way you want in the index, you have to read all of the data first, and then sort it. But this is also what a database server would need to do :)

Re: Datomic is Free

#224

Post by bvanderveen »

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 template. Had to write application code to export/reimport prod data from cluster to another—there was no other migration path (and yes, we were talking to their enterprise support).

We migrated to Postgres and are now using a 10th of the compute resources. Our p99 response times went from 1.3-1.5s to under 300ms once all the read traffic was cut over.

Mother Postgres can do no wrong.

Still, Datomic seems like a cool idea.

Re: Datomic is Free

#225

Post by mtnygard »

samuell wrote: post #148

Question to people having used Datomic: Based on experience with Prolog, I always thought using Datalog in a database like Datomic would mean being able to model your data model using stored queries as a very expressive way of creating "classes". And that by modeling your data model using nested such queries, you alleviate the need for an ORM, and all the boilerplate and duplication of defining classes both in SQL an…

You can definitely use Datomic in the way you describe, in at least a few different ways. I haven't often seen queries stored in the database itself. It's more common to have the queries as data in the application. Since queries are ordinary Clojure data structures, it's even more common to see functions that build queries from inputs or functions that transform queries (e.g., adding a tenant-id filter clause).

Datomic also support rules, including recursive rules. I wrote a library to do OWL-style inference about classes of entities using rules. You can see an example here (https://github.com/cognitect-labs/onto/blob/master/src/onto/...). This is a rule that infers all the classes that apply to an entity from an attribute that assigns it one class.

I would also say that building an "entity type definition" system as entities in Datomic is almost the first thing every dev tries after the tutorial. It works... but you almost never _need_ it later.

Re: Datomic is Free

#226

Post by gleenn »

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.

Clojure uses objects for connections and things, but POJOs are harmful IMHO because it makes manipulation and collecting data a bespoke task every time. Every time you change the data, you have to change a class to represent the JSON and the ORM class and .... this is all just data

Re: Datomic is Free

#227

Post by augustl »

riku_iki wrote: post #189
alecco wrote: post #92

Earlier quoted context omitted.

Just the temporal properties alone make it very useful for anything where it matters like billing, finance, inventory. Else you are in views/schema/indexing hell to do it on top of SQL. There is some SQL temporal support but it's not great and varies a lot. Also since it's not native to the storage it has a lot of complexity issues under the rug making it not great. Many financial systems use Event Sourcing (OOP + OR…

> Just the temporal properties alone make it very useful for anything where it matters like billing, finance, inventory. you can easily create datamodel to have this in SQL dbs: create table transaction_history(..., execution_time timestamp);

Fyi, Datomic lets you look at the entire database at any point in time, as an immutable value. Also, you can annotate transactions with metadata, and query for "which tx wrote this specific value for this row/column" and look at custom metadata you added to the tx to reason about your system. Doing all of that in SQL is not trivial, to say the least.

Re: Datomic is Free

#228

Post by brundolf »

kamma4434 wrote: post #201
brundolf wrote: post #177

Earlier quoted context omitted.

Interesting! I assumed Datomic was entirely custom Now I'm even more curious if you could skip Datomic and just do something like this directly with a relational DB in production

Yes, but you end up rewriting Datomic!

Well, except it sounds like Datomic is closed-source :)

Re: Datomic is Free

#229

Post by convolvatron »

spariev wrote: post #205
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…

One thing which is quite hard to do in Datomic is simple pagination on a large sorted dataset, as one can easily do with LIMIT/OFFSET in MySQL for example. There are solutions for some of the cases, but general case is not solved, as far as I remember (it’s been a while I used it extensively)

there must be a relational sort? ah yes, there is, and the ability to feed a relational output into a Clojure sort

Re: Datomic is Free

#230

Post by hoffs »

beders wrote: post #170

Every single day I wish the architects at my current job had chosen Datomic instead of Postgresql. It would have saved us so so much time and trouble. The time traveling ability alone would have been so useful so many times. Also the ability to annotate transactions is awesome. So many goodies. Here's a good summary: https://medium.com/@val.vvalval/what-datomic-brings-to-busin...

I am almost certain you don't.
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